Exception 笔记

来源：互联网发布：二次解析接口源码编辑：程序博客网时间：2024/05/17 00:14

package exceptiontest.test;public class ExceptionTest1 {public static void f(){System.out.println("f()");throw new RuntimeException();}public static void main(String[] args) {System.out.println("start main");f();}}

虚拟机捕捉到异常，这个是由main方法抛出：执行过程为：运行start main,调用f方法，打印f()，在下一行抛出异常，main没有捕获，由main抛出，虚拟机捕获打印

Exception in thread "main" java.lang.RuntimeException                    //at exceptiontest.test.ExceptionTest1.f(ExceptionTest1.java:7)    //出错地点  at + 类全路径.方法名(类型名.java:行数)at exceptiontest.test.ExceptionTest1.main(ExceptionTest1.java:14)  //上一个出错地点

捕捉异常之后处理

1）打印异常，不会终止程序

package exceptiontest.test;public class ExceptionTest1 {public static void f(){System.out.println("f()");throw new RuntimeException();}public static void main(String[] args) {System.out.println("start main");try{f();}catch(Exception e){e.printStackTrace();//打印异常}System.out.println("end main");}}

执行过程：输出start main 调用f,输出f()，抛出异常，捕获，打印异常堆栈，输出end main

start mainf()java.lang.RuntimeException                                                       //输出异常全路径at exceptiontest.test.ExceptionTest1.f(ExceptionTest1.java:7)            //跟上一个一样at exceptiontest.test.ExceptionTest1.main(ExceptionTest1.java:14)end main

2）打印所有异常的方法

package exceptiontest.test;public class ExceptionTest1 {public static void f(){System.out.println("f()");throw new RuntimeException();}public static void main(String[] args) {System.out.println("start main");try{f();}catch(Exception e){e.printStackTrace();System.out.println(e);System.out.println(e.getMessage());System.out.println(e.getLocalizedMessage());System.out.println(e.getCause());System.out.println(e.getStackTrace());}System.out.println("end main");}}

输出结果：

start mainf()java.lang.RuntimeExceptionat exceptiontest.test.ExceptionTest1.f(ExceptionTest1.java:6)at exceptiontest.test.ExceptionTest1.main(ExceptionTest1.java:12)java.lang.RuntimeException                                                    //异常全路径null                                                                          //e.getMessagenull                                                                          //e.getLocalizedMessagenull                                                                          //e.getCause[Ljava.lang.StackTraceElement;@184ec44                                        //e.getStackTraceend main

3)初始化信息

package exceptiontest.test;public class ExceptionTest1 {public static void f(){System.out.println("f()");throw new RuntimeException("空指针异常",new NullPointerException());}public static void main(String[] args) {System.out.println("start main");try{f();}catch(Exception e){e.printStackTrace();System.out.println(e);System.out.println(e.getMessage());System.out.println(e.getLocalizedMessage());System.out.println(e.getCause());for(StackTraceElement element : e.getStackTrace()){System.out.println(element.getClassName()+","+element.getFileName()+","+element.getLineNumber()+","+element.getMethodName());}}System.out.println("end main");}}

输出结果：

start mainf()java.lang.RuntimeException: 空指针异常                                               e.printStackTrace()打印的堆栈信息：后面多了messageat exceptiontest.test.ExceptionTest1.f(ExceptionTest1.java:6)at exceptiontest.test.ExceptionTest1.main(ExceptionTest1.java:12)Caused by: java.lang.NullPointerException                                            增加caused by 异常链... 2 morejava.lang.RuntimeException: 空指针异常                                               e.toString空指针异常空指针异常java.lang.NullPointerException                                                       e.getCauseexceptiontest.test.ExceptionTest1,ExceptionTest1.java,6,f                            className，fileName,行数，方法   exceptiontest.test.ExceptionTest1,ExceptionTest1.java,12,main                           end main

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