/*
 *  Licensed to the Apache Software Foundation (ASF) under one
 *  or more contributor license agreements.  See the NOTICE file
 *  distributed with this work for additional information
 *  regarding copyright ownership.  The ASF licenses this file
 *  to you under the Apache License, Version 2.0 (the
 *  "License"); you may not use this file except in compliance
 *  with the License.  You may obtain a copy of the License at
 *  
 *    http://www.apache.org/licenses/LICENSE-2.0
 *  
 *  Unless required by applicable law or agreed to in writing,
 *  software distributed under the License is distributed on an
 *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 *  KIND, either express or implied.  See the License for the
 *  specific language governing permissions and limitations
 *  under the License. 
 *  
 */
package org.apache.directory.shared.ldap.util;


import java.io.File;

import org.apache.directory.shared.i18n.I18n;


/**
 * <p>
 * Helpers for <code>java.lang.System</code>.
 * </p>
 * <p>
 * If a system property cannot be read due to security restrictions, the
 * corresponding field in this class will be set to <code>null</code> and a
 * message will be written to <code>System.err</code>.
 * </p>
 * 
 * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
 */
public class SystemUtils
{

    /**
     * The prefix String for all Windows OS.
     */
    private static final String OS_NAME_WINDOWS_PREFIX = "Windows";

    // System property constants
    // -----------------------------------------------------------------------
    // These MUST be declared first. Other constants depend on this.

    /**
     * The System property key for the user home directory.
     */
    private static final String USER_HOME_KEY = "user.home";

    /**
     * The System property key for the user directory.
     */
    private static final String USER_DIR_KEY = "user.dir";

    /**
     * The System property key for the Java IO temporary directory.
     */
    private static final String JAVA_IO_TMPDIR_KEY = "java.io.tmpdir";

    /**
     * The System property key for the Java home directory.
     */
    private static final String JAVA_HOME_KEY = "java.home";

    /**
     * <p>
     * The <code>awt.toolkit</code> System Property.
     * </p>
     * <p>
     * Holds a class name, on Windows XP this is
     * <code>sun.awt.windows.WToolkit</code>.
     * </p>
     * <p>
     * <b>On platforms without a GUI, this value is <code>null</code>.</b>
     * </p>
     * <p>
     * Defaults to <code>null</code> if the runtime does not have security
     * access to read this property or the property does not exist.
     * </p>
     * <p>
     * This value is initialized when the class is loaded. If
     * {@link System#setProperty(String,String)} or
     * {@link System#setProperties(java.util.Properties)} is called after this
     * class is loaded, the value will be out of sync with that System property.
     * </p>
     * 
     * @since 2.1
     */
    public static final String AWT_TOOLKIT = getSystemProperty( "awt.toolkit" );

    /**
     * <p>
     * The <code>file.encoding</code> System Property.
     * </p>
     * <p>
     * File encoding, such as <code>Cp1252</code>.
     * </p>
     * <p>
     * Defaults to <code>null</code> if the runtime does not have security
     * access to read this property or the property does not exist.
     * </p>
     * <p>
     * This value is initialized when the class is loaded. If
     * {@link System#setProperty(String,String)} or
     * {@link System#setProperties(java.util.Properties)} is called after this
     * class is loaded, the value will be out of sync with that System property.
     * </p>
     * 
     * @since 2.0
     * @since Java 1.2
     */
    public static final String FILE_ENCODING = getSystemProperty( "file.encoding" );

    /**
     * <p>
     * The <code>file.separator</code> System Property. File separator (<code>&quot;/&quot;</code>
     * on UNIX).
     * </p>
     * <p>
     * Defaults to <code>null</code> if the runtime does not have security
     * access to read this property or the property does not exist.
     * </p>
     * <p>
     * This value is initialized when the class is loaded. If
     * {@link System#setProperty(String,String)} or
     * {@link System#setProperties(java.util.Properties)} is called after this
     * class is loaded, the value will be out of sync with that System property.
     * </p>
     * 
     * @since Java 1.1
     */
    public static final String FILE_SEPARATOR = getSystemProperty( "file.separator" );

    /**
     * <p>
     * The <code>java.awt.fonts</code> System Property.
     * </p>
     * <p>
     * Defaults to <code>null</code> if the runtime does not have security
     * access to read this property or the property does not exist.
     * </p>
     * <p>
     * This value is initialized when the class is loaded. If
     * {@link System#setProperty(String,String)} or
     * {@link System#setProperties(java.util.Properties)} is called after this
     * class is loaded, the value will be out of sync with that System property.
     * </p>
     * 
     * @since 2.1
     */
    public static final String JAVA_AWT_FONTS = getSystemProperty( "java.awt.fonts" );

    /**
     * <p>
     * The <code>java.awt.graphicsenv</code> System Property.
     * </p>
     * <p>
     * Defaults to <code>null</code> if the runtime does not have security
     * access to read this property or the property does not exist.
     * </p>
     * <p>
     * This value is initialized when the class is loaded. If
     * {@link System#setProperty(String,String)} or
     * {@link System#setProperties(java.util.Properties)} is called after this
     * class is loaded, the value will be out of sync with that System property.
     * </p>
     * 
     * @since 2.1
     */
    public static final String JAVA_AWT_GRAPHICSENV = getSystemProperty( "java.awt.graphicsenv" );

    /**
     * <p>
     * The <code>java.awt.headless</code> System Property. The value of this
     * property is the String <code>"true"</code> or <code>"false"</code>.
     * </p>
     * <p>
     * Defaults to <code>null</code> if the runtime does not have security
     * access to read this property or the property does not exist.
     * </p>
     * <p>
     * This value is initialized when the class is loaded. If
     * {@link System#setProperty(String,String)} or
     * {@link System#setProperties(java.util.Properties)} is called after this
     * class is loaded, the value will be out of sync with that System property.
     * </p>
     * 
     * @see #isJavaAwtHeadless()
     * @since 2.1
     * @since Java 1.4
     */
    public static final String JAVA_AWT_HEADLESS = getSystemProperty( "java.awt.headless" );

