Java异常处理UncaughtExceptionHandler使用实例代码详解

2023-03-01 11:03:05 异常 实例 详解

异常处理

线程未捕获异常 UncaughtException 需要UncaughtZExceptionHandler 来进行处理

那么为什么非要用UncaughtZExceptionHandler呢？

  • 主线程可以轻松捕获线程，子线程不可以
  • 从下面代码可知，即使子线程抛出异常，主线程丝毫不受影响
public class ChildException implements Runnable{
    public static void main(String[] args) {
        new Thread(new ChildException()).start();
        for (int i = 0; i < 10; i++) {
            System.out.println(i);
        }
    }
    @Override
    public void run() {
        throw new RuntimeException();
    }
}
  • 从下面代码可知，即使想用catch捕获子线程异常，时没有用的
  • try catch 是针对主线程的，没有办法捕获子线程的异常
public class CantCatch implements Runnable {
    public static void main(String[] args) throws InterruptedException {
        try {
            new Thread(new CantCatch(), "thread0").start();
            Thread.sleep(300);
            new Thread(new CantCatch(), "thread1").start();
            Thread.sleep(300);
            new Thread(new CantCatch(), "thread2").start();
            Thread.sleep(300);
            new Thread(new CantCatch(), "thread3").start();
            Thread.sleep(300);
        } catch (RuntimeException e) {
            System.out.println("catch");
        }
    }
    @Override
    public void run() {
        throw new RuntimeException();
    }
}

在run方法中进行try catch可以捕获到异常，但是特别麻烦，因为需要手动地在每个run方法中都进行try catch

UncaughtExceptionHandler

自定义UncaughtExceptionHandler

public class MyUncaughtHandler implements Thread.UncaughtExceptionHandler{
    private String name;
    public MyUncaughtHandler(String name) {
        this.name = name;
    }
    @Override
    public void uncaughtException(Thread t, Throwable e) {
        Logger logger = Logger.getAnonymousLogger();
        logger.log(Level.WARNING, "线程异常" + t.getName(), e);
        System.out.println(name + "捕获" + t.getName()+ e);
    }
}

使用自定义的类来捕获异常

public class UseOwnExceptionHandler implements Runnable {
    public static void main(String[] args) throws InterruptedException {
        Thread.setDefaultUncaughtExceptionHandler(new MyUncaughtHandler("MyHandler"));
//        try {
        new Thread(new UseOwnExceptionHandler(), "thread0").start();
        Thread.sleep(300);
        new Thread(new UseOwnExceptionHandler(), "thread1").start();
        Thread.sleep(300);
        new Thread(new UseOwnExceptionHandler(), "thread2").start();
        Thread.sleep(300);
        new Thread(new UseOwnExceptionHandler(), "thread3").start();
        Thread.sleep(300);
//        } catch (RuntimeException e) {
//            System.out.println("catch");
//        }
    }
    @Override
    public void run() {
//        try {
        throw new RuntimeException();
//        } catch (RuntimeException e) {
//            System.out.println("e");
//        }
    }
}

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