异常02：捕获和抛出异常

异常处理机制

• 抛出异常

• 捕获异常

• 异常处理五个关键字

  • try、catch、finally、throw、throws

package com.exception;

public class Demo01 {
    public static void main(String[] args) {
        new Demo01().a();
    }
    public void a(){
        b();
    }

    public void b(){
        a();
    }
}

package com.exception;

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

        try {  //try监控区域    Ctrl+Alt+T
            System.out.println(a/b);

        } catch (ArithmeticException e) {   //catch 捕获异常
            System.out.println("除数不能为零");
        } finally {  //处理善后工作   finally可以不要，一般用于IO、资源等关闭
            System.out.println("finally");
        }
        System.out.println("123");  //处理完异常之后123正常打印，否则程序就终止了
    }
}

package com.exception;

public class Test02 {
    public static void main(String[] args) {
        try {
            new Test02().b();
        } catch (Error e) {
            System.out.println("Error");
        }catch(Exception e){
            System.out.println("Exception");
        }catch(Throwable e){
            System.out.println("Throwable");
        }
        finally {
            System.out.println("finally");
        }

    }
    public void a(){b();}
    public void b(){a();}

}

package com.exception;

public class Test03 {
    public static void main(String[] args) {
        int a = 1;
        int b = 0;

        if (b == 0) { // 主动抛出异常throw throws  一般放在方法中参见Test04
            throw new ArithmeticException();
        }
    }
}

package com.exception;

public class Test04 {
    public static void main(String[] args) {
        new Test04().test(1,0);
    }

    public void test(int a,int b){
        if(b==0){
            throw new ArithmeticException(); //主动抛出异常
        }
    }
}

package com.exception;

public class Test05 {
    public static void main(String[] args) {
        try {
            new Test04().test(1,0);
        } catch (ArithmeticException e) {
            e.printStackTrace();
            System.out.println("b不能为0");
        }
        System.out.println("123");
    }

    //如果这个方法无法处理这个异常，那么就将异常抛出，然后再用try..catch去捕获
    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
        }
    }
}