Java开发中的并发（线程的创建和使用）

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线程状态：
图片来源

线程状态有：new, ready, running, waiting, terminated, blocked

1.使用Runnable 接口

Runnable 源码

@FunctionalInterface public interface Runnable { /**
     * When an object implementing interface <code>Runnable</code> is used
     * to create a thread, starting the thread causes the object's
     * <code>run</code> method to be called in that separately executing
     * thread.
     * <p>
     * The general contract of the method <code>run</code> is that it may
     * take any action whatsoever.
     *
     * @see     java.lang.Thread#run()
     */ public abstract void run(); } 

Runnable 接口中仅有一个run()抽象函数

通过接口Runnable 实现多线程

class Solution { public static class RunableTask implements Runnable{ @Override public void run(){ System.out.println(Thread.currentThread()); } } public static void main(String[] args) { RunableTask runableTask = new RunableTask(); new Thread(runableTask).start(); new Thread(runableTask).start(); } } 

输出结果：

可以看到，实现了Runnable 接口的类被送到了Thread()中进行启动线程

Thread类也继承了Runnable 接口，通过new Thread(runnable)，使用构造函数创建新线程。

 /**
     * Allocates a new {@code Thread} object. This constructor has the same
     * effect as {@linkplain #Thread(ThreadGroup,Runnable,String) Thread}
     * {@code (null, target, gname)}, where {@code gname} is a newly generated
     * name. Automatically generated names are of the form
     * {@code "Thread-"+}<i>n</i>, where <i>n</i> is an integer.
     *
     * @param  target
     *         the object whose {@code run} method is invoked when this thread
     *         is started. If {@code null}, this classes {@code run} method does
     *         nothing.
     */ public Thread(Runnable target) { init(null, target, "Thread-" + nextThreadNum(), 0); } /**
     * Initializes a Thread with the current AccessControlContext.
     * @see #init(ThreadGroup,Runnable,String,long,AccessControlContext,boolean)
     */ private void init(ThreadGroup g, Runnable target, String name, long stackSize) { init(g, target, name, stackSize, null, true); } /**
     * Initializes a Thread.
     *
     * @param g the Thread group
     * @param target the object whose run() method gets called
     * @param name the name of the new Thread
     * @param stackSize the desired stack size for the new thread, or
     *        zero to indicate that this parameter is to be ignored.
     * @param acc the AccessControlContext to inherit, or
     *            AccessController.getContext() if null
     * @param inheritThreadLocals if {@code true}, inherit initial values for
     *            inheritable thread-locals from the constructing thread
     */ private void init(ThreadGroup g, Runnable target, String name, long stackSize, AccessControlContext acc, boolean inheritThreadLocals) { if (name == null) { throw new NullPointerException("name cannot be null"); } this.name = name; ............... //代码过长，就不贴了 

2.继承extend类

重写Thread类的run()方法，调用Thread的start()即可启动线程

class Solution { public static class MyThread extends Thread{ @Override public void run(){ System.out.println(Thread.currentThread()); } } public static void main(String[] args) { MyThread thread = new MyThread(); thread.start(); } } 

3.FutureTask 线程返回值

创建CallerTask 任务类，将该任务传递给Thread 并启动线程，之后便可以将返回值通过get()方法获取。

class Solution { public static class CallerTask implements Callable<String>{ @Override public String call() throws Exception{ return Thread.currentThread().toString(); } } public static void main(String[] args) throws Exception { FutureTask<String> futureTask = new FutureTask<>(new CallerTask()); new Thread(futureTask).start(); String res = futureTask.get(); System.out.println(res); } } 

本文地址：https://blog.csdn.net/baidu_41560343/article/details/107884635