详略。。。设计模式4——装饰模式。。。studying

设计模式4——装饰模式

★ 场景和问题

在不对原有对象类进行修改的基础上，如何给一个或多个已有的类对象提供增强额外的功能？

★ 引例

写一个MyBufferedReader类，使它能够对字符流(如FileReader、InputStreamReader和PipedReader等)进行功能增强：
(1) 提供带缓冲的myRead()方法，对原有的read()方法进行增速；
(2)提供一个能够每次读取一行字符的myReadLine()方法。

图片解释：

Java代码实现思想：

简易版：

package cn.hncu.patterns.exercise.decorator;import java.io.BufferedReader;import java.io.FileReader;import java.io.IOException;public class Test {static String dir = "a.txt";// 相对路径/* * 这里只是为了演示， * 没有关流 */public static void main(String[] args) {try {// read();// myRead();// readLine();myReadLine();} catch (IOException e) {e.printStackTrace();}}private static void myReadLine() throws IOException {MyBufferedReader br = new MyBufferedReader(new FileReader(dir));String aline = "";while ((aline = br.myReadLine()) != null) {System.out.println(aline);}}private static void readLine() throws IOException {BufferedReader br = new BufferedReader(new FileReader(dir));String aline = "";while ((aline = br.readLine()) != null) {System.out.println(aline);}}private static void myRead() throws IOException {MyBufferedReader br = new MyBufferedReader(new FileReader(dir));int ch = 0;while ((ch = br.myRead()) != -1) {System.out.print((char) ch);}System.out.println();}private static void read() throws IOException {BufferedReader br = new BufferedReader(new FileReader(dir));int ch = 0;while ((ch = br.read()) != -1) {System.out.print((char) ch);}System.out.println();}}

package cn.hncu.patterns.exercise.decorator;import java.io.Closeable;import java.io.FileReader;import java.io.IOException;/* * 装潢模式本质： * 对某个类功能的加强。 */public class MyBufferedReader implements Closeable {/* * buf-缓存，用来提速 * fr-目标类 * count-记录缓存中数据的个数 * position-记录缓存中数据的位置 */private char[] buf = new char[1024];private FileReader fr = null;private int count = 0;private int position = 0;/* * 模仿API中的BufferedReader类的构造函数 */public MyBufferedReader(FileReader fr) {this.fr = fr;}/* * 模仿API中的BufferedReader类中的函数, */public int myRead() throws IOException {if (count == 0) {count = fr.read(buf);position = 0;}if (count < 0) {return -1;}char ch = buf[position];position++;count--;return (int) ch;}public String myReadLine() throws IOException {StringBuffer sb = new StringBuffer();int ch = 0;while ((ch = myRead()) != -1) {/* * 回车换行符不要 */if (ch == '\r') {continue;}if (ch == '\n') {return sb.toString();}sb.append((char) ch);}if (sb.length() != 0) {return sb.toString();}return null;}@Overridepublic void close() throws IOException {fr.close();}}

演示图片：

测试文件：

BufferedReader---read()

BufferedReader---readLine()

MyBufferedReader---myRead()

MyBufferedReader---myReadLine()

实现版：

package cn.hncu.patterns.exercise.decorator;import java.io.Closeable;import java.io.IOException;import java.io.Reader;/* * 装潢模式本质： * 对某个类功能的加强。 */public class MyBufferedReader extends Reader implements Closeable {/* * buf-缓存，用来提速 * fr-目标类 * count-记录缓存中数据的个数 * position-记录缓存中数据的位置 */private char[] buf = new char[1024];private Reader fr = null;private int count = 0;private int position = 0;/* * 模仿API中的BufferedReader类的构造函数 */public MyBufferedReader(Reader fr) {this.fr = fr;}/* * 模仿API中的BufferedReader类中的函数, */public int myRead() throws IOException {if (count == 0) {count = fr.read(buf);position = 0;}if (count < 0) {return -1;}char ch = buf[position];position++;count--;return (int) ch;}public String myReadLine() throws IOException {StringBuffer sb = new StringBuffer();int ch = 0;while ((ch = myRead()) != -1) {/* * 回车换行符不要 */if (ch == '\r') {continue;}if (ch == '\n') {return sb.toString();}sb.append((char) ch);}if (sb.length() != 0) {return sb.toString();}return null;}@Overridepublic void close() throws IOException {fr.close();}@Overridepublic int read(char[] cbuf, int off, int len) throws IOException {return 0;}}