Java中的多线程如何实现线程通信

package com.ietree.multithread.sync;import java.util.ArrayList;import java.util.List;public class MyList {    private volatile static List list = new ArrayList();  public void add() {    list.add("apple");  }  public int size() {    return list.size();  }  public static void main(String[] args) {    final MyList list1 = new MyList();    Thread t1 = new Thread(new Runnable() {      @Override      public void run() {        try {          for (int i = 0; i < 10; i++) {            list1.add();            System.out.println("当前线程：" + Thread.currentThread().getName() + "添加了一个元素..");            Thread.sleep(500);          }        } catch (InterruptedException e) {          e.printStackTrace();        }      }    }, "t1");    Thread t2 = new Thread(new Runnable() {      @Override      public void run() {        while (true) {          if (list1.size() == 5) {            System.out.println("当前线程收到通知：" + Thread.currentThread().getName() + " list size = 5 线程停止..");            throw new RuntimeException();          }        }      }    }, "t2");    t1.start();    t2.start();  }}