IO流_自定义类模拟LineNumberReader的获取行号功能案例

最新推荐文章于 2024-09-16 17:09:24 发布

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最新推荐文章于 2024-09-16 17:09:24 发布

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分类专栏： Java IO File OutputStreamWriter InputStreamReader

本文链接：https://blog.youkuaiyun.com/L1585931143/article/details/56530211

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本文介绍了一个自定义的行号读取器类MyLineNumberReader及其测试方法。该类继承自MyBufferedReader，用于逐行读取文件，并记录当前行号。通过覆盖父类的readLine方法来实现按行读取文件内容的功能。

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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();
	}
}