IO流_自定义类模拟LineNumberReader的获取行号功能案例

package cn.itcast_09;

import java.io.IOException;
import java.io.Reader;

public class MyLineNumberReader {
  private Reader r;
  private int lineNumber = 0;

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

  public int getLineNumber() {
    return lineNumber;
  }

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

  public String readLine() throws IOException {
    lineNumber++;

    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);
      }
    }

    if (sb.length() > 0) {
      return sb.toString();
    }

    return null;
  }

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

package cn.itcast_09;

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

/*
 * 测试MyLineNumberReader类
 */
public class MyLineNumberReaderTest {
  public static void main(String[] args) throws IOException {
    // MyLineNumberReader mlnr = new MyLineNumberReader(new FileReader(
    // "my.txt"));
    MyLineNumberReader2 mlnr = new MyLineNumberReader2(new FileReader(
        "my.txt"));

    // mlnr.setLineNumber(10);

    String line = null;
    while ((line = mlnr.readLine()) != null) {
      System.out.println(mlnr.getLineNumber() + ":" + line);
    }

    // 释放资源
    mlnr.close();
  }
}

终级代码

package cn.itcast_09;

import java.io.IOException;
import java.io.Reader;

import cn.itcast_08.MyBufferedReader;

public class MyLineNumberReader2 extends MyBufferedReader {
  private Reader r;
  private int lineNumber = 0;

  public MyLineNumberReader2(Reader r) {
    super(r);
  }

  public int getLineNumber() {
    return lineNumber;
  }

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

  @Override
  public String readLine() throws IOException {
    lineNumber++;
    return super.readLine();
  }
}