在 Java 中实现 Runnable 接口与扩展线程
java programming java 8object oriented programming
我们可以通过实现 Runnable 接口或扩展 Thread 类来创建线程。以下是这两种创建线程方式的详细步骤。
通过实现 Runnable 接口创建线程
如果您的类需要以线程形式执行，那么您可以通过实现 Runnable 接口来实现。您需要遵循三个基本步骤 −
步骤 1
首先，您需要实现 Runnable 接口提供的 run() 方法。此方法为线程提供了入口点，您可以将完整的业务逻辑放入此方法中。以下是 run() 方法的简单语法 −
public void run( )
步骤 2
第二步，您将使用以下构造函数 −
实例化一个 Thread 对象Thread(Runnable threadObj, String threadName);
其中，threadObj 是实现 Runnable 接口的类的实例，threadName 是新线程的名称。
步骤 3
创建 Thread 对象后，您可以通过调用 start() 方法来启动它，该方法会执行对 run( ) 方法的调用。以下是 start() 方法的简单语法 −
void start();
示例
这是一个创建新线程并开始运行的示例 −
class RunnableDemo implements Runnable {
private Thread t;
private String threadName;
RunnableDemo( String name) {
threadName = name;
System.out.println("Creating " + threadName );
}
public void run() {
System.out.println("Running " + threadName );
try {
for(int i = 4; i > 0; i--) {
System.out.println("Thread: " + threadName + ", " + i);
// Let the thread sleep for a while.
Thread.sleep(50);
}
} catch (InterruptedException e) {
System.out.println("Thread " + threadName + " interrupted.");
}
System.out.println("Thread " + threadName + " exiting.");
}
public void start () {
System.out.println("Starting " + threadName );
if (t == null) {
t = new Thread (this, threadName);
t.start ();
}
}
}
public class TestThread {
public static void main(String args[]) {
RunnableDemo R1 = new RunnableDemo( "Thread-1");
R1.start();
RunnableDemo R2 = new RunnableDemo( "Thread-2");
R2.start();
}
}
这将产生以下结果 −
输出
Creating Thread-1 Starting Thread-1 Creating Thread-2 Starting Thread-2 Running Thread-1 Thread: Thread-1, 4 Running Thread-2 Thread: Thread-2, 4 Thread: Thread-1, 3 Thread: Thread-2, 3 Thread: Thread-1, 2 Thread: Thread-2, 2 Thread: Thread-1, 1 Thread: Thread-2, 1 Thread Thread-1 exiting. Thread Thread-2 exiting.
通过扩展 Thread 类创建线程
创建线程的第二种方法是创建一个扩展 Thread 类的新类，只需执行以下两个简单步骤。这种方法在处理使用 Thread 类中可用方法创建的多线程时提供了更大的灵活性。
步骤 1
您需要重写 Thread 类中的 run() 方法。此方法为线程提供了入口点，您可以将完整的业务逻辑放入此方法中。以下是 run() 方法的简单语法 −
public void run( )
步骤 2
创建 Thread 对象后，您可以通过调用 start() 方法来启动它，该方法会执行对 run() 方法的调用。以下是 start() 方法的简单语法 −
void start( );
示例
Here is the preceding program rewritten to extend the Thread −
class ThreadDemo extends Thread {
private Thread t;
private String threadName;
ThreadDemo( String name) {
threadName = name;
System.out.println("Creating " + threadName );
}
public void run() {
System.out.println("Running " + threadName );
try {
for(int i = 4; i > 0; i--) {
System.out.println("Thread: " + threadName + ", " + i);
// 让线程休眠一会儿。
Thread.sleep(50);
}
} catch (InterruptedException e) {
System.out.println("Thread " + threadName + " interrupted.");
}
System.out.println("Thread " + threadName + " exiting.");
}
public void start () {
System.out.println("Starting " + threadName );
if (t == null) {
t = new Thread (this, threadName);
t.start ();
}
}
}
public class TestThread {
public static void main(String args[]) {
ThreadDemo T1 = new ThreadDemo( "Thread-1");
T1.start();
ThreadDemo T2 = new ThreadDemo( "Thread-2");
T2.start();
}
}
这将产生以下结果 −
输出
Creating Thread-1 Starting Thread-1 Creating Thread-2 Starting Thread-2 Running Thread-1 Thread: Thread-1, 4 Running Thread-2 Thread: Thread-2, 4 Thread: Thread-1, 3 Thread: Thread-2, 3 Thread: Thread-1, 2 Thread: Thread-2, 2 Thread: Thread-1, 1 Thread: Thread-2, 1 Thread Thread-1 exiting. Thread Thread-2 exiting.
