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在我们使用资源时，一般资源使用完毕，都需要把资源关闭掉，在JDK7之前，我们一般都是使用try-catch-finally在finally中进行资源的关闭。

示例如下：

public static void test1(){        FileInputStream ins = null;        FileOutputStream out = null;        try {            ins = new FileInputStream(new File("G://aa.text"));            out = new FileOutputStream(new File("G://bb.text"));            //业务逻辑        }catch (FileNotFoundException ex){            ex.printStackTrace();        }finally {            //关闭资源            if(ins != null){                try {                    ins.close();                }catch (Exception insex){                    insex.printStackTrace();                }            }            if(out != null){                try {                    out.close();                }catch (Exception outex){                    outex.printStackTrace();                }            }        }    }

我们使用了输入流和输出流，在使用完后，需要手动去关闭。

在jdk7后，提供了一种新的方式：try-with-resources 方式来管理资源，在try中声明资源，当程序执行完后，会自动将声明的资源关闭掉，方式如下：

public static void test2(){        try(FileInputStream ins = new FileInputStream(new File("G:/aa.text"));            FileOutputStream out = new FileOutputStream(new File("G://bb.text"))){            //业务逻辑        }catch (FileNotFoundException fnex){            fnex.printStackTrace();        }catch (IOException ioex){            ioex.printStackTrace();        }    }

附：

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.     *     * 
 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     * mark the {@code Closeable} as closed, prior to throwing     * the {@code IOException}.     *     * @throws IOException if an I/O error occurs     */    public void close() throws IOException;}

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