Day08__异常

异常

Error和Exception

捕获和抛出异常

package exception;

public class Demo01 {
    public static void main(String[] args) {
        int a=1;
        int b=0;

        //Ctrl+Alt+t
        try {//try监控区域
            System.out.println(a/b);
        }catch (ArithmeticException e){//捕获异常
            System.out.println("除数不能为0");
        }finally {//处理善后工作
            System.out.println("finally");
        }

        //finally 可以不要finally  ，eg：IO资源关闭

        System.out.println("====================");

        //多捕获要从小到大
        try {//try监控区域
            System.out.println(a/b);
        }catch (Error e){//捕获异常
            System.out.println("Error");
        }catch (Exception e){
            System.out.println("Exception");
        }catch (Throwable e){
            System.out.println("Throwable");
        }

        System.out.println("====================");

        //多捕获要从小到大
        try {//try监控区域
            new Demo01().test(1,0);
        } catch (ArithmeticException e){
            e.printStackTrace();
        }

        System.out.println("====================");
    }


    //假设这个方法中处理不了这个异常，方法上抛出异常
    public void test(int a,int b) throws ArithmeticException{
        if(b==0){
            throw new ArithmeticException();//主动抛出异常,一般在方法中使用
        }
    }

}

自定义异常及经验小结

package exception;

public class MyException extends Exception{

    //传递数字>10；
    private int detail;
    public MyException(int a){
        this.detail = a;
    }

    //toString:异常的打印信息
    @Override
    public String toString() {
        return "MyException{" +
                "detail=" + detail +
                '}';
    }
}

package exception;

public class Test {
    //可能存在异常的方法
    static void test(int a) throws MyException {

        System.out.println("传递的参数为"+a);

        if(a>10){
            throw new MyException(a);
        }

        System.out.println("OK");
    }

    public static void main(String[] args) {
        try{
            test(1);
        }catch (MyException e){
            System.out.println("MyException=>"+e);
        }

        try{
            test(11);
        }catch (MyException e){
            System.out.println("MyException->"+e);
        }
    }
}