package main.java.multithreads; public class ThreeThreads { public static int a = 0; public static void main(String[] args) { // thread A new Thread(new Runnable() { @Override public void run() { while (a < 20) { a ++; } } }).start(); // thread B new Thread(new Runnable() { @Override public void run() { while (a < 100) { a *= 10; } } }).start(); // thread C new Thread(new Runnable() { @Override public void run() { while (a > 0) { a --; } } }).start(); System.out.println(a); } } 0-200或死循环 理论上来说System.out.println(a);可以在任何时候输出, 虽然实际运行起来0 或200 或死循环的情况比较多.