| /* |
| * 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.Serializable; |
| |
| |
| /** |
| * <p> |
| * Operations on <code>Object</code>. |
| * </p> |
| * <p> |
| * This class tries to handle <code>null</code> input gracefully. An exception |
| * will generally not be thrown for a <code>null</code> input. Each method |
| * documents its behaviour in more detail. |
| * </p> |
| * |
| * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a> |
| */ |
| public class ObjectUtils |
| { |
| |
| /** |
| * <p> |
| * Singleton used as a <code>null</code> placeholder where |
| * <code>null</code> has another meaning. |
| * </p> |
| * <p> |
| * For example, in a <code>HashMap</code> the |
| * {@link java.util.HashMap#get(java.lang.Object)} method returns |
| * <code>null</code> if the <code>Map</code> contains <code>null</code> |
| * or if there is no matching key. The <code>Null</code> placeholder can |
| * be used to distinguish between these two cases. |
| * </p> |
| * <p> |
| * Another example is <code>Hashtable</code>, where <code>null</code> |
| * cannot be stored. |
| * </p> |
| * <p> |
| * This instance is Serializable. |
| * </p> |
| */ |
| public static final Null NULL = new Null(); |
| |
| |
| /** |
| * <p> |
| * <code>ObjectUtils</code> instances should NOT be constructed in |
| * standard programming. Instead, the class should be used as |
| * <code>ObjectUtils.defaultIfNull("a","b");</code>. |
| * </p> |
| * <p> |
| * This constructor is public to permit tools that require a JavaBean |
| * instance to operate. |
| * </p> |
| */ |
| public ObjectUtils() |
| { |
| } |
| |
| |
| // Defaulting |
| // ----------------------------------------------------------------------- |
| /** |
| * <p> |
| * Returns a default value if the object passed is <code>null</code>. |
| * </p> |
| * |
| * <pre> |
| * ObjectUtils.defaultIfNull(null, null) = null |
| * ObjectUtils.defaultIfNull(null, "") = "" |
| * ObjectUtils.defaultIfNull(null, "zz") = "zz" |
| * ObjectUtils.defaultIfNull("abc", *) = "abc" |
| * ObjectUtils.defaultIfNull(Boolean.TRUE, *) = Boolean.TRUE |
| * </pre> |
| * |
| * @param object |
| * the <code>Object</code> to test, may be <code>null</code> |
| * @param defaultValue |
| * the default value to return, may be <code>null</code> |
| * @return <code>object</code> if it is not <code>null</code>, |
| * defaultValue otherwise |
| */ |
| public static Object defaultIfNull( Object object, Object defaultValue ) |
| { |
| return ( object != null ? object : defaultValue ); |
| } |
| |
| |
| /** |
| * <p> |
| * Compares two objects for equality, where either one or both objects may |
| * be <code>null</code>. |
| * </p> |
| * |
| * <pre> |
| * ObjectUtils.equals(null, null) = true |
| * ObjectUtils.equals(null, "") = false |
| * ObjectUtils.equals("", null) = false |
| * ObjectUtils.equals("", "") = true |
| * ObjectUtils.equals(Boolean.TRUE, null) = false |
| * ObjectUtils.equals(Boolean.TRUE, "true") = false |
| * ObjectUtils.equals(Boolean.TRUE, Boolean.TRUE) = true |
| * ObjectUtils.equals(Boolean.TRUE, Boolean.FALSE) = false |
| * </pre> |
| * |
| * @param object1 |
| * the first object, may be <code>null</code> |
| * @param object2 |
| * the second object, may be <code>null</code> |
| * @return <code>true</code> if the values of both objects are the same |
| */ |
| public static boolean equals( Object object1, Object object2 ) |
| { |
| if ( object1 == object2 ) |
| { |
| return true; |
| } |
| if ( ( object1 == null ) || ( object2 == null ) ) |
| { |
| return false; |
| } |
| return object1.equals( object2 ); |
| } |
| |
| |
| /** |
| * <p> |
| * Gets the hash code of an object returning zero when the object is |
| * <code>null</code>. |
| * </p> |
| * |
| * <pre> |
| * ObjectUtils.hashCode(null) = 0 |
| * ObjectUtils.hashCode(obj) = obj.hashCode() |
| * </pre> |
| * |
| * @param obj |
| * the object to obtain the hash code of, may be |
| * <code>null</code> |
| * @return the hash code of the object, or zero if null |
| * @since 2.1 |
| */ |
| public static int hashCode( Object obj ) |
| { |
| return ( ( obj == null ) ? 0 : obj.hashCode() ); |
| } |
| |
| |
| // Identity ToString |
| // ----------------------------------------------------------------------- |
| /** |
| * <p> |
| * Gets the toString that would be produced by <code>Object</code> if a |
| * class did not override toString itself. <code>null</code> will return |
| * <code>null</code>. |
| * </p> |
| * |
| * <pre> |
| * ObjectUtils.identityToString(null) = null |
| * ObjectUtils.identityToString("") = "java.lang.String@1e23" |
