在Java中尝试使用资源时,当抛出异常时关闭资源?[副本]

从 docs :

try with resources语句中声明的资源是 Buffered阅读器。声明语句出现在括号内 紧随try关键字之后。Java中的BufferedReader类 SE 7及更高版本实现了java.lang.AutoCloseable接口。 因为BufferedReader实例是在使用资源的try中声明的 语句,无论try语句是否正确,它都将被关闭 正常或突然完成(由于该方法 BufferedReader.readLine抛出IOException)。

基本上,它相当于:

BufferedReader br = new BufferedReader(new FileReader(System.in));
try {
    int i = Integer.parseInt(br.readLine());
    System.out.println(i);
} finally {
    br.close();
}

让我们尝试一下(从这里开始一个工作示例):

//class implementing java.lang.AutoCloseable
public class ClassThatAutoCloses implements java.lang.AutoCloseable {

    
    public ClassThatAutoCloses() {}
    
    public void doSomething() {
        
        System.out.println("Pippo!");
    }
    
    
    @Override
    public void close() throws Exception {
    
        throw new Exception("I wasn't supposed to fail"); 
        
    }

}

//the main class
public class Playground {

    /**
     * @param args
     */
    public static void main(String[] args) {
        
        //this catches exceptions eventually thrown by the close
        try {
            
            try(var v = new ClassThatAutoCloses() ){
                
                v.doSomething();
                
            }
        } catch (Exception e) {
            //if something isn't catched by try()
            //close failed will be printed
            System.err.println("close failed");
            e.printStackTrace();
        }
    }

}

//the output
Pippo!
close failed
java.lang.Exception: I wasn't supposed to fail
    at ClassThatAutoCloses.close(ClassThatAutoCloses.java:26)
    at Playground.main(Playground.java:24)

try with resources语句中抛出的异常被抑制。try块内抛出的异常会被传播。因此,在您的情况下,catch块将捕获解析异常(如果有的话)。

有关更多详细信息,请参阅 docs .