java 中的各种奇怪的执行顺序之异常篇

太过爱你忘了你带给我的痛 2022-03-22 04:40 138阅读 0赞

try{ 
    statement1;
    } 
    catch(ExceptionType1 e1){ 
      statement2;
    } catch(ExceptionType2 e2){ 
    
    statement3;
    
    }finally{ 
    statement4;
    }

## 情况讨论: ##

*  1,statement1 抛出异常e,如果e是e1类型或子类型,那么就会进入 statement2,不会进入 statement3,如果 statement2 含return,那么会先进入finally,再执行return(如果statement4中含return,那么只会执行这个return);

测试代码:

public static String test001(int a) { 
            try { 
              if(a==1){ 
                  throw new Exception();
              }
                return "try block";
    
            } catch (Exception e) { 
    
                System.out.println(" catch block");
                return "catch return";
            } finally { 
                System.out.println(" finally block");
                return " finally return";
            }
        }
     public static void main(String[] args) { 
            System.out.println("main:"+test001(1));
            }

输出:  
![在这里插入图片描述][20190125222856757.png]

1.  未抛出异常,如果statement1 有return,那么先进入finally再进入statement1的return (如果finally 有return 那么只能进入finally的return)  
    测试代码:

public class TryCatch { 
        public static void main(String[] args) { 
            System.out.println("main:" + test002());
        }
    
        public static String test002() { 
            try { 
    
                return "try block";
    
            } catch (Exception e) { 
    
                System.out.println(" catch block");
            } finally { 
                System.out.println(" finally block");
    // return " finally return";
            }
    
            return "result";
        }
    }

效果:finally不含return  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM2OTIyOTI3_size_16_color_FFFFFF_t_70]finally 含return:

![在这里插入图片描述][20190125223202826.png]

## 总结 ##

*  try 通常与catch连用,但是并不一定需要与catch连用  
    可以是try\{\}finally\{\}
 *  try \{\}catch()\{ExceptionType1 e1\}catch(ExceptionType e2)\{\},如果抛出的异常不是ExceptionType1类型或者其子类型,那么就交给下一个catch处理(继续判断类型)
 *  return 只会执行一次.如果finally有return,那么只会执行这个return
 *  finally 中没有return,try 或者catch有return,那么需要先执行try,catch,然后finally,最后执行对应的return

[20190125222856757.png]: /images/20220322/f74eb752375f42f4bb525491f95aa274.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM2OTIyOTI3_size_16_color_FFFFFF_t_70]: /images/20220322/646b82f6e33f465ca1a4f810920eac1d.png
[20190125223202826.png]: /images/20220322/0fc27c448eed4abdad5ba98860452efc.png