| * ObjectUtils.identityToString(Boolean.TRUE) = "java.lang.Boolean@7fa" |
| * </pre> |
| * |
| * @param object |
| * the object to create a toString for, may be <code>null</code> |
| * @return the default toString text, or <code>null</code> if |
| * <code>null</code> passed in |
| */ |
| public static String identityToString( Object object ) |
| { |
| if ( object == null ) |
| { |
| return null; |
| } |
| return appendIdentityToString( null, object ).toString(); |
| } |
| |
| |
| /** |
| * <p> |
| * Appends the toString that would be produced by <code>Object</code> if a |
| * class did not override toString itself. <code>null</code> will return |
| * <code>null</code>. |
| * </p> |
| * |
| * <pre> |
| * ObjectUtils.appendIdentityToString(*, null) = null |
| * ObjectUtils.appendIdentityToString(null, "") = "java.lang.String@1e23" |
| * ObjectUtils.appendIdentityToString(null, Boolean.TRUE) = "java.lang.Boolean@7fa" |
| * ObjectUtils.appendIdentityToString(buf, Boolean.TRUE) = buf.append("java.lang.Boolean@7fa") |
| * </pre> |
| * |
| * @param buffer |
| * the buffer to append to, may be <code>null</code> |
| * @param object |
| * the object to create a toString for, may be <code>null</code> |
| * @return the default toString text, or <code>null</code> if |
| * <code>null</code> passed in |
| * @since 2.0 |
| */ |
| public static StringBuffer appendIdentityToString( StringBuffer buffer, Object object ) |
| { |
| if ( object == null ) |
| { |
| return null; |
| } |
| if ( buffer == null ) |
| { |
| buffer = new StringBuffer(); |
| } |
| return buffer.append( object.getClass().getName() ).append( '@' ).append( |
| Integer.toHexString( System.identityHashCode( object ) ) ); |
| } |
| |
| |
| // ToString |
| // ----------------------------------------------------------------------- |
| /** |
| * <p> |
| * Gets the <code>toString</code> of an <code>Object</code> returning an |
| * empty string ("") if <code>null</code> input. |
| * </p> |
| * |
| * <pre> |
| * ObjectUtils.toString(null) = "" |
| * ObjectUtils.toString("") = "" |
| * ObjectUtils.toString("bat") = "bat" |
| * ObjectUtils.toString(Boolean.TRUE) = "true" |
| * </pre> |
| * |
| * @see String#valueOf(Object) |
| * @param obj |
| * the Object to <code>toString</code>, may be null |
| * @return the passed in Object's toString, or nullStr if <code>null</code> |
| * input |
| * @since 2.0 |
| */ |
| public static String toString( Object obj ) |
| { |
| return ( obj == null ? "" : obj.toString() ); |
| } |
| |
| |
| /** |
| * <p> |
| * Gets the <code>toString</code> of an <code>Object</code> returning a |
| * specified text if <code>null</code> input. |
| * </p> |
| * |
| * <pre> |
| * ObjectUtils.toString(null, null) = null |
| * ObjectUtils.toString(null, "null") = "null" |
| * ObjectUtils.toString("", "null") = "" |
| * ObjectUtils.toString("bat", "null") = "bat" |
| * ObjectUtils.toString(Boolean.TRUE, "null") = "true" |
| * </pre> |
| * |
| * @see String#valueOf(Object) |
| * @param obj |
| * the Object to <code>toString</code>, may be null |
| * @param nullStr |
| * the String to return if <code>null</code> input, may be null |
| * @return the passed in Object's toString, or nullStr if <code>null</code> |
| * input |
| * @since 2.0 |
| */ |
| public static String toString( Object obj, String nullStr ) |
| { |
| return ( obj == null ? nullStr : obj.toString() ); |
| } |
| |
| // Null |
| // ----------------------------------------------------------------------- |
| /** |
| * <p> |
| * Class used as a null placeholder where <code>null</code> has another |
| * meaning. |
| * </p> |
| * <p> |
| * For example, in a <code>HashMap</code> the |
| * {@link java.util.HashMap#get(java.lang.Object)} method returns |
| * <code>null</code> if the <code>Map</code> contains <code>null</code> |
| * or if there is no matching key. The <code>Null</code> placeholder can |
| * be used to distinguish between these two cases. |
| * </p> |
| * <p> |
| * Another example is <code>Hashtable</code>, where <code>null</code> |
| * cannot be stored. |
| * </p> |
| */ |
| public static class Null implements Serializable |
| { |
| // declare serialization compatibility with Commons Lang 1.0 |
| private static final long serialVersionUID = 7092611880189329093L; |
| |
| |
| /** |
| * Restricted constructor - singleton. |
| */ |
| Null() |
| { |
| } |
| |
| |
| /** |
| * <p> |
| * Ensure singleton. |
| * </p> |
| * |
| * @return the singleton value |
| */ |
| private Object readResolve() |
| { |
| return ObjectUtils.NULL; |
| } |
| } |
| |
| } |
