/**
 * This application demonstrates how to synchronize multiple threads
 * @author hornick
 */
package two_method_sync;

/**
 * Main class; creates a secondary thread upon creation
 */
public class ThreadSyncDemoApp {

	private Object signal = new Object(); // a generic Object (any Object-derived object can be used) used for synchronization

	/**
	 * standard main method; just creates an instance of this application object
	 * @param args - not used
	 */
	public static void main(String[] args) {
		new ThreadSyncDemoApp();

	}

	/**
	 * Default ctor.
	 * Creates a secondary thread which executes a method.
	 * Ctor then executes another method on the main thread.
	 */
	public ThreadSyncDemoApp() {
		Thread t = new Thread(							// create a secondary Thread
				new Runnable() {			// create an object that can be run by the Thread (must implement Runnable) 
					public void run() {		// implement a run() method (makes the object a Runnable)
						outputUppercaseMessage("secondary thread");			// the run() method just calls one of this application's methods
					}
				}
		);
		t.start();							// start the Thread, which causes the method above to execute off the main thread

		outputLowercaseMessage("main thread");
		System.out.println("Main thread done.");
	}

	/**
	 * Outputs the given String to the console, in uppercase only.
	 * @param msg the String to output to the console
	 */
	public void outputUppercaseMessage( String msg ) {
		pause(500);
		while(true) {	// output forever
			synchronized( signal ) {	// only one thread at a time can enter this block, the signal guards the entrance
				for( int c=0; c<msg.length(); c++ ) {  // output the message in uppercase, one char at a time
					System.out.print(msg.toUpperCase().charAt(c));
					pause(10);
				}
				System.out.println();
				signal.notify();		// notify any waiting thread that the this thread is releasing its signal
				try {
					signal.wait();		// wait for another thread to notify this thread to proceed
				} catch( InterruptedException e ) {
					System.out.println("Interrupted outputUppercaseMessage.");
				}
			}
		}		
	}
	/**
	 * Outputs the given String to the console, in lowercase only.
	 * @param msg the String to output to the console
	 */
	public void outputLowercaseMessage( String msg ) {
		for(int i=0; i<10; i++ ) {	// output 10 times
			synchronized( signal ) {	// only one thread at a time can enter this block, the signal guards the entrance
				for( int c=0; c<msg.length(); c++ ) {  // output the message in uppercase, one char at a time
					System.out.print(msg.toLowerCase().charAt(c));
					pause(10);
				}
				System.out.println();				
				signal.notify();		// notify any waiting thread that the this thread is releasing its signal
				try {
					signal.wait();		// wait for another thread to notify this thread to proceed
				} catch( InterruptedException e ) {
					System.out.println("Interrupted outputLowercaseMessage.");
				}
			}
		}		
	}

	
	/**
	 * sleep for the specified number of milliseconds
	 * @param t - amount of time to sleep (in ms)
	 */
	private void pause( long t ) {
		try {
			Thread.sleep(t);
		} catch( InterruptedException e ) {
			// do nothing
		}
	}
}