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;
	}

	@Override
	public 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;
	}

	@Override
	public void close() throws IOException {
		fr.close();
	}

	@Override
	public int read(char[] cbuf, int off, int len) throws IOException {
		return 0;
	}

}