簡單生產消費者模型

import java.util.ArrayList;
import java.util.List;

public class ProduceAndConsume {
	public static final Object signal = new Object();
	public static List<String> list = new ArrayList<String>();
	public static void main(String args[]) {
		Thread produce = new Thread(new Produce());
		Thread consume = new Thread(new Consume());
		produce.start();
		consume.start();
	}
}

class Produce implements Runnable{
	@Override
	public void run() {
		int sequence = 0;
		while(true) {
			synchronized(ProduceAndConsume.signal){
				for (int i = 0; i < 3; i++) {
					ProduceAndConsume.list.add(sequence + "commodity");
				}
				sequence++;
				try {
					ProduceAndConsume.signal.notify();
					ProduceAndConsume.signal.wait();
				} catch (InterruptedException e) {
					e.printStackTrace();
				}
			}
		}
	}
	
}
class Consume implements Runnable{
	@Override
	public void run() {
		int count = 0;
		while(count < 5) {
			synchronized(ProduceAndConsume.signal) { 
				try {
					ProduceAndConsume.signal.wait();
				} catch (InterruptedException e) {
					e.printStackTrace();
				}
				if(ProduceAndConsume.list.size() > 0) {
					for (String str : ProduceAndConsume.list) {
						System.out.println(str);
					}
					ProduceAndConsume.list.clear();
					count++;
					ProduceAndConsume.signal.notify();
				}
			}
		}
	}
}

注意

1.消費和生產必定要用同一把鎖ProduceAndConsume.signal
2.ProduceAndConsume.signal.wait()的做用是當前線程暫停，釋放鎖signal，轉到等待隊列中，等待signal這個信號量（signal也是鎖）的通知。等到signal的通知以後（而不能是其餘信號量的通知），這個線程纔有機會轉到就緒隊列中，去競爭執行的機會。
3.ProduceAndConsume.signal.notify()的做用是通知等待在signal這個信號量的單個線程從等待隊列中進入就緒隊列，準備競爭執行的機會。但調用ProduceAndConsume.signal.notify()方法的線程並不會立刻釋放鎖，而是把代碼執行完後再釋放鎖，由於notify只是通知其餘等待在這個信號量的線程進入就緒隊列，準備競爭鎖。