JAVA之IO技术-自定义的LineNumberReader类

package ioTest.io2;
/*
 * 自定义一个带有读取行号方法的读取文件的装饰类
 */
import java.io.FileReader;
import java.io.IOException;
import java.io.Reader;

public class MyLineNumberReaderDemo {

	public static void main(String[] args) throws IOException {
		String line;
		//创建输入流-读取文件信息到流中区，所以对于流来讲是“入”了
		FileReader in=new FileReader("BufferedWriterDemo.java");
		MyLineNumberReader mlnr=new MyLineNumberReader(in);
		while((line=mlnr.MyReadLine())!=null)
		{
			System.out.println(mlnr.getLineNumber()+":"+line);
		}
		mlnr.close();
	}

}
//定义一个自定义的类似于LineNumberReader的类
class  MyLineNumberReader extends Reader{
	private Reader r;
	int lineNumber;
	int ch=0;
	String line=null;
	//根据构造函数判断，显然此类也是一个构造类
	MyLineNumberReader(Reader r)
	{
		this.r=r;
	}
	public String MyReadLine() throws IOException {
		lineNumber++;
		StringBuilder sBuilder=new StringBuilder();
		while((ch=r.read())!=-1)
		{
			if(ch=='\n')
				continue;
			if(ch=='\r')
				return sBuilder.toString();
			else
				sBuilder.append((char)ch);
		}
		if(sBuilder.length()>





0)
			return sBuilder.toString();
		return null;
	}
	
	public int getLineNumber() {
		return lineNumber;
	}
	public void setLineNumber(int lineNumber) {
		this.lineNumber = lineNumber;
	}
	@Override
	public int read(char[] cbuf, int off, int len) throws IOException {
		// TODO Auto-generated method stub
		return 0;
	}
	@Override
	public void close() throws IOException {
		// TODO Auto-generated method stub
		r.close();
	}
}