当前位置：首页 > news >正文

JAVA EE初阶 2：多线程-初阶

news 2025/11/15 15:50:21

1.认识线程（Thread）

1.1 概念

1.2 创建线程(lambda最常用)

1.2.1 方法1 - 继承Thread类

【 Ctrl + C 取消终止】

1.2.2 方法2 - 实现Runnable接口

1.2.3 总结

1.2.4 匿名内部类

2.Thread类及常见方法

2.1 构造方法

2.2 常见属性

2.3 启动一个线程 start()

调用start方法，才真的在操作系统的底层创建出⼀个线程。

2.4 中断一个线程

package thread;public class Demo7 {private static boolean flag = true;public static void main(String[] args) throws InterruptedException {Thread t = new Thread(() -> {   while(flag){System.out.println("hello thread");try {Thread.sleep(1000);} catch (InterruptedException e) {// TODO Auto-generated catch blocke.printStackTrace();}}});t.start();System.out.println("hello main");Thread.sleep(3000);flag = false;System.out.println("让 t 线程终止");}}

package thread;public class Demo7 {public static void main(String[] args) throws InterruptedException {Thread t = new Thread(() -> {   while(Thread.currentThread().isInterrupted()){System.out.println("hello thread");try {Thread.sleep(1000);} catch (InterruptedException e) {// TODO Auto-generated catch blocke.printStackTrace();}}});t.start();System.out.println("hello main");Thread.sleep(3000);t.interrupt();System.out.println("t 线程的中断标志位：" + t.isInterrupted());}}

2.5 等待一个线程 join()

有时，我们需要等待一个线程完成它的工作后，才能进的下⼀步工作，这时我们需要⼀个方法明确等待线程的结束。

主线程等待代码

package thread;public class Demo7 {public static void main(String[] args) throws InterruptedException {Thread t = new Thread(() -> {for(int i = 0; i < 5; i++){System.out.println("hello thread");try {Thread.sleep(1000);} catch (InterruptedException e) {// TODO Auto-generated catch block//e.printStackTrace();break;}}});System.out.println("主线程开始");t.start();System.out.println("主线程等待之前");t.join();System.out.println("主线程等待之后");System.out.println("主线程结束");}
}

t 线程等待代码

package thread;public class Demo7 {public static void main(String[] args) throws InterruptedException {Thread mainThread = Thread.currentThread();Thread t = new Thread(() -> {try {System.out.println("t 线程等待之前");mainThread.join();System.out.println("t 线程等待之后");} catch (InterruptedException e) {// TODO Auto-generated catch blocke.printStackTrace();}});t.start();for(int i = 0; i < 3; i++){System.out.println("hello main");Thread.sleep(1000);}}
}

2.6 获取当前线程引用

2.7 休眠当前线程

3.线程的状态

线程的状态是⼀个枚举类型 Thread.State

4.多线程带来的的风险-线程安全(重点！)

4.1 概念例子

4.2 线程不安全的原因

5.死锁（重点）

    Object lock1 = new Object();Object lock2 = new Object();Thread t1 = new Thread() {@Overridepublic void run() {synchronized (lock1) {synchronized (lock2) {// do something...}}}};t1.start();Thread t2 = new Thread() {@Overridepublic void run() {synchronized (lock2) {synchronized (lock1) {// do something...}}}};t2.start();

不会产生环路等待的代码:约定好先获取lock1,再获取lock2,就不会环路等待。

    Object lock1 = new Object();Object lock2 = new Object();Thread t1 = new Thread() {@Overridepublic void run() {synchronized (lock1) {synchronized (lock2) {// do something...}}}};t1.start();Thread t2 = new Thread() {@Overridepublic void run() {synchronized (lock1) {synchronized (lock2) {// do something...}}}};t2.start();