048 异常

什么是异常

异常体系结构

异常的继承关系

Error

Exception

异常处理机制

try：用{}将可能产生异常的代码包裹
catch：与try搭配使用，捕获try包裹代码中抛出的异常并进行后续动作
finally：跟在try后，在try和catch之后执行，可用于关闭资源或后续处理
throw：手动抛出一个异常
throws：

处理异常

public class ErrorTest {public static int division(int a, int b) throws Exception {if(a % b != 0){throw new Exception("不好意思除不开");}return a / b;}
}class TestClass {public static void main(String[] args) {int num1 = 4;int num2 = 3;int division= 0;try {division = ErrorTest.division(num1, num2);} catch (ArithmeticException e) {System.out.println("算数异常");} catch (Exception e) {System.out.println("产生了异常，关键信息如下：");e.printStackTrace();} finally {System.out.println("进行一些善后工作");}System.out.println(division);}
}

自定义异常

public class ErrorTest {public static int division(int a, int b) throws Exception {if(a <= 0){throw new MyException(a);}return a / b;}
}class MyException extends Exception{private int num;public MyException(int num) {this.num = num;}@Overridepublic String toString() {return "MyException{" +"num=" + num +'}';}
}class TestClass {public static void main(String[] args) {int num1 = -4;int num2 = 2;try {ErrorTest.division(num1, num2);} catch (MyException e) {System.out.println("产生了异常，关键信息如下：");e.printStackTrace();} catch (Exception e) {System.out.println("产生了异常，关键信息如下：");e.printStackTrace();}}
}