java7 [try-with-resources]

た入场券 2024-02-18 00:14 7阅读 0赞

## try-with-resources ##

JDK7开始，支持[try-with-resources][].

public class Savevarargs {
        
    
            public static void main(String[] args) throws Exception {
    
                try (OneCloseable one = new OneCloseable();
                     TwoCloseable two = new TwoCloseable()) {
                    one.foo();
                    two.foo();
                } catch (Exception e) {
                    System.out.println("bom: " + e.getMessage());
                    Arrays.stream(e.getSuppressed()).forEach(System.out::println);
                }
            }
        }
    
        class OneCloseable implements AutoCloseable {
    
            public OneCloseable() throws Exception {
                // throw new Exception("constructor exception....");
            }
    
            public void foo() throws Exception {
                throw new Exception("one method exception....");
            }
    
            @Override
            public void close() throws Exception {
                System.out.println("one closing.....");
                throw new Exception("one close excep...");
            }
        }
    
        class TwoCloseable implements AutoCloseable {
    
            public TwoCloseable() throws Exception {
                // throw new Exception("constructor exception....");
            }
    
            public void foo() throws Exception {
                throw new Exception("two method exception....");
            }
    
            @Override
            public void close() throws Exception {
                System.out.println("two closing.....");
                throw new Exception("two close excep...");
            }
        }

1.  try模块参数是resources，为`final`类型，不能在try-with-resources模块中再进行赋值
2.  try模块和try-with-resources模块执行如遇异常，将抛出，被catch或者向上抛出。这点和jdk7之前相同
3.  resource定义：实现了`Closable`或者`Autoacloseable`的对象
4.  try或者try-with-resources执行不管是否遇到异常，将调用`resource.close()`
5.  多个resources用分号分隔，`close()`调用顺序与创建顺序相反
6.  如果在当前`resource.close()`中遇到异常，并且此异常不是第一个，当前异常被抑制`e.getSuppressed()`获取被抑制的异常

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[try-with-resources]: https://docs.oracle.com/javase/tutorial/essential/exceptions/tryResourceClose.html