java继承与组合 - 黑马程序员技术交流社区

/*装饰者设计模式与继承的比较
MyReader//专门用于读取数据-----继承的结构
|--MyTextReader
|--MyBufferTextReader
|--MyMediaReader
|--MyBufferMediaReader
|--MyDataReader
|--MyBufferDataReader
class MyBufferReader
{
MyBufferReader(MyTextReader text){
}
MyBufferReader(MyMediaReader text){
}
MyBufferReader(MyDataReader text){
}
}
该类的扩展性很差，
找到其参数的共同类型，通过多态形式通过扩展性
class MyBufferReader extends MyReader //继承公共父类，即MyReader，而不像继承结构中-继承MyReader的子类
{
MyBufferReader(MyReader r){
}
}
MyReader//专门用于读取数据的类-----装饰模式的结构
|--MyTextReader
|--MyMediaReader
|--MyDataReader
|--MyBufferReader //组合结构
*/
import java.io.*;
class MyBufferedReader extends Reader
{
private Reader fr = null;
MyBufferedReader(Reader fr){
this.fr = fr;
}
public String myReadLine() throws IOException{
StringBuilder sb = new StringBuilder(); //StringBuilder();
int ch = 0;
while ((ch = fr.read())!= -1)
{
if (ch=='\r')
continue; // the keyword continue.
if(ch == '\n')
return sb.toString();
sb.append((char)ch);
}
if (sb.length() != 0)
return sb.toString(); //important to return the last line.
return null;
}
public int read (char[] buf, int off, int len) throws IOException{
return read (buf, off, len); //调用对象方法
}
public void close() throws IOException{
fr.close(); //调用对象方法
}
public void myClose() throws IOException{
fr.close();
}
}
class MyBufferedReaderDemo{
public static void main(String[] args) throws IOException
{
FileReader fr = new FileReader("buf.txt");
MyBufferedReader mr = new MyBufferedReader(fr);
String line = null;
while ((line = mr.myReadLine()) != null)
{
System.out.println(line);
}
System.out.println("Hello World!");
}
}

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