    /**
     * <p>
     * The <code>java.awt.printerjob</code> System Property.
     * </p>
     * <p>
     * Defaults to <code>null</code> if the runtime does not have security
     * access to read this property or the property does not exist.
     * </p>
     * <p>
     * This value is initialized when the class is loaded. If
     * {@link System#setProperty(String,String)} or
     * {@link System#setProperties(java.util.Properties)} is called after this
     * class is loaded, the value will be out of sync with that System property.
     * </p>
     * 
     * @since 2.1
     */
    public static final String JAVA_AWT_PRINTERJOB = getSystemProperty( "java.awt.printerjob" );

    /**
     * <p>
     * The <code>java.class.path</code> System Property. Java class path.
     * </p>
     * <p>
     * Defaults to <code>null</code> if the runtime does not have security
     * access to read this property or the property does not exist.
     * </p>
     * <p>
     * This value is initialized when the class is loaded. If
     * {@link System#setProperty(String,String)} or
     * {@link System#setProperties(java.util.Properties)} is called after this
     * class is loaded, the value will be out of sync with that System property.
     * </p>
     * 
     * @since Java 1.1
     */
    public static final String JAVA_CLASS_PATH = getSystemProperty( "java.class.path" );

    /**
     * <p>
     * The <code>java.class.version</code> System Property. Java class format
     * version number.
     * </p>
     * <p>
     * Defaults to <code>null</code> if the runtime does not have security
     * access to read this property or the property does not exist.
     * </p>
     * <p>
     * This value is initialized when the class is loaded. If
     * {@link System#setProperty(String,String)} or
     * {@link System#setProperties(java.util.Properties)} is called after this
     * class is loaded, the value will be out of sync with that System property.
     * </p>
     * 
     * @since Java 1.1
     */
    public static final String JAVA_CLASS_VERSION = getSystemProperty( "java.class.version" );

    /**
     * <p>
     * The <code>java.compiler</code> System Property. Name of JIT compiler to
     * use. First in JDK version 1.2. Not used in Sun JDKs after 1.2.
     * </p>
     * <p>
     * Defaults to <code>null</code> if the runtime does not have security
     * access to read this property or the property does not exist.
     * </p>
     * <p>
     * This value is initialized when the class is loaded. If
     * {@link System#setProperty(String,String)} or
     * {@link System#setProperties(java.util.Properties)} is called after this
     * class is loaded, the value will be out of sync with that System property.
     * </p>
     * 
     * @since Java 1.2. Not used in Sun versions after 1.2.
     */
    public static final String JAVA_COMPILER = getSystemProperty( "java.compiler" );

    /**
     * <p>
     * The <code>java.endorsed.dirs</code> System Property. Path of endorsed
     * directory or directories.
     * </p>
     * <p>
     * Defaults to <code>null</code> if the runtime does not have security
     * access to read this property or the property does not exist.
     * </p>
     * <p>
     * This value is initialized when the class is loaded. If
     * {@link System#setProperty(String,String)} or
     * {@link System#setProperties(java.util.Properties)} is called after this
     * class is loaded, the value will be out of sync with that System property.
     * </p>
     * 
     * @since Java 1.4
     */
    public static final String JAVA_ENDORSED_DIRS = getSystemProperty( "java.endorsed.dirs" );

    /**
     * <p>
     * The <code>java.ext.dirs</code> System Property. Path of extension
     * directory or directories.
     * </p>
     * <p>
     * Defaults to <code>null</code> if the runtime does not have security
     * access to read this property or the property does not exist.
     * </p>
     * <p>
     * This value is initialized when the class is loaded. If
     * {@link System#setProperty(String,String)} or
     * {@link System#setProperties(java.util.Properties)} is called after this
     * class is loaded, the value will be out of sync with that System property.
     * </p>
     * 
     * @since Java 1.3
     */
    public static final String JAVA_EXT_DIRS = getSystemProperty( "java.ext.dirs" );

    /**
     * <p>
     * The <code>java.home</code> System Property. Java installation
     * directory.
     * </p>
     * <p>
     * Defaults to <code>null</code> if the runtime does not have security
     * access to read this property or the property does not exist.
     * </p>
     * <p>
     * This value is initialized when the class is loaded. If
     * {@link System#setProperty(String,String)} or
     * {@link System#setProperties(java.util.Properties)} is called after this
     * class is loaded, the value will be out of sync with that System property.
     * </p>
     * 
     * @since Java 1.1
     */
    public static final String JAVA_HOME = getSystemProperty( JAVA_HOME_KEY );

    /**
     * <p>
     * The <code>java.io.tmpdir</code> System Property. Default temp file
     * path.
     * </p>
     * <p>
     * Defaults to <code>null</code> if the runtime does not have security
     * access to read this property or the property does not exist.
     * </p>
     * <p>
     * This value is initialized when the class is loaded. If
     * {@link System#setProperty(String,String)} or
     * {@link System#setProperties(java.util.Properties)} is called after this
     * class is loaded, the value will be out of sync with that System property.
     * </p>
     * 
     * @since Java 1.2
     */
    public static final String JAVA_IO_TMPDIR = getSystemProperty( JAVA_IO_TMPDIR_KEY );

    /**
     * <p>
     * The <code>java.library.path</code> System Property. List of paths to
     * search when loading libraries.
     * </p>
     * <p>
     * Defaults to <code>null</code> if the runtime does not have security
     * access to read this property or the property does not exist.
     * </p>
     * <p>
     * This value is initialized when the class is loaded. If
     * {@link System#setProperty(String,String)} or
     * {@link System#setProperties(java.util.Properties)} is called after this
     * class is loaded, the value will be out of sync with that System property.
     * </p>
     * 
     * @since Java 1.2
     */
    public static final String JAVA_LIBRARY_PATH = getSystemProperty( "java.library.path" );

