try(){}的简单理解

柔光的暖阳◎ 2023-02-22 12:22 32阅读 0赞

以前使用try catch-finally都是捕获异常,然后流关闭等等,代码总是这样的:好比往FileOutputStream写东西:

@Test
      public void test2() throws IOException { 
        File file = new File("E://test");
        if (!file.exists()) { 
          file.createNewFile();
        }
        FileOutputStream fileOutputStream = new FileOutputStream(file);
        try { 
          System.out.println("do something...");
          fileOutputStream.write("aaa".getBytes());
          fileOutputStream.flush();
        } catch (Exception e) { 
          System.out.println("do ...");
        } finally { 
          fileOutputStream.close();
        }
      }

这样写很难受,可以进行优化,将FileOutputStream fileOutputStream = new FileOutputStream(file)放到try()里面,也可以放多个,

@Test
      public void test2() throws IOException { 
        File file = new File("E://test");
        if (!file.exists()) { 
          file.createNewFile();
        }
       
        try( FileOutputStream fileOutputStream = new FileOutputStream(file);) { 
          System.out.println("do something...");
          fileOutputStream.write("aaa".getBytes());
          fileOutputStream.flush();
        } catch (Exception e) { 
          System.out.println("do ...");
        } 
      }

try()里每个声明的变量类型都必须是Closeable的子类,就一个close方法;相当于系统自动将关闭操作放到了finally里面而不需要我们自己写了,很nice;  
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