/*

 * Copyright (c) 2015, 2020, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

package com.sun.org.apache.xml.internal.utils;

import java.util.concurrent.atomic.AtomicInteger;

/**

 * Represents a safe thread that does not inherit thread-locals and runs only

 * once.

 */

public class SafeThread extends Thread {

    private volatile boolean ran = false;

    private static final AtomicInteger threadNumber = new AtomicInteger(1);

    private static String threadName() {

        return "SafeThread-" + threadNumber.getAndIncrement();

    }

    public SafeThread(Runnable target) {

        this(null, target, threadName());

    }

    public SafeThread(Runnable target, String name) {

        this(null, target, name);

    }

    public SafeThread(ThreadGroup group, Runnable target, String name) {

        super(group, target, name, 0, false);

    }

    public final void run() {

        if (Thread.currentThread() != this) {

            throw new IllegalStateException("The run() method in a"

                    + " SafeThread cannot be called from another thread.");

        }

        synchronized (this) {

            if (!ran) {

                ran = true;

            } else {

                throw new IllegalStateException("The run() method in a"

                        + " SafeThread cannot be called more than once.");

            }

        }

        super.run();

    }

}