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java - closing inaccesible resources

问题描述

How to manage the right way the state of a resource?

in java, sometimes we have resources that must to be opened and closed like

Scanner sc = new Scanner(File);
sc.close();

in complex scenarios is not that easy.

i'm facing this problem

foo(){
  return new ClosableResourse();
}

bar(ClosableResourse foo){
  return new NotAccesibleFoo(foo);
}

and 2 entities using this NotAccesibleFoo. How i can properly close my ClosableResource class?

bar() function is the only place where i can close that, but is needed in other entities and not accesible from them.

标签： javaoop

解决方案

这里的工作示例

考虑 Java 的try-with-resources特性，以及这个例子：

public class Example {
    public static void main(String[] args) {
        try (Bar b = new Bar()) {
            b.bar();
        }
    }
}

在这里，如果Bar实现AutoCloseable，则close()自动调用。这可能与您的问题代码不完全匹配，但您可以close()像这样链接：

class CloseableResource implements AutoCloseable {
    @Override
    public void close() {
        System.out.println("TRACER CR close");
    }
}

class Foo implements AutoCloseable {
    CloseableResource resource = new CloseableResource();

    @Override
    public void close() {
        System.out.println("TRACER Foo close");
        resource.close();
    }
}

class Bar implements AutoCloseable {
    Foo foo = new Foo();

    void bar() {} 

    @Override
    public void close() {
        System.out.println("TRACER Bar close");
        foo.close();
    }
}

在这种情况下，客户端代码（例如Example.java这里）使用 try-with-resources 模式很重要。

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