004_Scheduler.java

// Coding Interviews: Questions, Analysis & Solutions
// Harry He


public class Scheduler {
    public class SimpleThread extends Thread{
        private int value;
        public SimpleThread(int num) {
            this.value = num;
            
            start();
        }
        
        public void run(){
            while(true) {
                synchronized(this){
                    try {
                        wait();
                    } catch (InterruptedException e) {
                        throw new RuntimeException(e);
                    }
                    
                    System.out.print(value + " ");
                }
            }
        }
    }
    
    static final int COUNT = 3;
    static final int SLEEP = 37;

    public static void main(String args[]) {
        Scheduler scheduler = new Scheduler();
        SimpleThread threads[] = new SimpleThread[COUNT];
        for(int i = 0; i < COUNT; ++i)
            threads[i] = scheduler.new SimpleThread(i + 1);
        
        int index = 0;
        while(true){
            synchronized(threads[index]) {
                threads[index].notify();
            }
            
            try {
                Thread.sleep(SLEEP);
            } catch (InterruptedException e) {
                throw new RuntimeException(e);
            }
            
            index = (++index) % COUNT;
        }
    }
}