黑马程序员JAVA高级视频_IO输入与输出19天6(LineNumberReader与自定义LineNumberReader)

package string.test;

import java.io.BufferedWriter;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.LineNumberReader;
import java.io.Reader;

/*
 * LineNumberReader 
 *     跟踪行号的缓冲字符输入流。此类定义了方法 setLineNumber(int) 和 getLineNumber()，它们可分别用于设置和获取当前行号。
 */
public class LineNumberReaderDemo {
    public static void main(String[] args) throws IOException {
        FileWriter fw = new FileWriter("demo.txt");
        BufferedWriter bw = new BufferedWriter(fw);
        for (int i = 0; i < 100; i++) {
            bw.write("zhangsanailisi" + i);
            bw.newLine();
            bw.flush();
        }
        FileReader fr = new FileReader("demo.txt");
        //java提供的
        /*
         * LineNumberReader lbr = new LineNumberReader(fr); String line = null;
         * while ((line = lbr.readLine()) != null) {
         * 
         * System.out.println(lbr.getLineNumber() + "." + line); } bw.close();
         * lbr.close();
         */
        //自定义的MyLineNumberDemo
        MyLineNumberDemo mln = new MyLineNumberDemo(fr);
        String line = null;
        mln.setLineNumber(800);
        while ((line = mln.myReadLine()) != null) {
            System.out.println(mln.getLineNumber()+"." + line);
        }
        bw.close();
        mln.myClose();
    }
}
/*
 * 自定义的LineNumberReader
 * 
 */
class MyLineNumberDemo {
    private Reader r;
    private int lineNumber = 0;

    public MyLineNumberDemo(Reader r) {
        this.r = r;
    }

    public String myReadLine() throws IOException {
        lineNumber++;
        StringBuilder sb = new StringBuilder();
        int i = 0;
        while ((i = r.read()) != -1) {
            if (i == '\r')
                continue;
            if (i == '\n')
                return sb.toString();
            sb.append((char) i);
        }
        if (sb.length() != 0) {
            return sb.toString();
        }
        return null;
    }

    public void setLineNumber(int lineNumber) {
        this.lineNumber = lineNumber;
    }

    public int getLineNumber() {
        return lineNumber;
    }

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