Java Crash捕捉

JVM为我们提供了线程的未捕获异常处理机制，通过Thread的setUncaughtExceptionHandler(UncaughtExceptionHandler)方法

public void setUncaughtExceptionHandler(UncaughtExceptionHandler eh)

也可以通过静态方法setDefaultUncaughtExceptionHandler(UncaughtExceptionHandler)

public static void setDefaultUncaughtExceptionHandler(UncaughtExceptionHandler eh)

CrashCaught类，可以设置未捕捉异常处理机制，并发出未处理异常

public class CrashCaught extends Thread {
    private boolean caught;

    public CrashCaught(boolean caught) {
        this.caught = caught;
    }

    @Override
    public void run() {
        System.out.println(getName());

        if (caught) {
            setUncaughtExceptionHandler(new MyUncaughtExceptionHandler());
        }

        try {
            Thread.sleep(2000);
        } catch (InterruptedException e) {
        }

        throw new NullPointerException();
    }

}

MyUncaughtExceptionHandler类捕捉未处理异常

static class MyUncaughtExceptionHandler implements UncaughtExceptionHandler {
    String name;
	
    public MyUncaughtExceptionHandler() {
        this.name = Thread.currentThread().getName();
    }

    @Override
    public void uncaughtException(Thread t, Throwable e) {
        System.out.println("In Handler " + name);
        System.out.println("Thread name " + t.getName());
        e.printStackTrace();
    }
}

main()方法设置默认UncaughtExceptionHandler

public static void main(String[] args) {
    Thread.setDefaultUncaughtExceptionHandler(new MyUncaughtExceptionHandler());

    new CrashCaught(false).start();
    
    try {
        Thread.sleep(3000);
    } catch (InterruptedException e) {
    }

    new CrashCaught(true).start();
}

如果设置了setDefaultUncaughtExceptionHandler()，会捕捉所有未处理异常，除非该线程已经设置了setUncaughtExceptionHandler()