Using multithreading to output abc10 times in sequence

Multithreading is a common technology in both interview and company . Today, I passed a small topic, integrating multiple multithreading technologies .
This problem is the use of multi-threaded continuous output ABC Ten times . First , Let me first explain that the solution to this problem is not the only way , And I only offer one , Other methods are expected to be tried by readers themselves . The first step is to define three threads , Inherit Runnablej Interface , Rewrite the method and add synchronized lock ,（synchronized Is a mutually exclusive synchronous lock , The function is to run only one thread at a time in a multithreaded program , And synchronize changes ）, Only synchronized Not enough , We need to volatile Keyword modifies a variable used to control the execution order of threads （volatile It can ensure the visibility and order between threads , But there's no guarantee of atomicity , Therefore, thread safety can only be guaranteed under appropriate scenarios ）. adopt java Medium wait（） Method （ Use wait（） Method needs to be started notify() Method to restart the thread ） Control thread interval .

public class ThreadABC {
    
	private volatile static int flag = 1;

	public static void main(String[] args) throws IOException, InterruptedException{
    
		
		Thread threada = new Thread(new Runnable() {
    
			
			@Override
			public synchronized void run() {
    
				try {
    
					while(flag!=1) {
    
						wait();
					}
					System.out.println("A");
					flag = 2;
					notify();
				}catch (Exception e) {
    
					e.printStackTrace();
				}
				
			}
		});
		Thread threadb = new Thread(new Runnable() {
    
			
			@Override
			public synchronized void run() {
    
				try {
    
					while(flag!=2) {
    
						wait();
					}
					System.out.println("B");
					flag =3;
					notify();
				}catch (Exception e) {
    
					e.printStackTrace();
				}
				
			}
		});
		Thread threadc = new Thread(new Runnable() {
    
			
			@Override
			public synchronized void run() {
    
				try {
    
					while(flag !=3) {
    
						wait();
					}
					System.out.println("C");
					flag = 1;
					notify();
				}catch (Exception e) {
    
					e.printStackTrace();
				}
				
			}
		});
		ExecutorService pool = Executors.newCachedThreadPool();
		for(int i = 0;i<10;i++) {
    
			pool.execute(threada);
			pool.execute(threadb);
			pool.execute(threadc);
			
		}
	}

}