    /**
     * <p>
     * The <code>java.runtime.name</code> System Property. Java Runtime
     * Environment name.
     * </p>
     * <p>
     * Defaults to <code>null</code> if the runtime does not have security
     * access to read this property or the property does not exist.
     * </p>
     * <p>
     * This value is initialized when the class is loaded. If
     * {@link System#setProperty(String,String)} or
     * {@link System#setProperties(java.util.Properties)} is called after this
     * class is loaded, the value will be out of sync with that System property.
     * </p>
     * 
     * @since 2.0
     * @since Java 1.3
     */
    public static final String JAVA_RUNTIME_NAME = getSystemProperty( "java.runtime.name" );

    /**
     * <p>
     * The <code>java.runtime.version</code> System Property. Java Runtime
     * Environment version.
     * </p>
     * <p>
     * Defaults to <code>null</code> if the runtime does not have security
     * access to read this property or the property does not exist.
     * </p>
     * <p>
     * This value is initialized when the class is loaded. If
     * {@link System#setProperty(String,String)} or
     * {@link System#setProperties(java.util.Properties)} is called after this
     * class is loaded, the value will be out of sync with that System property.
     * </p>
     * 
     * @since 2.0
     * @since Java 1.3
     */
    public static final String JAVA_RUNTIME_VERSION = getSystemProperty( "java.runtime.version" );

    /**
     * <p>
     * The <code>java.specification.name</code> System Property. Java Runtime
     * Environment specification name.
     * </p>
     * <p>
     * Defaults to <code>null</code> if the runtime does not have security
     * access to read this property or the property does not exist.
     * </p>
     * <p>
     * This value is initialized when the class is loaded. If
     * {@link System#setProperty(String,String)} or
     * {@link System#setProperties(java.util.Properties)} is called after this
     * class is loaded, the value will be out of sync with that System property.
     * </p>
     * 
     * @since Java 1.2
     */
    public static final String JAVA_SPECIFICATION_NAME = getSystemProperty( "java.specification.name" );

    /**
     * <p>
     * The <code>java.specification.vendor</code> System Property. Java
     * Runtime Environment specification vendor.
     * </p>
     * <p>
     * Defaults to <code>null</code> if the runtime does not have security
     * access to read this property or the property does not exist.
     * </p>
     * <p>
     * This value is initialized when the class is loaded. If
     * {@link System#setProperty(String,String)} or
     * {@link System#setProperties(java.util.Properties)} is called after this
     * class is loaded, the value will be out of sync with that System property.
     * </p>
     * 
     * @since Java 1.2
     */
    public static final String JAVA_SPECIFICATION_VENDOR = getSystemProperty( "java.specification.vendor" );

    /**
     * <p>
     * The <code>java.specification.version</code> System Property. Java
     * Runtime Environment specification version.
     * </p>
     * <p>
     * Defaults to <code>null</code> if the runtime does not have security
     * access to read this property or the property does not exist.
     * </p>
     * <p>
     * This value is initialized when the class is loaded. If
     * {@link System#setProperty(String,String)} or
     * {@link System#setProperties(java.util.Properties)} is called after this
     * class is loaded, the value will be out of sync with that System property.
     * </p>
     * 
     * @since Java 1.3
     */
    public static final String JAVA_SPECIFICATION_VERSION = getSystemProperty( "java.specification.version" );

    /**
     * <p>
     * The <code>java.util.prefs.PreferencesFactory</code> System Property. A
     * class name.
     * </p>
     * <p>
     * Defaults to <code>null</code> if the runtime does not have security
     * access to read this property or the property does not exist.
     * </p>
     * <p>
     * This value is initialized when the class is loaded. If
     * {@link System#setProperty(String,String)} or
     * {@link System#setProperties(java.util.Properties)} is called after this
     * class is loaded, the value will be out of sync with that System property.
     * </p>
     * 
     * @since 2.1
     * @since Java 1.4
     */
    public static final String JAVA_UTIL_PREFS_PREFERENCES_FACTORY = getSystemProperty( "java.util.prefs.PreferencesFactory" );

    /**
     * <p>
     * The <code>java.vendor</code> System Property. Java vendor-specific
     * string.
     * </p>
     * <p>
     * Defaults to <code>null</code> if the runtime does not have security
     * access to read this property or the property does not exist.
     * </p>
     * <p>
     * This value is initialized when the class is loaded. If
     * {@link System#setProperty(String,String)} or
     * {@link System#setProperties(java.util.Properties)} is called after this
     * class is loaded, the value will be out of sync with that System property.
     * </p>
     * 
     * @since Java 1.1
     */
    public static final String JAVA_VENDOR = getSystemProperty( "java.vendor" );

    /**
     * <p>
     * The <code>java.vendor.url</code> System Property. Java vendor URL.
     * </p>
     * <p>
     * Defaults to <code>null</code> if the runtime does not have security
     * access to read this property or the property does not exist.
     * </p>
     * <p>
     * This value is initialized when the class is loaded. If
     * {@link System#setProperty(String,String)} or
     * {@link System#setProperties(java.util.Properties)} is called after this
     * class is loaded, the value will be out of sync with that System property.
     * </p>
     * 
     * @since Java 1.1
     */
    public static final String JAVA_VENDOR_URL = getSystemProperty( "java.vendor.url" );

    /**
     * <p>
     * The <code>java.version</code> System Property. Java version number.
     * </p>
     * <p>
     * Defaults to <code>null</code> if the runtime does not have security
     * access to read this property or the property does not exist.
     * </p>
     * <p>
     * This value is initialized when the class is loaded. If
     * {@link System#setProperty(String,String)} or
     * {@link System#setProperties(java.util.Properties)} is called after this
     * class is loaded, the value will be out of sync with that System property.
     * </p>
     * 
     * @since Java 1.1
     */
    public static final String JAVA_VERSION = getSystemProperty( "java.version" );

    /**
     * <p>
     * The <code>java.vm.info</code> System Property. Java Virtual Machine
     * implementation info.
     * </p>
     * <p>
     * Defaults to <code>null</code> if the runtime does not have security
     * access to read this property or the property does not exist.
     * </p>
     * <p>
     * This value is initialized when the class is loaded. If
     * {@link System#setProperty(String,String)} or
     * {@link System#setProperties(java.util.Properties)} is called after this
     * class is loaded, the value will be out of sync with that System property.
     * </p>
     * 
     * @since 2.0
     * @since Java 1.2
     */
    public static final String JAVA_VM_INFO = getSystemProperty( "java.vm.info" );

