MaskingThread.java

/*
 * Copyright 2011 Jesper Terkelsen.
 * 
 * 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 dk.deck.remoteconsole.input;

import java.io.PrintStream;

/**
 * This class attempts to erase characters echoed to the console.
 * @author Jesper Terkelsen
 */
class MaskingThread extends Thread {

    private volatile boolean stop;
    private char echochar = '*';
    private PrintStream out;

    /**
     * @param prompt The prompt displayed to the user
     * @param out The PrintStream to mask on (e.g. System.out)
     */
    public MaskingThread(String prompt, PrintStream out) {
        this.out = out;
        this.out.print(prompt);
    }

    /**
     * Begin masking until asked to stop.
     */
    @Override
    public void run() {

        int priority = Thread.currentThread().getPriority();
        Thread.currentThread().setPriority(Thread.MAX_PRIORITY);

        try {
            stop = true;
            while (stop) {
                out.print("\010" + echochar);
                try {
                    // attempt masking at this rate
                    Thread.currentThread().sleep(1);
                } catch (InterruptedException iex) {
                    Thread.currentThread().interrupt();
                }
            }
        } finally { // restore the original priority
            Thread.currentThread().setPriority(priority);
        }
    }

    /**
     * Instruct the thread to stop masking.
     */
    public void stopMasking() {
        this.stop = false;
    }
}