import javax.swing.*; class AboutException { public static void main(String[] a) { int i=1, j=0, k; // k=i/j; try { k = i/j; //Causes division-by-zero exception throw new Exception("Hello.Exception!"); } catch ( ArithmeticException e) { System.out.println("被0除. "+ e.getMessage()); } catch (Exception e) { if (e instanceof ArithmeticException) System.out.println("被0除"); else { System.out.println(e.getMessage()); } } finally { JOptionPane.showConfirmDialog(null,"OK"); } } }
try catch finally捕捉错误可以让我们快速的找到我们错误的原因
try来捕捉错误通过catch中的e参数来报出错误的原因可以在finally预先设置好出错之后也会输出的句式。
public class CatchWho { public static void main(String[] args) { try { try { throw new ArrayIndexOutOfBoundsException(); } catch(ArrayIndexOutOfBoundsException e) { System.out.println( "ArrayIndexOutOfBoundsException" + "/内层try-catch"); } throw new ArithmeticException(); } catch(ArithmeticException e) { System.out.println("发生ArithmeticException"); } catch(ArrayIndexOutOfBoundsException e) { System.out.println( "ArrayIndexOutOfBoundsException" + "/外层try-catch"); } } }
这个代码是try捕捉到抛出的那个异常，然后匹配到的异常处理，然后又抛出了一个异常，这个异常匹配到了异常处理，所以最下面的那个没有被执行。
输出结果是
ArrayIndexOutOfBoundsException/内层try-catch
发生ArithmeticException
public class CatchWho2 { public static void main(String[] args) { try { try { throw new ArrayIndexOutOfBoundsException(); } catch(ArithmeticException e) { System.out.println( "ArrayIndexOutOfBoundsException" + "/内层try-catch"); } throw new ArithmeticException(); } catch(ArithmeticException e) { System.out.println("发生ArithmeticException"); } catch(ArrayIndexOutOfBoundsException e) { System.out.println( "ArrayIndexOutOfBoundsException" + "/外层try-catch"); } } }
这个异常捕捉是：先抛出异常然后异常不匹配，下面又有一个异常想抛出，但是这个异常还没有被处理所以这个新的异常不会被抛出，第一个异常与下啊一个也不匹配，直到最后那个可以与它匹配的异常处理才结束了第一个抛出的异常
所以输出结果是：
ArrayIndexOutOfBoundsException/外层try-catch
public class EmbededFinally { public static void main(String args[]) { int result; try { System.out.println("in Level 1"); try { System.out.println("in Level 2"); // result=100/0; //Level 2 try { System.out.println("in Level 3"); result=100/0; //Level 3 } catch (Exception e) { System.out.println("Level 3:" + e.getClass().toString()); } finally { System.out.println("In Level 3 finally"); } //result=100/0; //Level 2 } catch (Exception e) { System.out.println("Level 2:" + e.getClass().toString()); } finally { System.out.println("In Level 2 finally"); } // result = 100 / 0; //level 1 } catch (Exception e) { System.out.println("Level 1:" + e.getClass().toString()); } finally { System.out.println("In Level 1 finally"); } } }
通过修改result=100/0的位置来测试，我们可以看到他的异常处理是根据他所在的“层”来优先进行匹配
public class SystemExitAndFinally { public static void main(String[] args) { try{ System.out.println("in main"); throw new Exception("Exception is thrown in main"); //System.exit(0); } catch(Exception e) { System.out.println(e.getMessage()); System.exit(0); } finally { System.out.println("in finally"); } } }
这个代码的结果我们可以看出System.exit(0)可以结束进程不运行finally的内容
// UsingExceptions.java // Demonstrating the getMessage and printStackTrace // methods inherited into all exception classes. public class PrintExceptionStack { public static void main( String args[] ) { try { method1(); } catch ( Exception e ) { System.err.println( e.getMessage() + "\n" ); e.printStackTrace(); } } public static void method1() throws Exception { method2(); } public static void method2() throws Exception { method3(); } public static void method3() throws Exception { throw new Exception( "Exception thrown in method3" ); } }
控制台输出：
import java.util.Scanner; class MyException extends Exception { public MyException(String Message) { super(Message); } public MyException(String message, Throwable cause) { super(message, cause); } public MyException( Throwable cause) { super(cause); } } public class text { public static void throwExceptionMethod() throws MyException { try { //System.out.println( "Method throwException" ); throw new Exception("输入错误"); } catch( Exception e ) { //System.err.println( // "Exception handled in method throwException" ); //转换为一个自定义异常，再抛出 throw new MyException("输入错误"); } finally { } // any code here would not be reached } public static void main(String[] args) { Scanner shuru=new Scanner(System.in); int a; System.out.println("请输入"); try { a=shuru.nextInt(); } catch(Exception e) { try { throwExceptionMethod(); } catch(MyException e1) { System.err.println(e1.getMessage()); } } } }
这个是自己定义的一个关于输入异常的捕捉，如果输入的不是int类型他就会报错
原文：https://www.cnblogs.com/yizhixiaozhu/p/11782221.html