    /**
     * <p>
     * The <code>java.vm.name</code> System Property. Java Virtual Machine
     * implementation name.
     * </p>
     * <p>
     * Defaults to <code>null</code> if the runtime does not have security
     * access to read this property or the property does not exist.
     * </p>
     * <p>
     * This value is initialized when the class is loaded. If
     * {@link System#setProperty(String,String)} or
     * {@link System#setProperties(java.util.Properties)} is called after this
     * class is loaded, the value will be out of sync with that System property.
     * </p>
     * 
     * @since Java 1.2
     */
    public static final String JAVA_VM_NAME = getSystemProperty( "java.vm.name" );

    /**
     * <p>
     * The <code>java.vm.specification.name</code> System Property. Java
     * Virtual Machine specification name.
     * </p>
     * <p>
     * Defaults to <code>null</code> if the runtime does not have security
     * access to read this property or the property does not exist.
     * </p>
     * <p>
     * This value is initialized when the class is loaded. If
     * {@link System#setProperty(String,String)} or
     * {@link System#setProperties(java.util.Properties)} is called after this
     * class is loaded, the value will be out of sync with that System property.
     * </p>
     * 
     * @since Java 1.2
     */
    public static final String JAVA_VM_SPECIFICATION_NAME = getSystemProperty( "java.vm.specification.name" );

    /**
     * <p>
     * The <code>java.vm.specification.vendor</code> System Property. Java
     * Virtual Machine specification vendor.
     * </p>
     * <p>
     * Defaults to <code>null</code> if the runtime does not have security
     * access to read this property or the property does not exist.
     * </p>
     * <p>
     * This value is initialized when the class is loaded. If
     * {@link System#setProperty(String,String)} or
     * {@link System#setProperties(java.util.Properties)} is called after this
     * class is loaded, the value will be out of sync with that System property.
     * </p>
     * 
     * @since Java 1.2
     */
    public static final String JAVA_VM_SPECIFICATION_VENDOR = getSystemProperty( "java.vm.specification.vendor" );

    /**
     * <p>
     * The <code>java.vm.specification.version</code> System Property. Java
     * Virtual Machine specification version.
     * </p>
     * <p>
     * Defaults to <code>null</code> if the runtime does not have security
     * access to read this property or the property does not exist.
     * </p>
     * <p>
     * This value is initialized when the class is loaded. If
     * {@link System#setProperty(String,String)} or
     * {@link System#setProperties(java.util.Properties)} is called after this
     * class is loaded, the value will be out of sync with that System property.
     * </p>
     * 
     * @since Java 1.2
     */
    public static final String JAVA_VM_SPECIFICATION_VERSION = getSystemProperty( "java.vm.specification.version" );

    /**
     * <p>
     * The <code>java.vm.vendor</code> System Property. Java Virtual Machine
     * implementation vendor.
     * </p>
     * <p>
     * Defaults to <code>null</code> if the runtime does not have security
     * access to read this property or the property does not exist.
     * </p>
     * <p>
     * This value is initialized when the class is loaded. If
     * {@link System#setProperty(String,String)} or
     * {@link System#setProperties(java.util.Properties)} is called after this
     * class is loaded, the value will be out of sync with that System property.
     * </p>
     * 
     * @since Java 1.2
     */
    public static final String JAVA_VM_VENDOR = getSystemProperty( "java.vm.vendor" );

    /**
     * <p>
     * The <code>java.vm.version</code> System Property. Java Virtual Machine
     * implementation version.
     * </p>
     * <p>
     * Defaults to <code>null</code> if the runtime does not have security
     * access to read this property or the property does not exist.
     * </p>
     * <p>
     * This value is initialized when the class is loaded. If
     * {@link System#setProperty(String,String)} or
     * {@link System#setProperties(java.util.Properties)} is called after this
     * class is loaded, the value will be out of sync with that System property.
     * </p>
     * 
     * @since Java 1.2
     */
    public static final String JAVA_VM_VERSION = getSystemProperty( "java.vm.version" );

    /**
     * <p>
     * The <code>line.separator</code> System Property. Line separator (<code>&quot;\n<&quot;</code>
     * on UNIX).
     * </p>
     * <p>
     * Defaults to <code>null</code> if the runtime does not have security
     * access to read this property or the property does not exist.
     * </p>
     * <p>
     * This value is initialized when the class is loaded. If
     * {@link System#setProperty(String,String)} or
     * {@link System#setProperties(java.util.Properties)} is called after this
     * class is loaded, the value will be out of sync with that System property.
     * </p>
     * 
     * @since Java 1.1
     */
    public static final String LINE_SEPARATOR = getSystemProperty( "line.separator" );

    /**
     * <p>
     * The <code>os.arch</code> System Property. Operating system
     * architecture.
     * </p>
     * <p>
     * Defaults to <code>null</code> if the runtime does not have security
     * access to read this property or the property does not exist.
     * </p>
     * <p>
     * This value is initialized when the class is loaded. If
     * {@link System#setProperty(String,String)} or
     * {@link System#setProperties(java.util.Properties)} is called after this
     * class is loaded, the value will be out of sync with that System property.
     * </p>
     * 
     * @since Java 1.1
     */
    public static final String OS_ARCH = getSystemProperty( "os.arch" );

    /**
     * <p>
     * The <code>os.name</code> System Property. Operating system name.
     * </p>
     * <p>
     * Defaults to <code>null</code> if the runtime does not have security
     * access to read this property or the property does not exist.
     * </p>
     * <p>
     * This value is initialized when the class is loaded. If
     * {@link System#setProperty(String,String)} or
     * {@link System#setProperties(java.util.Properties)} is called after this
     * class is loaded, the value will be out of sync with that System property.
     * </p>
     * 
     * @since Java 1.1
     */
    public static final String OS_NAME = getSystemProperty( "os.name" );

