Try with resource close resource flow

•  JDK7 Close stream resource before

    public void oldCopyFile(String orignalUrl,String targetUrl){
        InputStreamReader is = null;
        OutputStreamWriter os = null;

        try {
            is = new InputStreamReader(new FileInputStream(orignalUrl));
            os = new OutputStreamWriter(new FileOutputStream(targetUrl));
            char[] arr = new char[2048];
            while (is.read(arr) != -1){
                os.write(arr);
            }
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        // Need to be in final In it, various flows are closed manually , It's very cumbersome 
        }finally {
            if (os != null){
                try {
                    os.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (is != null){
                try {
                    is.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }

• JDK7 Close stream resource :try-with-resource: It is not necessary to manually close the flow

   /** 
     * try(
     *    It is declared in parentheses 
     * ){
     *    Resources are used in the execution body 
     * }
     */

    public void NewCopyFile(String orignalUrl,String targetUrl){

        try (
                InputStreamReader is = new InputStreamReader(new FileInputStream(orignalUrl));
                OutputStreamWriter os = new OutputStreamWriter(new FileOutputStream(targetUrl));
        ){
            char[] arr = new char[2048];
            while (is.read(arr) != -1){
                os.write(arr);
            }
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

• try-with-resource brief introduction

  • Java7 Introducing new features

  • Closing resources gracefully

  • A kind of Java Grammatical sugar : After decompilation, it still adopts jdk7 Close the flow as before

• try-with-resource Use

  • Automatic shutdown of multiple resources

  • Resources that need to be automatically closed need to be implemented AutoCloseable Interface

  • Avoid abnormal shielding ( Will throw out exceptions layer by layer )

• Special case of resource shutdown

  • Resource object is return Under the circumstances , Closed by caller

    • At this point, the resource is closed inside the method , The resources obtained by the caller are not available

  • ByteArrayInputStream No need to close

  • Use Socket Acquired InputStream and OutputStream Object does not need to be closed

    • InputStream and OutputStream Closing an object will result in Socket close

    • call Socket Of shutdowmInput and shutdownOutput: Will only turn off based on Socket Input and output streams without closing the entire Socket Connect