/**
 * CountThread
 * first Thread class
 * problem of multiple threads updating a shared resource
 */

// (1) extends Thread
public class CountThread extends Thread {
    private static final int GOAL_EVEN = 20;
    private static final int GOAL_ODD  =  0;
    
    // shared resource
    private static int shared = 10;
    
    // inidividual resource
    private int id;
    
    public CountThread(int id) {
        this.id = id;
    }
    
    // (2) override run()
    // override the behavior of the threads
    @Override
    public void run() {
        
        if (id % 2 == 0) { // even threads: increment shared
            while (shared < GOAL_EVEN) {
                ++shared;
                System.out.printf("id: %d shared=%d\n", id, shared);
            }
            
        }
        else { // odd threads: decrement shared
            while (shared > GOAL_ODD) {
                --shared;
                System.out.printf("id: %d shared=%d\n", id, shared);
            }
        }
        
    }
    
    public static void main(String[] args) {
        CountThread ct1 = new CountThread(1);
        CountThread ct2 = new CountThread(2);
        
        // (3) have the threads start working
        ct1.start();
        ct2.start();
        
        // (4) wait until all threads are done
        try {
            ct1.join();
            ct2.join();
        }
        catch(InterruptedException e) {
            System.err.println("Threads interrupted");
            e.printStackTrace();
        }
        
        System.out.println("main process: Done");
        
    }

}