有时希望把刚捕获的异常重新抛出，尤其是在使用Exception捕获的异常的时候。既然已经得到了对当前异常对象的引用，可以直接把它重新抛出：
catch(Exception e){
Systyem.out.println(“An exception was thrown”);
throw e;
}
重抛异常会把异常抛给上一级环境中的异常处理程序，同一个try块的后续catch子句将被忽略。此外，异常对象的所有信息都得以保持，所以高一级环境中捕获此异常的
处理程序可以从这个异常对象中得到所有信息。
如果只是把当前异常对象重新抛出，那么printStackTrace（）方法显示的将是原来的异常的抛出点的调用堆栈信息，而并非重新抛出点的信息。要想更新这个信息，可以调用fillInStackTrace()方法，这将返回一个Throwable对象，它是通过把当前调用栈信息填入原来那个异常对象建立的，如下：
1 package com.exceptions; 2 3 4 public class Rethrowing { 5 6 public static void f() throws Exception{ 7 System.out.println("originating the exception in f()"); 8 throw new Exception("throw from f()"); 9 } 10 11 public static void g() throws Exception{ 12 try{ 13 f(); 14 }catch(Exception e){ 15 System.out.println("Inside g(), e.printStackTrace()"); 16 e.printStackTrace(System.out); 17 throw e; 18 } 19 } 20 21 public static void h() throws Exception{ 22 try{ 23 f(); 24 }catch(Exception e){ 25 System.out.println("Inside h(), e.printStackTrace()"); 26 e.printStackTrace(System.out); 27 throw (Exception)e.fillInStackTrace(); 28 } 29 } 30 public static void main(String[] args) { 31 // TODO Auto-generated method stub 32 try{ 33 g(); 34 }catch(Exception e){ 35 System.out.println("main: printStackTrace()"); 36 e.printStackTrace(System.out); 37 } 38 try{ 39 h(); 40 }catch(Exception e){ 41 System.out.println("main: printStackTrace()"); 42 e.printStackTrace(System.out); 43 } 44 } 45 46 }
结果：
1 originating the exception in f() 2 Inside g(), e.printStackTrace() 3 java.lang.Exception: throw from f() 4 at com.exceptions.Rethrowing.f(Rethrowing.java:8) 5 at com.exceptions.Rethrowing.g(Rethrowing.java:13) 6 at com.exceptions.Rethrowing.main(Rethrowing.java:33) 7 main: printStackTrace() 8 java.lang.Exception: throw from f() 9 at com.exceptions.Rethrowing.f(Rethrowing.java:8) 10 at com.exceptions.Rethrowing.g(Rethrowing.java:13) 11 at com.exceptions.Rethrowing.main(Rethrowing.java:33) 12 originating the exception in f() 13 Inside h(), e.printStackTrace() 14 java.lang.Exception: throw from f() 15 at com.exceptions.Rethrowing.f(Rethrowing.java:8) 16 at com.exceptions.Rethrowing.h(Rethrowing.java:23) 17 at com.exceptions.Rethrowing.main(Rethrowing.java:39) 18 main: printStackTrace() 19 java.lang.Exception: throw from f() 20 at com.exceptions.Rethrowing.h(Rethrowing.java:27) 21 at com.exceptions.Rethrowing.main(Rethrowing.java:39)