package concurrent;

import java.util.*;
import java.util.concurrent.atomic.*;

public class AtomicIntegerLimit {
	
	private AtomicInteger ai = new AtomicInteger(1);
	private int limit;
	
	public AtomicIntegerLimit(int limit) {
		this.limit = limit;
	}
	
	public int getInt() {
	    for (;;) {
	      int i = ai.get();
	      int j = i + 1;
	      if (i == limit)
	    	  j = 1;
	      if (ai.compareAndSet(i, j)) {
	        return i;
	      }
	    }
	}
	
	public static void main(String[] args) throws Exception {
		int limit = 20;
		int threadCnt = 10;
		final int loopCnt = 1000;
		final AtomicIntegerLimit ait = new AtomicIntegerLimit(limit);
		final ArrayList<Integer> intList = new ArrayList<Integer>();
		ArrayList<Thread> threadList = new ArrayList<Thread>();
		
		for (int tidx = 0; tidx < threadCnt; ++tidx) {
			Thread thread = new Thread() {
				public void run() {
					for (int idx = 0; idx < loopCnt; ++idx) {
						int va = ait.getInt();
						synchronized (intList) {
							intList.add(va);
						}
					}
				}
			};
			thread.start();
			threadList.add(thread);
		}
		for (Thread thread: threadList)
			thread.join();
		for (int idx = 1; idx <= limit; ++idx) {
			int cnt = 0;
			for (Integer integer: intList) {
				if (idx == integer)
					++cnt;
			}
			System.out.println("" + idx + ":" + cnt);
		}
	}
}