自制MyLineNumberReader

import java.io.*;
class MyBufferedReader extends Reader
{
private Reader r;//全局使用
MyBufferedReader(Reader r)
{
this.r = r;
}
public String myReadLine()throws IOException//一次读一行
{
//StringBuilder
StringBuilder sb = new StringBuilder();
int ch = 0;
while ((ch=r.read())!=-1){
if(ch=='\r')
continue;

if(ch=='\n')
return sb.toString();
else
sb.append((char)ch);
}
return null;
}
public int read(char[] cbuf, int off, int len) //抽象类必须被复写
{
return read(cbuf,off, len);
}

public void close()throws IOException
{
r.close();
}

public void myClose()throws IOException
{
r.close();
}
}

class MyBufferedReaderDemo{
public static void main(String[] args) throws IOException
{
FileReader fr = new FileReader("buf.txt");
MyBufferedReader mybuf = new MyBufferedReader(fr);
String line = null;
while((line=mybuf.myReadLine())!=null){
System.out.println(line);
}
mybuf.myClose();

}
}

 

使用已经写好的类

import java.io.*;

/*class MyLineNumberReader 
{
private Reader r;

MyLineNumberReader(Reader r)
{
this.r=r;
}
private int num=0;
//private BufferedReader buf;
//buf = new BufferedReader(r);
public int myGetLineNumber(){
return num;
}
public void mySetNumber(int num)
{
this.num=num;
}
public String myReadLine()throws IOException
{
num++;
StringBuilder sb = new StringBuilder();
int ch = 0;
while ((ch=r.read())!=-1){
if(ch=='\r')
continue;

if(ch=='\n')
return sb.toString();
else
sb.append((char)ch);
}
return null;
}
public int read(char[] cbuf, int off, int len) 
{
return read(cbuf,off, len);
}

public void close()throws IOException
{
r.close();
}
}*/
class MyLineNumberReader extends MyBufferedReader
{    
private int num=0;
MyLineNumberReader(Reader r){
super(r);
}
public String myReadLine()throws IOException
{
num++;
return super.myReadLine();
}
public int myGetLineNumber(){
return num;
}
public void mySetNumber(int num)
{
this.num=num;
}

}

class MyLineNumberReaderDemo
{
public static void main(String[] args)throws IOException
{
FileReader fr = new FileReader("MyBufferedReaderDemo.java");
MyLineNumberReader mlnr= new MyLineNumberReader(fr);
String str = null;
mlnr.mySetNumber(100);
while((str=mlnr.myReadLine())!=null)
{
System.out.println(mlnr.myGetLineNumber()+":"+str);
}
mlnr.close();
}
}