Closeable接口

Closeable接口继承于AutoCloseable，主要的作用就是自动的关闭资源，其中close()方法是关闭流并且释放与其相关的任何方法，如果流已被关闭，那么调用此方法没有效果，像InputStream和OutputStream类都实现了该接口，源码如下

/*
 * Copyright (c) 2003, 2013, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */
 
package java.io;
 
import java.io.IOException;
 
/**
 * A {@code Closeable} is a source or destination of data that can be closed.
 * The close method is invoked to release resources that the object is
 * holding (such as open files).
 *
 * @since 1.5
 */
public interface Closeable extends AutoCloseable {
 
    /**
     * Closes this stream and releases any system resources associated
     * with it. If the stream is already closed then invoking this
     * method has no effect.
     *
     * <p> As noted in {@link AutoCloseable#close()}, cases where the
     * close may fail require careful attention. It is strongly advised
     * to relinquish the underlying resources and to internally
     * <em>mark</em> the {@code Closeable} as closed, prior to throwing
     * the {@code IOException}.
     *
     * @throws IOException if an I/O error occurs
     */
    public void close() throws IOException;
}

Closeable用法
1.在1.7之前，我们通过try{} finally{} 在finally中释放资源。

2.对于实现AutoCloseable接口的类的实例，将其放到try后面（我们称之为：带资源的try语句），在try结束的时候，会自动将这些资源关闭（调用close方法）。

package com.canal.demo;

import java.io.Closeable;
import java.io.IOException;

public class CloseableTest implements Closeable {
    public static void test1() {
        try {
            System.out.println("test1方法 处理逻辑");
        } catch (Exception e) {
            System.out.println("test1方法 异常处理");
        } finally {
            System.out.println("test1方法 释放资源");
        }
    }
    public static void test2() {
        try (CloseableTest c = new CloseableTest()) {
            System.out.println("test2方法 处理逻辑");
        } catch (Exception e) {
            System.out.println("test2方法 处理异常");
        }
    }
    @Override
    public void close() throws IOException {
        System.out.println("test2方法这里自动释放资源");
    }

    public static void main(String[] args) {
        test1();
        test2();
    }
}

解释：
因为test2中将该类创建对象的过程放置在了try语句中，所以test2会进行自动的资源释放

运行结果：
test1方法 处理逻辑
test1方法 释放资源
test2方法 处理逻辑
test2方法这里自动释放资源