1

考虑以下带有方法的类：a() 调用 b()，而 b() 又调用 c()。

public class ReThrower {

    public static void a(int a1){
        try{
           a1+=1;
           b(a1);
        }
        catch(ArithmeticException e){
            System.out.println("Exception caught at a");
            throw e;
        }
    }

    public static void b(int b1){
        try{
            b1+=1;
            c(b1);
        }
        catch(ArithmeticException e){
            System.out.println("Exception caught at b");
            throw e;
        }

    }

    public static void c(int c1){
        int zero=0,result;
        try{
            result=c1/zero;
        }
        catch(ArithmeticException e){
            System.out.println("Exception caught at c");
            e.printStackTrace();
            throw e;
        }

    }

    public static void main(String[] args) {
        a(5);
    }

}

当我运行上面的代码时，收到的初始输出是：

Exception caught at c
java.lang.ArithmeticException: / by zero
Exception caught at b
Exception caught at a
    at com.atul.security.ReThrower.c(ReThrower.java:31)
    at com.atul.security.ReThrower.b(ReThrower.java:20)
    at com.atul.security.ReThrower.a(ReThrower.java:10)
    at com.atul.security.ReThrower.main(ReThrower.java:46)
Exception in thread "main" java.lang.ArithmeticException: / by zero
    at com.atul.security.ReThrower.c(ReThrower.java:31)
    at com.atul.security.ReThrower.b(ReThrower.java:20)
    at com.atul.security.ReThrower.a(ReThrower.java:10)
    at com.atul.security.ReThrower.main(ReThrower.java:46)

甚至在 c() 打印完整的堆栈跟踪之前，b() 和 a() 中包含的 sysout 就已经被执行了。但是，当我再次运行它时，输出改变如下：

    Exception caught at c
Exception caught at b
Exception caught at a
java.lang.ArithmeticException: / by zero
    at com.atul.security.ReThrower.c(ReThrower.java:31)
    at com.atul.security.ReThrower.b(ReThrower.java:20)
    at com.atul.security.ReThrower.a(ReThrower.java:10)
    at com.atul.security.ReThrower.main(ReThrower.java:46)
Exception in thread "main" java.lang.ArithmeticException: / by zero
    at com.atul.security.ReThrower.c(ReThrower.java:31)
    at com.atul.security.ReThrower.b(ReThrower.java:20)
    at com.atul.security.ReThrower.a(ReThrower.java:10)
    at com.atul.security.ReThrower.main(ReThrower.java:46)

鉴于这是单线程的，为什么在多次运行中行为会发生变化？

4

1 回答 1

3

e.printStacktrace打印到，System.err而您用 . 打印其余行System.out。当您打印到两个流时，结果可能看起来乱七八糟。

于 2013-06-18T11:19:56.107 回答