    /**
     * <p>
     * The <code>os.version</code> System Property. Operating system version.
     * </p>
     * <p>
     * Defaults to <code>null</code> if the runtime does not have security
     * access to read this property or the property does not exist.
     * </p>
     * <p>
     * This value is initialized when the class is loaded. If
     * {@link System#setProperty(String,String)} or
     * {@link System#setProperties(java.util.Properties)} is called after this
     * class is loaded, the value will be out of sync with that System property.
     * </p>
     * 
     * @since Java 1.1
     */
    public static final String OS_VERSION = getSystemProperty( "os.version" );

    /**
     * <p>
     * The <code>path.separator</code> System Property. Path separator (<code>&quot;:&quot;</code>
     * on UNIX).
     * </p>
     * <p>
     * Defaults to <code>null</code> if the runtime does not have security
     * access to read this property or the property does not exist.
     * </p>
     * <p>
     * This value is initialized when the class is loaded. If
     * {@link System#setProperty(String,String)} or
     * {@link System#setProperties(java.util.Properties)} is called after this
     * class is loaded, the value will be out of sync with that System property.
     * </p>
     * 
     * @since Java 1.1
     */
    public static final String PATH_SEPARATOR = getSystemProperty( "path.separator" );

    /**
     * <p>
     * The <code>user.country</code> or <code>user.region</code> System
     * Property. User's country code, such as <code>GB</code>. First in JDK
     * version 1.2 as <code>user.region</code>. Renamed to
     * <code>user.country</code> in 1.4
     * </p>
     * <p>
     * Defaults to <code>null</code> if the runtime does not have security
     * access to read this property or the property does not exist.
     * </p>
     * <p>
     * This value is initialized when the class is loaded. If
     * {@link System#setProperty(String,String)} or
     * {@link System#setProperties(java.util.Properties)} is called after this
     * class is loaded, the value will be out of sync with that System property.
     * </p>
     * 
     * @since 2.0
     * @since Java 1.2
     */
    public static final String USER_COUNTRY = ( getSystemProperty( "user.country" ) == null ? getSystemProperty( "user.region" )
        : getSystemProperty( "user.country" ) );

    /**
     * <p>
     * The <code>user.dir</code> System Property. User's current working
     * directory.
     * </p>
     * <p>
     * Defaults to <code>null</code> if the runtime does not have security
     * access to read this property or the property does not exist.
     * </p>
     * <p>
     * This value is initialized when the class is loaded. If
     * {@link System#setProperty(String,String)} or
     * {@link System#setProperties(java.util.Properties)} is called after this
     * class is loaded, the value will be out of sync with that System property.
     * </p>
     * 
     * @since Java 1.1
     */
    public static final String USER_DIR = getSystemProperty( USER_DIR_KEY );

    /**
     * <p>
     * The <code>user.home</code> System Property. User's home directory.
     * </p>
     * <p>
     * Defaults to <code>null</code> if the runtime does not have security
     * access to read this property or the property does not exist.
     * </p>
     * <p>
     * This value is initialized when the class is loaded. If
     * {@link System#setProperty(String,String)} or
     * {@link System#setProperties(java.util.Properties)} is called after this
     * class is loaded, the value will be out of sync with that System property.
     * </p>
     * 
     * @since Java 1.1
     */
    public static final String USER_HOME = getSystemProperty( USER_HOME_KEY );

    /**
     * <p>
     * The <code>user.language</code> System Property. User's language code,
     * such as <code>"en"</code>.
     * </p>
     * <p>
     * Defaults to <code>null</code> if the runtime does not have security
     * access to read this property or the property does not exist.
     * </p>
     * <p>
     * This value is initialized when the class is loaded. If
     * {@link System#setProperty(String,String)} or
     * {@link System#setProperties(java.util.Properties)} is called after this
     * class is loaded, the value will be out of sync with that System property.
     * </p>
     * 
     * @since 2.0
     * @since Java 1.2
     */
    public static final String USER_LANGUAGE = getSystemProperty( "user.language" );

    /**
     * <p>
     * The <code>user.name</code> System Property. User's account name.
     * </p>
     * <p>
     * Defaults to <code>null</code> if the runtime does not have security
     * access to read this property or the property does not exist.
     * </p>
     * <p>
     * This value is initialized when the class is loaded. If
     * {@link System#setProperty(String,String)} or
     * {@link System#setProperties(java.util.Properties)} is called after this
     * class is loaded, the value will be out of sync with that System property.
     * </p>
     * 
     * @since Java 1.1
     */
    public static final String USER_NAME = getSystemProperty( "user.name" );

    /**
     * <p>
     * The <code>user.timezone</code> System Property. For example:
     * <code>"America/Los_Angeles"</code>.
     * </p>
     * <p>
     * Defaults to <code>null</code> if the runtime does not have security
     * access to read this property or the property does not exist.
     * </p>
     * <p>
     * This value is initialized when the class is loaded. If
     * {@link System#setProperty(String,String)} or
     * {@link System#setProperties(java.util.Properties)} is called after this
     * class is loaded, the value will be out of sync with that System property.
     * </p>
     * 
     * @since 2.1
     */
    public static final String USER_TIMEZONE = getSystemProperty( "user.timezone" );

    // Java version
    // -----------------------------------------------------------------------
    // These MUST be declared after those above as they depend on the
    // values being set up

    /**
     * <p>
     * Gets the Java version as a <code>float</code>.
     * </p>
     * <p>
     * Example return values:
     * </p>
     * <ul>
     * <li><code>1.2f</code> for JDK 1.2
     * <li><code>1.31f</code> for JDK 1.3.1
     * </ul>
     * <p>
     * The field will return zero if {@link #JAVA_VERSION} is <code>null</code>.
     * </p>
     * 
     * @since 2.0
     */
    public static final float JAVA_VERSION_FLOAT = getJavaVersionAsFloat();

