Java 7 新的 try-with-resources 語法(Auto Source release )

出處: OSChina : https://www.oschina.net/question/12_10706
作者：@红薯

從 Java 7 build 105 版本開始，Java 7 的編譯器和運行環境已支援新的 try-with-resources 語法，稱為 ARM (Automatic Resource Management) ，自動資源管理。
新的語句支援包括流以及任何可關閉的資源，例如，一般我們會編寫如下代碼來釋放資源：

private static void customBufferStreamCopy(File source, File target) {
    InputStream fis = null;
    OutputStream fos = null;
    try {
        fis = new FileInputStream(source);
        fos = new FileOutputStream(target);
 
        byte[] buf = new byte[8192];
 
        int i;
        while ((i = fis.read(buf)) != -1) {
            fos.write(buf, 0, i);
        }
    }
    catch (Exception e) {
        e.printStackTrace();
    } finally {
        close(fis);
        close(fos);
    }
}
 
private static void close(Closeable closable) {
    if (closable != null) {
        try {
            closable.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

而使用 try-with-resources 語法來簡化如下：
private static void customBufferStreamCopy(File source, File target) {
    try (InputStream fis = new FileInputStream(source);
        OutputStream fos = new FileOutputStream(target)){
 
        byte[] buf = new byte[8192];
 
        int i;
        while ((i = fis.read(buf)) != -1) {
            fos.write(buf, 0, i);
        }
    }
    catch (Exception e) {
        e.printStackTrace();
    }
}


or

public static void customBufferStreamCopy(String[] args) throws Exception{
 @Cleanup InputStream in = new FileInputStream(args[0]);
 @Cleanup OutputStream out = new FileOutputStream(args[1]);
 byte[] buf = new byte[8192];       
        int i;  
        while ((i = in.read(buf)) != -1) {  
            out.write(buf, 0, i);  
        }  
}