装饰者设计模式

/*装饰设计模式：当想要对已有的对象进行功能增强时，可以定义类，将已有对象传入，基于已有的功能，并提供加强功能。那么自定义的该类成为装饰类。装饰类通常会通过构造方法接收被装饰的对象，并基于被装饰的对象提供更强的功能。装饰类和继承的区别：MyReader //专门用于读取数据的类。继承体系：|--MyTextReader|--MyBufferTextReader|--MyMediaReader|--MyBufferMediaReader|--MyDataReader|--MyBufferDataReaderclass MyBufferReader{private MyBufferTextReader text;private MyBufferMediaReader media;private MyBufferDataReader data;MyBufferReader(MyBufferTextReader text){this.text = text;}MyBufferReader(MyBufferMediaReader media){this.media = media;}MyBufferReader(MyBufferDataReader data){this.data = data;}}上面这个类扩展性很差。找到其参数的共同类型，通过多态的形式，可以提高扩展性。eg：class MyBufferReader extends MyReader{private MyReader r;MyBufferReader(MyReader r){this.r = r;}}通过装饰类优化后：    |--MyTextReader|--MyMediaReader|--MyDataReader|--MyBufferReader装饰模式比继承要灵活，避免了继承体系的臃肿，而且降低了类与类之间的关系。装饰类因为增强已有对象，具备的功能和已有的是相同的，只不过提供了更强的功能。所以装饰类和被装饰类通常都是属于一个体系中的。*/class Person{public void eat(){System.out.println("吃饭");}}/*对Person进行增强*/class SuperPerson{private Person p;SuperPerson(Person p){this.p = p;}public void superEat(){System.out.println("开胃菜");p.eat();System.out.println("甜点");}}class PersonDemo{public static void main(String[] args) {Person p = new Person();//p.eat();SuperPerson sp = new SuperPerson(p);sp.eat();}}/*-----------------------------------------------------------------*//*eg:自定义字符流缓冲区包装类。*/import java.io.*;class MyBufferedReader extends Reader{private Reader r;MyBufferedReader(Reader r){this.r = r;}//可以一次读一行数据的方法public String MyReaderLine()throws IOException{/*定义一个临时容器。原BufferedReader封装的是字符数组。为了演示方便，定义一个StringBuilder容器。因为最终还是要变成字符串。*/StringBuilder sb = new StringBuilder();while((int ch = r.read()) != -1){if(ch == '\r')continue;if(ch == '\n')return sb.toString();elsesb.append((char)ch);}if(sb.length() != 0)return sb.toString();return null;}public void MyClose()throws IOException{r.close();}/*覆盖Reader类中的抽象方法。*/public void close()throws IOException{r.close();}public int read(char[] cbuf,int off,int len)throws IOException{return r.read(cbuf,off,len);}}class MyBufferedReaderDemo{public static void main(String[] args){FileReader fr = null;MyBufferedReader mybr = null;try{fr = new FileReader("copyText.java");mybr = new MyBufferedReader(fr);while((String line = mybr.myReadLine()) != null){System.out.println(mybr.MyReaderLine()+":"+line);}}catch (IOException e){throw new IOException("读写失败！");}finally{try{if(mybr != null)mybr.myClose();}catch (IOException e){throw new IOException("读写失败！");}}}}/*eg:自定义带行号的字符流包装类。*/import java.io.*;class MyLineNumberReader extends MyBufferedReader{//private Reader r;private int lineNumber;MyLineNumberReader(Reader r){//this.r = r;super(r);}/*public String myReadLine(){lineNumber ++;StringBuilder sb = new StringBuilder();while((int ch == r.read) != -1){if(ch == '\r')continue;if(ch == '\n')return sb.toString();elsesb.append((char)ch);}if(sb.length() != 0)return sb.toString();return null;}*/public void setLineNumber(int lineNumber){this.lineNumber = lineNumber;}public void getLineNumber(){return lineNumber;}/*public void myClose(){r.close();}*/}class MyLineNumberReaderDemo{public static void main(String[] args){FileReader fr = null;MyLineNumberReader mylnr = null;try{fr = new FileReader("copyText.java");mylnr = new MyLineNumberReader(fr);while((String line = mylnr.myReadLine()) != null){System.out.println(mylnr.getLineNumber()+":"+line);}}catch (IOException e){throw new IOException("读写失败！");}finally{try{if(mylnr != null)mylnr.myClose();}catch (IOException e){throw new IOException("读写失败！");}}}}/*eg:自定义字节流缓冲区包装类。*/import java.io.*;class MyBufferedInputStream{private InputStream in;private byte[] buffer = new byte[1024];private int pos = 0;private int count = 0;MyBufferedInputStream(InputStream in){this.in = in;}//一次读一个字节，从缓冲区(字节数组)获取。public int myRead() throws IOException{//通过in对象读取硬盘上数据，并存储buffer中if(count == 0){count = in.read(buffer);if(count < 0)return -1;pos = 0;byte b = buffer[pos];count --;pos ++;return b&255;}else if(count > 0){byte b = buffer[pos];count --;pos ++;return b;}return -1;}public void MyClose(){in.close();}}