在finally和catch块中抛出异常

Question

对catch中抛出的异常有问题,最后阻止:

class MyExc1 extends Exception {}
class MyExc2 extends Exception {}
class MyExc3 extends MyExc2 {}

public class C1 {
    public static void main(String[] args) throws Exception {
        try {
            System.out.print(1);
            q();
        }
        catch (Exception i) {
            throw new MyExc2();
        }
        finally {
            System.out.print(2);
            throw new MyExc1();
        }
    }
    static void q() throws Exception {
        try {
            throw new MyExc1();
        }
        catch (Exception y) {
            System.out.print(3);
        }
        finally {
            System.out.print(4);
            throw new Exception();
        }
    }

}

我试过多次执行上面的代码.它每次给我不同的输出.

output 1: 1Exception in thread "main" 342test.MyExc1
at test.C1.main(C1.java:18)
output 2: 1342Exception in thread "main" test.MyExc1
at test.C1.main(C1.java:18)
output 3: 1Exception in thread "main" test.MyExc1
342 at test.C1.main(C1.java:18)
output4:  1Exception in thread "main" 34test.MyExc1
2 at test.C1.main(C1.java:18)

请解释.

Answer 1

所有你看到的是写作System.out和之间的竞争条件System.err.您显式调用System.out.print1,然后是3,然后是4,然后是2,并且异常被抛出并System.err自动转储.所以你得到的每一个输出都是"1342",其中有异常堆栈跟踪.

实际执行流程在每种情况下都是相同的 - 它只是输出不同.为了证明这一点,你可以将整个main方法包装在写入异常的try/ catchblock System.out中,此时它将与所有现有的System.out调用同步,并且没有竞争条件.