How to create a thread in java

Java uses the Thread class to represent threads, and all thread objects must be instances of the Thread class or its subclasses. Java can create threads in three ways, as follows:

1) Inherit the Thread class to create a thread

2) Implement the Runnable interface to create a thread

3) Use Callable Creating threads with Future

Let's take a look at these three methods of creating threads respectively.

The steps for inheriting the Thread class to create a thread are as follows:

1】D define a subclass of the Thread class and override the run() method of the class. The method body is the task that the thread needs to complete. The run() method is also called the thread execution body.

2] Create an instance of the Thread subclass, that is, create a thread object

3] Start the thread, that is, call the start() method of the thread

Example:

public class MyThread extends Thread{//继承Thread类
　　public void run(){
　　//重写run方法
　　}
}
public class Main {
　　public static void main(String[] args){
　　　　new MyThread().start();//创建并启动线程
　　}
}

The steps to implement the Runnable interface to create a thread are as follows:

1] Define the implementation class of the Runnable interface, and also override the run() method, this run() The method is the execution body of the thread like the run() method in Thread

2】Create an instance of the Runnable implementation class, and use this instance as the target of Thread to create a Thread object. This Thread object is the real thread. Object

3】The third part is still to start the thread by calling the start() method of the thread object

Example:

public class MyThread2 implements Runnable {//实现Runnable接口
　　public void run(){
　　//重写run方法
　　}
}
public class Main {
　　public static void main(String[] args){
　　　　//创建并启动线程
　　　　MyThread2 myThread=new MyThread2();
　　　　Thread thread=new Thread(myThread);
　　　　thread().start();
　　　　//或者    new Thread(new MyThread2()).start();
　　}
}

Use Callable and Future to create a thread The steps are as follows:

1] Create an implementation class of the Callable interface, implement the call() method, and then create an instance of the implementation class (starting from java8, you can directly use Lambda expressions to create Callable objects).

2] Use the FutureTask class to wrap the Callable object. The FutureTask object encapsulates the return value of the call() method of the Callable object.

3] Use the FutureTask object as the target of the Thread object to create and start it. Thread (because FutureTask implements the Runnable interface)

4】Call the get() method of the FutureTask object to obtain the return value after the execution of the child thread ends

Example:

public class Main {
　　public static void main(String[] args){
　　　MyThread3 th=new MyThread3();
　　　//使用Lambda表达式创建Callable对象
　　   //使用FutureTask类来包装Callable对象
　　　FutureTask<Integer> future=new FutureTask<Integer>(
　　　　(Callable<Integer>)()->{
　　　　　　return 5;
　　　　}
　　  );
　　　new Thread(task,"有返回值的线程").start();//实质上还是以Callable对象来创建并启动线程
　　  try{
　　　　System.out.println("子线程的返回值："+future.get());//get()方法会阻塞，直到子线程执行结束才返回
 　　 }catch(Exception e){
　　　　ex.printStackTrace();
　　　}
　　}
}

For more java knowledge, please pay attention to the java basic tutorial column.

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