    /**
     * <p>
     * Gets the Java version as an <code>int</code>.
     * </p>
     * <p>
     * Example return values:
     * </p>
     * <ul>
     * <li><code>120</code> for JDK 1.2
     * <li><code>131</code> for JDK 1.3.1
     * </ul>
     * <p>
     * The field will return zero if {@link #JAVA_VERSION} is <code>null</code>.
     * </p>
     * 
     * @since 2.0
     */
    public static final int JAVA_VERSION_INT = getJavaVersionAsInt();

    // Java version checks
    // -----------------------------------------------------------------------
    // These MUST be declared after those above as they depend on the
    // values being set up

    /**
     * <p>
     * Is <code>true</code> if this is Java version 1.1 (also 1.1.x versions).
     * </p>
     * <p>
     * The field will return <code>false</code> if {@link #JAVA_VERSION} is
     * <code>null</code>.
     * </p>
     */
    public static final boolean IS_JAVA_1_1 = getJavaVersionMatches( "1.1" );

    /**
     * <p>
     * Is <code>true</code> if this is Java version 1.2 (also 1.2.x versions).
     * </p>
     * <p>
     * The field will return <code>false</code> if {@link #JAVA_VERSION} is
     * <code>null</code>.
     * </p>
     */
    public static final boolean IS_JAVA_1_2 = getJavaVersionMatches( "1.2" );

    /**
     * <p>
     * Is <code>true</code> if this is Java version 1.3 (also 1.3.x versions).
     * </p>
     * <p>
     * The field will return <code>false</code> if {@link #JAVA_VERSION} is
     * <code>null</code>.
     * </p>
     */
    public static final boolean IS_JAVA_1_3 = getJavaVersionMatches( "1.3" );

    /**
     * <p>
     * Is <code>true</code> if this is Java version 1.4 (also 1.4.x versions).
     * </p>
     * <p>
     * The field will return <code>false</code> if {@link #JAVA_VERSION} is
     * <code>null</code>.
     * </p>
     */
    public static final boolean IS_JAVA_1_4 = getJavaVersionMatches( "1.4" );

    /**
     * <p>
     * Is <code>true</code> if this is Java version 1.5 (also 1.5.x versions).
     * </p>
     * <p>
     * The field will return <code>false</code> if {@link #JAVA_VERSION} is
     * <code>null</code>.
     * </p>
     */
    public static final boolean IS_JAVA_1_5 = getJavaVersionMatches( "1.5" );

    // Operating system checks
    // -----------------------------------------------------------------------
    // These MUST be declared after those above as they depend on the
    // values being set up
    // OS names from http://www.vamphq.com/os.html
    // Selected ones included - please advise commons-dev@jakarta.apache.org
    // if you want another added or a mistake corrected

    /**
     * <p>
     * Is <code>true</code> if this is AIX.
     * </p>
     * <p>
     * The field will return <code>false</code> if <code>OS_NAME</code> is
     * <code>null</code>.
     * </p>
     * 
     * @since 2.0
     */
    public static final boolean IS_OS_AIX = getOSMatches( "AIX" );

    /**
     * <p>
     * Is <code>true</code> if this is HP-UX.
     * </p>
     * <p>
     * The field will return <code>false</code> if <code>OS_NAME</code> is
     * <code>null</code>.
     * </p>
     * 
     * @since 2.0
     */
    public static final boolean IS_OS_HP_UX = getOSMatches( "HP-UX" );

    /**
     * <p>
     * Is <code>true</code> if this is Irix.
     * </p>
     * <p>
     * The field will return <code>false</code> if <code>OS_NAME</code> is
     * <code>null</code>.
     * </p>
     * 
     * @since 2.0
     */
    public static final boolean IS_OS_IRIX = getOSMatches( "Irix" );

    /**
     * <p>
     * Is <code>true</code> if this is Linux.
     * </p>
     * <p>
     * The field will return <code>false</code> if <code>OS_NAME</code> is
     * <code>null</code>.
     * </p>
     * 
     * @since 2.0
     */
    public static final boolean IS_OS_LINUX = getOSMatches( "Linux" ) || getOSMatches( "LINUX" );

    /**
     * <p>
     * Is <code>true</code> if this is Mac.
     * </p>
     * <p>
     * The field will return <code>false</code> if <code>OS_NAME</code> is
     * <code>null</code>.
     * </p>
     * 
     * @since 2.0
     */
    public static final boolean IS_OS_MAC = getOSMatches( "Mac" );

    /**
     * <p>
     * Is <code>true</code> if this is Mac.
     * </p>
     * <p>
     * The field will return <code>false</code> if <code>OS_NAME</code> is
     * <code>null</code>.
     * </p>
     * 
     * @since 2.0
     */
    public static final boolean IS_OS_MAC_OSX = getOSMatches( "Mac OS X" );

    /**
     * <p>
     * Is <code>true</code> if this is OS/2.
     * </p>
     * <p>
     * The field will return <code>false</code> if <code>OS_NAME</code> is
     * <code>null</code>.
     * </p>
     * 
     * @since 2.0
     */
    public static final boolean IS_OS_OS2 = getOSMatches( "OS/2" );

    /**
     * <p>
     * Is <code>true</code> if this is Solaris.
     * </p>
     * <p>
     * The field will return <code>false</code> if <code>OS_NAME</code> is
     * <code>null</code>.
     * </p>
     * 
     * @since 2.0
     */
    public static final boolean IS_OS_SOLARIS = getOSMatches( "Solaris" );

    /**
     * <p>
     * Is <code>true</code> if this is SunOS.
     * </p>
     * <p>
     * The field will return <code>false</code> if <code>OS_NAME</code> is
     * <code>null</code>.
     * </p>
     * 
     * @since 2.0
     */
    public static final boolean IS_OS_SUN_OS = getOSMatches( "SunOS" );

    /**
     * <p>
     * Is <code>true</code> if this is a POSIX compilant system, as in any of
     * AIX, HP-UX, Irix, Linux, MacOSX, Solaris or SUN OS.
     * </p>
     * <p>
     * The field will return <code>false</code> if <code>OS_NAME</code> is
     * <code>null</code>.
     * </p>
     * 
     * @since 2.1
     */
    public static final boolean IS_OS_UNIX = IS_OS_AIX || IS_OS_HP_UX || IS_OS_IRIX || IS_OS_LINUX || IS_OS_MAC_OSX
        || IS_OS_SOLARIS || IS_OS_SUN_OS;

