Decorative design mode

Decorative design pattern

1. Decorative design mode:

• When you want to enhance the functionality of an existing object, you can define a class, pass in an existing object, and, based on the functionality of an existing object, and provide enhancements, the defined class is called an ornament class;
• The adornment class usually receives the decorated object through the constructor function, and provides the stronger function based on the function of the decorated object;

such as: BufferedStream (InputStream in);

BufferedStream is a decorative class based on InputStream.

2. The difference between decoration and inheritance:

• decoration class because of the enhancement of existing objects, has the same function and has the same, but provides more powerful function; Decorative and decorated classes usually belong to the same system;

/* * Customize a decorated class with line number Mylinenumberreader */package unit15;import java.io.*;class Mylinenumberreader extends mybufferedreader{//Decoration class private Reader r;private int linenumber; Mylinenumberreader (reader R) {///Based on polymorphic thought, use Reader as the Parameter object class super (r);} Public String Mylinenumberreaderline () throws ioexception{     linenumber++;     Return super. Myreadline ();} public void Setlinenumber (int linenumber) {this.linenumber = linenumber;} public int Getlinenumber () {return linenumber;} public void Myclose () throws Ioexception{r.close ();}} public class Mylinenumbertest {public static void main (String args[]) {try {FileReader fr = new FileReader ("Src/unit15/file Writertest.java "); Mylinenumberreader MLR = new Mylinenumberreader (FR); String str = null;while ((STR=MLR). Mylinenumberreaderline ())!=null) {System.out.println (str);} Mlr. Myclose ();} catch (IOException e) {//TODO auto-generated catch Blocke.printstacktrace ();}}}

　　

3. The application of decoration design pattern is most common in IO input/output, and two of them are more important:

• InputStreamReader (InputStream in);
• Outputsteamwriter (OutputStream out); Convert Stream

This method is very useful in keyboard input and output:

Example:

1  Packageunit15;2 3 ImportJava.io.*;4 5  Public classTransfreamtest {6      Public Static voidMain (String args[]) {7InputStream in =system.in;8InputStreamReader ISR =NewInputStreamReader (in);9BufferedReader BFR =NewBufferedReader (ISR);TenBufferedreadser buf = new BufferedReader (new Inputsream (system.in));//keyboard Input combination format OneOutputStream out =System.out; AOutputStreamWriter OSW =NewOutputStreamWriter (out); -BufferedWriter BRW =NewBufferedWriter (OSW); -BufferedWriter BFW = new BufferedWriter (new Outputsteam (System.out));//Output to console the          -String str =NULL; -         Try { -              while((Str=bfr.readline ())! =NULL){ +                 if("Over". Equals (str)) -                      Break; +                 //System.out.println (str); A brw.write (str); at brw.newline (); - Brw.flush (); -                  -             } - bfr.close (); - brw.close (); in}Catch(IOException e) { -             //TODO auto-generated Catch block to e.printstacktrace (); +         } -              the     } *  $}

Decorative design mode