Java 简明教程
Java - Creating a Thread
在 Java 中有两种创建线程的不同方法。我们已将其列出如下:
There are two different ways to create a thread in Java. We have listed them as follows:
-
By Implementing a Runnable Interface
-
By Extending a Thread Class
Create a Thread by Implementing a Runnable Interface
如果准备将您的类作为线程执行,那么可以通过实现 Runnable 接口实现此目的。您需要遵循三个基本步骤 −
If your class is intended to be executed as a thread then you can achieve this by implementing a Runnable interface. You will need to follow three basic steps −
Step 1
第一步,您需要实现 Runnable 接口提供的 run() 方法。此方法为线程提供了一个入口点,您需要将完整业务逻辑放入此方法内。以下是 run() 方法的一个简单语法:
As a first step, you need to implement a run() method provided by a Runnable interface. This method provides an entry point for the thread and you will put your complete business logic inside this method. Following is a simple syntax of the run() method −
public void run( )
Step 2
作为第二步,您将使用以下构造函数实例化一个 Thread 对象 −
As a second step, you will instantiate a Thread object using the following constructor −
Thread(Runnable threadObj, String threadName);
其中,threadObj 是实现 Runnable 接口的类的实例,threadName 是赋予新线程的名称。
Where, threadObj is an instance of a class that implements the Runnable interface and threadName is the name given to the new thread.
Step 3
创建 Thread 对象后,可通过调用 start() method 来启动它,它会执行调用 run( ) 方法。以下是 start() 方法的简单语法:
Once a Thread object is created, you can start it by calling start() method, which executes a call to run( ) method. Following is a simple syntax of start() method −
void start();
Example to Create a Thread by Implementing a Runnable Interface
在本示例中,我们通过实现 Runnable 接口来创建一个类 RunnableDemo。RunnableDemo 类具有 run() 方法实现。在 main 类 TestThread 中,我们创建了 RunnableDemo 对象,并且使用这些对象我们创建了两个 Thread 对象。在每个线程对象上调用 Thread.start() 方法时,线程开始处理并且执行程序。
In this example, we’re creating a class RunnableDemo by implementing Runnable interface. RunnableDemo class has run() method implementation. In main class TestThread, we’ve created the RunnableDemo objects and using those objects we’ve created two Thread objects. When Thread.start() method is called on each thread objects, threads start processing and program is executed.
package com.tutorialspoint;
class RunnableDemo implements Runnable {
private String threadName;
RunnableDemo( String name) {
threadName = name;
System.out.println("Thread: " + threadName + ", " + "State: New");
}
public void run() {
System.out.println("Thread: " + threadName + ", " + "State: Running");
for(int i = 4; i > 0; i--) {
System.out.println("Thread: " + threadName + ", " + i);
}
System.out.println("Thread: " + threadName + ", " + "State: Dead");
}
}
public class TestThread {
public static void main(String args[]) {
RunnableDemo runnableDemo1 = new RunnableDemo( "Thread-1");
RunnableDemo runnableDemo2 = new RunnableDemo( "Thread-2");
Thread thread1 = new Thread(runnableDemo1);
Thread thread2 = new Thread(runnableDemo2);
thread1.start();
thread2.start();
}
}
Thread: Thread-1, State: New
Thread: Thread-2, State: New
Thread: Thread-1, State: Running
Thread: Thread-1, 4
Thread: Thread-1, 3
Thread: Thread-1, 2
Thread: Thread-1, 1
Thread: Thread-1, State: Dead
Thread: Thread-2, State: Running
Thread: Thread-2, 4
Thread: Thread-2, 3
Thread: Thread-2, 2
Thread: Thread-2, 1
Thread: Thread-2, State: Dead
Create a Thread by Extending a Thread Class
创建线程的第二种方法是,使用以下两个简单步骤,创建一个扩展 Thread 类的类。这种方法提供了更多灵活性,可使用 Thread class 中的可用方法来处理创建的多个线程。
The second way to create a thread is to create a new class that extends Thread class using the following two simple steps. This approach provides more flexibility in handling multiple threads created using available methods in Thread class.
