Try,Catch和Finally块

Question

public class D {

void myMethod() {
    try {
        throw new IllegalArgumentException();
    } catch (NullPointerException npex) {
        System.out.println("NullPointerException thrown ");
    } catch (Exception ex) {
        System.out.println("Exception thrown ");
    } finally {
        System.out.println("Done with exceptions ");
    }
    System.out.println("myMethod is done");
}

public static void main(String args[]) {
    D d = new D();
    d.myMethod();
}

}

我不明白怎么"myMethod is done"也被打印出来.抛出了异常,因此它假设找到一个匹配的catch并执行finally块,但它继续在该myMethod方法上打印myMethod is done,而不是finally块的一部分.为什么？

Answer 1

这就是try-catch-finally的工作方式.因为您捕获了异常,所以它被认为已被处理,并且执行继续正常进行.

如果你没有抓住它,或者重新抛出它,那么"myMethod就完成了"就不会被打印出来,并且异常会在堆栈中冒出来,直到它被别人抓到.

请注意,finally块始终执行,异常或否.

Answer 2

另一方面,如果您有以下内容:

void myMethod() {
    try {
        throw new IllegalArgumentException();

        System.out.println("Line after exception");   /// new line added here

    } catch (NullPointerException npex) {
        System.out.println("NullPointerException thrown ");
    } catch (Exception ex) {
        System.out.println("Exception thrown ");
    } finally {
        System.out.println("Done with exceptions ");
    }
    System.out.println("myMethod is done");
}

public static void main(String args[]) {
    D d = new D();
    d.myMethod();
}

然后"异常后线"将不打印.