    /**
     * <p>
     * Is <code>true</code> if this is Windows.
     * </p>
     * <p>
     * The field will return <code>false</code> if <code>OS_NAME</code> is
     * <code>null</code>.
     * </p>
     * 
     * @since 2.0
     */
    public static final boolean IS_OS_WINDOWS = getOSMatches( OS_NAME_WINDOWS_PREFIX );

    /**
     * <p>
     * Is <code>true</code> if this is Windows 2000.
     * </p>
     * <p>
     * The field will return <code>false</code> if <code>OS_NAME</code> is
     * <code>null</code>.
     * </p>
     * 
     * @since 2.0
     */
    public static final boolean IS_OS_WINDOWS_2000 = getOSMatches( OS_NAME_WINDOWS_PREFIX, "5.0" );

    /**
     * <p>
     * Is <code>true</code> if this is Windows 95.
     * </p>
     * <p>
     * The field will return <code>false</code> if <code>OS_NAME</code> is
     * <code>null</code>.
     * </p>
     * 
     * @since 2.0
     */
    public static final boolean IS_OS_WINDOWS_95 = getOSMatches( OS_NAME_WINDOWS_PREFIX + " 9", "4.0" );

    // JDK 1.2 running on Windows98 returns 'Windows 95', hence the above

    /**
     * <p>
     * Is <code>true</code> if this is Windows 98.
     * </p>
     * <p>
     * The field will return <code>false</code> if <code>OS_NAME</code> is
     * <code>null</code>.
     * </p>
     * 
     * @since 2.0
     */
    public static final boolean IS_OS_WINDOWS_98 = getOSMatches( OS_NAME_WINDOWS_PREFIX + " 9", "4.1" );

    // JDK 1.2 running on Windows98 returns 'Windows 95', hence the above

    /**
     * <p>
     * Is <code>true</code> if this is Windows ME.
     * </p>
     * <p>
     * The field will return <code>false</code> if <code>OS_NAME</code> is
     * <code>null</code>.
     * </p>
     * 
     * @since 2.0
     */
    public static final boolean IS_OS_WINDOWS_ME = getOSMatches( OS_NAME_WINDOWS_PREFIX, "4.9" );

    // JDK 1.2 running on WindowsME may return 'Windows 95', hence the above

    /**
     * <p>
     * Is <code>true</code> if this is Windows NT.
     * </p>
     * <p>
     * The field will return <code>false</code> if <code>OS_NAME</code> is
     * <code>null</code>.
     * </p>
     * 
     * @since 2.0
     */
    public static final boolean IS_OS_WINDOWS_NT = getOSMatches( OS_NAME_WINDOWS_PREFIX + " NT" );

    // Windows 2000 returns 'Windows 2000' but may suffer from same JDK1.2
    // problem

    /**
     * <p>
     * Is <code>true</code> if this is Windows XP.
     * </p>
     * <p>
     * The field will return <code>false</code> if <code>OS_NAME</code> is
     * <code>null</code>.
     * </p>
     * 
     * @since 2.0
     */
    public static final boolean IS_OS_WINDOWS_XP = getOSMatches( OS_NAME_WINDOWS_PREFIX, "5.1" );


    // -----------------------------------------------------------------------
    /**
     * <p>
     * SystemUtils instances should NOT be constructed in standard programming.
     * Instead, the class should be used as
     * <code>SystemUtils.FILE_SEPARATOR</code>.
     * </p>
     * <p>
     * This constructor is public to permit tools that require a JavaBean
     * instance to operate.
     * </p>
     */
    public SystemUtils()
    {
        // no init.
    }


    // -----------------------------------------------------------------------
    /**
     * <p>
     * Gets the Java version number as a <code>float</code>.
     * </p>
     * <p>
     * Example return values:
     * </p>
     * <ul>
     * <li><code>1.2f</code> for JDK 1.2
     * <li><code>1.31f</code> for JDK 1.3.1
     * </ul>
     * 
     * @return the version, for example 1.31f for JDK 1.3.1
     * @deprecated Use {@link #JAVA_VERSION_FLOAT} instead. Method will be
     *             removed in Commons Lang 3.0.
     */
    public static float getJavaVersion()
    {
        return JAVA_VERSION_FLOAT;
    }


    /**
     * <p>
     * Gets the Java version number as a <code>float</code>.
     * </p>
     * <p>
     * Example return values:
     * </p>
     * <ul>
     * <li><code>1.2f</code> for JDK 1.2
     * <li><code>1.31f</code> for JDK 1.3.1
     * </ul>
     * <p>
     * Patch releases are not reported. Zero is returned if
     * {@link #JAVA_VERSION} is <code>null</code>.
     * </p>
     * 
     * @return the version, for example 1.31f for JDK 1.3.1
     */
    private static float getJavaVersionAsFloat()
    {
        if ( JAVA_VERSION == null )
        {
            return 0f;
        }
        String str = JAVA_VERSION.substring( 0, 3 );
        if ( JAVA_VERSION.length() >= 5 )
        {
            str = str + JAVA_VERSION.substring( 4, 5 );
        }
        return Float.parseFloat( str );
    }


    /**
     * <p>
     * Gets the Java version number as an <code>int</code>.
     * </p>
     * <p>
     * Example return values:
     * </p>
     * <ul>
     * <li><code>120</code> for JDK 1.2
     * <li><code>131</code> for JDK 1.3.1
     * </ul>
     * <p>
     * Patch releases are not reported. Zero is returned if
     * {@link #JAVA_VERSION} is <code>null</code>.
     * </p>
     * 
     * @return the version, for example 131 for JDK 1.3.1
     */
    private static int getJavaVersionAsInt()
    {
        if ( JAVA_VERSION == null )
        {
            return 0;
        }
        String str = JAVA_VERSION.substring( 0, 1 );
        str = str + JAVA_VERSION.substring( 2, 3 );
        if ( JAVA_VERSION.length() >= 5 )
        {
            str = str + JAVA_VERSION.substring( 4, 5 );
        }
        else
        {
            str = str + "0";
        }
        return Integer.parseInt( str );
    }