Step 1
您需要覆盖 Thread 类中可用的 run() method 。此方法为线程提供了一个入口点,您需要将您的完整业务逻辑放入此方法中。以下是 run() 方法的简单语法:
You will need to override run() method available in Thread class. This method provides an entry point for the thread and you will put your complete business logic inside this method. Following is a simple syntax of run() method −
public void run( )
Step 2
一旦创建 Thread 对象,便可以通过调用 start() 方法来启动它,该调用会执行一个 run( ) 方法调用。以下是 start() 方法的一个简单语法 −
Once Thread object is created, you can start it by calling start() method, which executes a call to run( ) method. Following is a simple syntax of start() method −
void start( );
Example to Create a Thread by Extending a Thread Class
下面是对继承 Thread 的程序的重写 - 在本示例中,我们创建了一个扩展 Thread 类的 ThreadDemo 类。我们在 constructor() 方法中调用 super(name) 为线程分配一个名称,并且调用 super.start() 来启动线程处理。
Here is the preceding program rewritten to extend the Thread − In this example, we’ve created a ThreadDemo class which extends Thread class. We’re calling super(name) in constructor() method to assign a name to the thread and called super.start() to start the thread processing.
package com.tutorialspoint;
class ThreadDemo extends Thread {
ThreadDemo( String name) {
super(name);
System.out.println("Thread: " + name + ", " + "State: New");
}
public void run() {
System.out.println("Thread: " + Thread.currentThread().getName() + ", " + "State: Running");
for(int i = 4; i > 0; i--) {
System.out.println("Thread: " + Thread.currentThread().getName() + ", " + i);
}
System.out.println("Thread: " + Thread.currentThread().getName() + ", " + "State: Dead");
}
public void start () {
System.out.println("Thread: " + Thread.currentThread().getName() + ", " + "State: Start");
super.start();
}
}
public class TestThread {
public static void main(String args[]) {
ThreadDemo thread1 = new ThreadDemo( "Thread-1");
ThreadDemo thread2 = new ThreadDemo( "Thread-2");
thread1.start();
thread2.start();
}
}
Thread: Thread-1, State: New
Thread: Thread-2, State: New
Thread: main, State: Start
Thread: main, State: Start
Thread: Thread-1, State: Running
Thread: Thread-1, 4
Thread: Thread-1, 3
Thread: Thread-1, 2
Thread: Thread-2, State: Running
Thread: Thread-1, 1
Thread: Thread-1, State: Dead
Thread: Thread-2, 4
Thread: Thread-2, 3
Thread: Thread-2, 2
Thread: Thread-2, 1
Thread: Thread-2, State: Dead
Example: Demonstrating sleep() Method
在此示例中,我们展示了使用 sleep() method 来延迟处理。它有助于在输出中显示并行处理。我们在 run 方法中添加了 Thread.sleep() 调用。InterruptedException 被处理,因为线程在睡眠模式期间可能被中断。
In this example, we’re show-casing use of sleep() method to delay the processing. It helps in show the parallel processing in the output. We’ve added Thread.sleep() call in the run method. InterruptedException is handled as thread can be interrupted during sleep mode.
package com.tutorialspoint;
class ThreadDemo extends Thread {
ThreadDemo( String name) {
super(name);
System.out.println("Thread: " + name + ", " + "State: New");
}
public void run() {
System.out.println("Thread: " + Thread.currentThread().getName() + ", " + "State: Running");
for(int i = 4; i > 0; i--) {
System.out.println("Thread: " + Thread.currentThread().getName() + ", " + i);
try {
Thread.sleep(50);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
System.out.println("Thread: " + Thread.currentThread().getName() + ", " + "State: Dead");
}
public void start () {
System.out.println("Thread: " + Thread.currentThread().getName() + ", " + "State: Start");
super.start();
}
}
public class TestThread {
public static void main(String args[]) {
ThreadDemo thread1 = new ThreadDemo( "Thread-1");
ThreadDemo thread2 = new ThreadDemo( "Thread-2");
thread1.start();
thread2.start();
}
}
Thread: Thread-1, State: New
Thread: Thread-2, State: New
Thread: main, State: Start
Thread: main, State: Start
Thread: Thread-1, State: Running
Thread: Thread-1, 4
Thread: Thread-2, State: Running
Thread: Thread-2, 4
Thread: Thread-2, 3
Thread: Thread-1, 3
Thread: Thread-1, 2
Thread: Thread-2, 2
Thread: Thread-2, 1
Thread: Thread-1, 1
Thread: Thread-1, State: Dead
Thread: Thread-2, State: Dead