黑马程序员JAVA高级视频_IO输入与输出19天4(MyBufferedReader)

package itcast.java16;

import java.io.FileReader;
import java.io.IOException;

/*
 * 
 * 自定义readLine();
 */
class MyBufferedReader {
    private FileReader fr;

    public MyBufferedReader(FileReader fr) {
        this.fr = fr;
    }

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

    public void myClose() throws IOException {
        if (fr != null) {
            fr.close();
        }
    }
}

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