src/java/org/apache/commons/math/MathException.java

/*
 * Copyright 2003-2004 The Apache Software Foundation.
 *
 * Licensed 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.commons.math;

import java.io.PrintStream;
import java.io.PrintWriter;


/**
* Base class for commons-math checked exceptions.
* <p>
* Supports nesting, emulating JDK 1.4 behavior if necessary.  
* <p>
* Adapted from {@link org.apache.commons.collections.FunctorException}.
* 
* @version $Revision$ $Date$
*/
public class MathException extends Exception {
    
    /** Serializable version identifier */
    static final long serialVersionUID = -8594613561393443827L;
    
    /**
     * Does JDK support nested exceptions?
     */
    private static final boolean JDK_SUPPORTS_NESTED;
    
    static {
        boolean flag = false;
        try {
            Throwable.class.getDeclaredMethod("getCause", new Class[0]);
            flag = true;
        } catch (NoSuchMethodException ex) {
            flag = false;
        }
        JDK_SUPPORTS_NESTED = flag;
    }
    
    /**
     * Root cause of the exception
     */
    private final Throwable rootCause;
    
    /**
     * Constructs a new <code>MathException</code> with no
     * detail message.
     */
    public MathException() {
        super();
        this.rootCause = null;
    }
    
    /**
     * Constructs a new <code>MathException</code> with specified
     * detail message.
     *
     * @param msg  the error message.
     */
    public MathException(String msg) {
        super(msg);
        this.rootCause = null;
    }
    
    /**
     * Constructs a new <code>MathException</code> with specified
     * nested <code>Throwable</code> root cause.
     *
     * @param rootCause  the exception or error that caused this exception
     *                   to be thrown.
     */
    public MathException(Throwable rootCause) {
        super((rootCause == null ? null : rootCause.getMessage()));
        this.rootCause = rootCause;
    }
    
    /**
     * Constructs a new <code>MathException</code> with specified
     * detail message and nested <code>Throwable</code> root cause.
     *
     * @param msg  the error message.
     * @param rootCause  the exception or error that caused this exception
     *                   to be thrown.
     */
    public MathException(String msg, Throwable rootCause) {
        super(msg);
        this.rootCause = rootCause;
    }
    
    /**
     * Gets the cause of this throwable.
     * 
     * @return  the cause of this throwable, or <code>null</code>
     */
    public Throwable getCause() {
        return rootCause;
    }
    
    /**
     * Prints the stack trace of this exception to the standard error stream.
     */
    public void printStackTrace() {
        printStackTrace(System.err);
    }
    
    /**
     * Prints the stack trace of this exception to the specified stream.
     *
     * @param out  the <code>PrintStream</code> to use for output
     */
    public void printStackTrace(PrintStream out) {
        synchronized (out) {
            PrintWriter pw = new PrintWriter(out, false);
            printStackTrace(pw);
            // Flush the PrintWriter before it's GC'ed.
            pw.flush();
        }
    }
    
    /**
     * Prints the stack trace of this exception to the specified writer.
     *
     * @param out  the <code>PrintWriter</code> to use for output
     */
    public void printStackTrace(PrintWriter out) {
        synchronized (out) {
            super.printStackTrace(out);
            if (rootCause != null && JDK_SUPPORTS_NESTED == false) {
                out.print("Caused by: ");
                rootCause.printStackTrace(out);
            }
        }
    }

}