    /**
     * <p>
     * Decides if the java version matches.
     * </p>
     * 
     * @param versionPrefix
     *            the prefix for the java version
     * @return true if matches, or false if not or can't determine
     */
    private static boolean getJavaVersionMatches( String versionPrefix )
    {
        if ( JAVA_VERSION == null )
        {
            return false;
        }
        return JAVA_VERSION.startsWith( versionPrefix );
    }


    /**
     * <p>
     * Decides if the operating system matches.
     * </p>
     * 
     * @param osNamePrefix
     *            the prefix for the os name
     * @return true if matches, or false if not or can't determine
     */
    private static boolean getOSMatches( String osNamePrefix )
    {
        if ( OS_NAME == null )
        {
            return false;
        }
        return OS_NAME.startsWith( osNamePrefix );
    }


    /**
     * <p>
     * Decides if the operating system matches.
     * </p>
     * 
     * @param osNamePrefix
     *            the prefix for the os name
     * @param osVersionPrefix
     *            the prefix for the version
     * @return true if matches, or false if not or can't determine
     */
    private static boolean getOSMatches( String osNamePrefix, String osVersionPrefix )
    {
        if ( OS_NAME == null || OS_VERSION == null )
        {
            return false;
        }
        return OS_NAME.startsWith( osNamePrefix ) && OS_VERSION.startsWith( osVersionPrefix );
    }


    // -----------------------------------------------------------------------
    /**
     * <p>
     * Gets a System property, defaulting to <code>null</code> if the property
     * cannot be read.
     * </p>
     * <p>
     * If a <code>SecurityException</code> is caught, the return value is
     * <code>null</code> and a message is written to <code>System.err</code>.
     * </p>
     * 
     * @param property
     *            the system property name
     * @return the system property value or <code>null</code> if a security
     *         problem occurs
     */
    private static String getSystemProperty( String property )
    {
        try
        {
            return System.getProperty( property );
        }
        catch ( SecurityException ex )
        {
            // we are not allowed to look at this property
            System.err.println( I18n.err( I18n.ERR_04437, property ) );
            return null;
        }
    }


    /**
     * <p>
     * Is the Java version at least the requested version.
     * </p>
     * <p>
     * Example input:
     * </p>
     * <ul>
     * <li><code>1.2f</code> to test for JDK 1.2</li>
     * <li><code>1.31f</code> to test for JDK 1.3.1</li>
     * </ul>
     * 
     * @param requiredVersion
     *            the required version, for example 1.31f
     * @return <code>true</code> if the actual version is equal or greater
     *         than the required version
     */
    public static boolean isJavaVersionAtLeast( float requiredVersion )
    {
        return ( JAVA_VERSION_FLOAT >= requiredVersion );
    }


    /**
     * <p>
     * Is the Java version at least the requested version.
     * </p>
     * <p>
     * Example input:
     * </p>
     * <ul>
     * <li><code>120</code> to test for JDK 1.2 or greater</li>
     * <li><code>131</code> to test for JDK 1.3.1 or greater</li>
     * </ul>
     * 
     * @param requiredVersion
     *            the required version, for example 131
     * @return <code>true</code> if the actual version is equal or greater
     *         than the required version
     * @since 2.0
     */
    public static boolean isJavaVersionAtLeast( int requiredVersion )
    {
        return ( JAVA_VERSION_INT >= requiredVersion );
    }


    /**
     * Returns whether the {@link #JAVA_AWT_HEADLESS} value is <code>true</code>.
     * 
     * @return <code>true</code> if <code>JAVA_AWT_HEADLESS</code> is
     *         <code>"true"</code>, <code>false</code> otherwise.
     * @see #JAVA_AWT_HEADLESS
     * @since 2.1
     * @since Java 1.4
     */
    public static boolean isJavaAwtHeadless()
    {
        return JAVA_AWT_HEADLESS != null ? JAVA_AWT_HEADLESS.equals( Boolean.TRUE.toString() ) : false;
    }


    /**
     * <p>
     * Gets the Java home directory as a <code>File</code>.
     * </p>
     * 
     * @return a directory
     * @throws SecurityException
     *             if a security manager exists and its
     *             <code>checkPropertyAccess</code> method doesn't allow
     *             access to the specified system property.
     * @see System#getProperty(String)
     */
    public static File getJavaHome()
    {
        return new File( System.getProperty( JAVA_HOME_KEY ) );
    }


    /**
     * <p>
     * Gets the Java IO temporary directory as a <code>File</code>.
     * </p>
     * 
     * @return a directory
     * @throws SecurityException
     *             if a security manager exists and its
     *             <code>checkPropertyAccess</code> method doesn't allow
     *             access to the specified system property.
     * @see System#getProperty(String)
     */
    public static File getJavaIoTmpDir()
    {
        return new File( System.getProperty( JAVA_IO_TMPDIR_KEY ) );
    }


    /**
     * <p>
     * Gets the user directory as a <code>File</code>.
     * </p>
     * 
     * @return a directory
     * @throws SecurityException
     *             if a security manager exists and its
     *             <code>checkPropertyAccess</code> method doesn't allow
     *             access to the specified system property.
     * @see System#getProperty(String)
     */
    public static File getUserDir()
    {
        return new File( System.getProperty( USER_DIR_KEY ) );
    }


    /**
     * <p>
     * Gets the user home directory as a <code>File</code>.
     * </p>
     * 
     * @return a directory
     * @throws SecurityException
     *             if a security manager exists and its
     *             <code>checkPropertyAccess</code> method doesn't allow
     *             access to the specified system property.
     * @see System#getProperty(String)
     */
    public static File getUserHome()
    {
        return new File( System.getProperty( USER_HOME_KEY ) );
    }

}