如何在 Java 中获取当前运行线程的 Id？
线程类的 getId() 方法返回被调用线程的标识符。线程标识是创建该线程时生成的长正数。线程标识是唯一的，并且在其生存期内保持不变。当一个线程被终止时，这个线程标识可以被重用。
Java 允许在线程的帮助下并行执行程序的不同部分。Java 中的多线程是通过扩展线程类或实现可运行接口来实现的。由于 Java 中不允许多重继承，所以建议实现 Runnable 接口来创建线程，这样如果需要，实现 Runnable 接口的类可以扩展一些其他类。在本文中，我们已经演示了创建线程的两种方法。第一种方法通过扩展 thread 类显示线程创建，第二种方法通过实现 Runnable Interface 显示线程创建。
申报T0】
返回值: 这个方法返回一个线程的 ID。
方法 1: 以下是通过扩展线程类来创建线程的步骤。
- The ThreadDemo1 class extends the Thread class and covers the run () method of the Thread class.
- In the run () method, we use currentthread (). The method gets the name of the current thread that called the run () method.
- We use currentthread (). Getid () method gets the Id of the current thread that called the run () method.
- In the main () method, two instances of the ThreadDemo1 class are created.
- T1 and t2 are two threads that call the start () method.
- Calling the start () method basically calls the run () method by default.
- join () method is used to prevent T2 from running before t1 is completed.
- As soon as t1 completes T2, it will be executed.
示例:
Java
// Java program to get the id of a
// thread
import java.util.*;
public class ThreadDemo1 extends Thread {
public void run()
{
// gets the name of current thread
System.out.println(
"Current Thread Name: "
+ Thread.currentThread().getName());
// gets the ID of the current thread
System.out.println(
"Current Thread ID: "
+ Thread.currentThread().getId());
}
public static void main(String[] args)
throws InterruptedException
{
Scanner s = new Scanner(System.in);
// creating first thread
ThreadDemo1 t1 = new ThreadDemo1();
// creating second thread
ThreadDemo1 t2 = new ThreadDemo1();
// Starting the thread
t1.start();
t2.start();
// t2 does not start execution until t1 completes
// execution
t1.join();
}
}
输出
Current Thread Name: Thread-0
Current Thread Name: Thread-1
Current Thread ID: 11
Current Thread ID: 12
方法 2: 在第二种方法中，通过实现可运行接口来创建线程。
- The ThreadDemo2 class implements the Runnable interface and overrides the run () method.
- A runnable instance of thread demo class 2 T is created.
- Two instances of the Thread class are created by passing the runnable instance as the first parameter and the thread name as the second parameter.
- The start () method is called on two threads.
- The start () method calls the run () method by default.
示例:
Java
// Java program to get the id of a
// thread
public class ThreadDemo2 implements Runnable {
public void run()
{
// gets the name of current thread
System.out.println(
"Current Thread Name: "
+ Thread.currentThread().getName());
// gets the ID of the current thread
System.out.println(
"Current Thread ID: "
+ Thread.currentThread().getId());
}
public static void main(String[] args)
{
// Runnable target
ThreadDemo2 t = new ThreadDemo2();
// create threads
Thread t1 = new Thread(t, "First Thread");
Thread t2 = new Thread(t, "Second Thread");
// start threads
t1.start();
t2.start();
}
}
输出
Current Thread Name: First Thread
Current Thread Name: Second Thread
Current Thread ID: 11
Current Thread ID: 12
注意:第二种方法的输出可能会有所不同，因为它不是同步的，并且线程是并发执行的。因此，线程名称或线程 id 的打印顺序可能会有所不同。为了防止这个问题，我们在第一种方法中使用了 join() 方法。如果要保持打印输出的顺序，那么用户可以使用 join()方法。
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