Exception

异常捕获

• 将代码块选中->ctrl+alt+t->选中try-catch

01:

public class Exception01 {public static void main(String[] args) {int n1 = 10;int n2 = 0;try {int res = n1/n2;} catch (Exception e) {
//            e.printStackTrace();System.out.println(e.getMessage());}System.out.println("continue");}
}

异常介绍

基本概念

异常体系图和小结

常见的运行时异常

01：

public class ExceptionDemo {public static void main(String[] args) {String name = null;System.out.println(name.length());}//    Exception in thread "main" java.lang.NullPointerException: Cannot invoke "String.length()" because "name" is null
//    at WeekDemo02.ExceptionDemo.main(ExceptionDemo.java:6)}

编译异常

小练习

异常处理

try-catch异常处理

try-catch方法处理异常-注意事项

01:

package TryDemo;public class TryCatchDetail {public static void main(String[] args) {try {String str = "123";int a = Integer.parseInt(str);System.out.println("a");} catch (NumberFormatException e) {System.out.println(e.getMessage());}System.out.println("continue");//        a
//        continue}
}//================================================================================package TryDemo;public class TryCatchDetail {public static void main(String[] args) {try {String str = "HSPEDU";int a = Integer.parseInt(str);System.out.println("a");//这条代码运行不到} catch (NumberFormatException e) {System.out.println(e.getMessage());}System.out.println("continue");//        For input string: "HSPEDU"
//        continue}
}//============================================================================package TryDemo;public class TryCatchDetail {public static void main(String[] args) {try {String str = "123";int a = Integer.parseInt(str);System.out.println("a");} catch (NumberFormatException e) {System.out.println(e.getMessage());}finally {System.out.println("123");}System.out.println("continue");//        a
//        123
//        continue}
}//====================================================================================package TryDemo;public class TryCatchDetail {public static void main(String[] args) {try {String str = "HSP";int a = Integer.parseInt(str);System.out.println("a");} catch (NumberFormatException e) {System.out.println(e.getMessage());}finally {System.out.println("123");}System.out.println("continue");//        For input string: "HSP"
//        123
//        continue}
}

小练习

try-catch-finally执行顺序小结

小练习

throws异常处理

注意事项和使用细节

自定义异常

01:

package TryCatchExercise;import SuperWorkDemo.A;public class CustomException {public static void main(String[] args) {int age = 10000;if (!(age >= 18 && age <= 120)){throw new AgeException("age need a range of 18——120");}System.out.println("ok");//Exception in thread "main" TryCatchExercise.AgeException: age need a range of 18——120//	at TryCatchExercise.CustomException.main(CustomException.java:12)}
}//自定义异常
class AgeException extends RuntimeException
{//构造器public AgeException(String message) {super(message);}
}

throw和throws的区别

小练习

大练习

01:

package TryCatchExercise;public class homeWork {public static void main(String[] args) {try {if (args.length!=2){throw new ArrayIndexOutOfBoundsException("参数个数不对");}int n1 = Integer.parseInt(args[0]);int n2 = Integer.parseInt(args[1]);double res = cal(n1,n2);System.out.println(res);} catch (ArrayIndexOutOfBoundsException e) {System.out.println(e.getMessage());}catch(NumberFormatException e){System.out.println("参数格式不正确，需要输入整数");}catch(ArithmeticException e){System.out.println("出现了除0的异常");}}public static double cal(int n1,int n2){return n1/n2;}
}

02:

03：

04：