Java 创建txt文件与读写内容

package com.broadtext.eim.test;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;

/**
 * 
 * TODO 此处为类的功能性说明
 * @Time 下午06:28:41
 * @author mengjiahao
 */
public class WriteTextService {
	public static BufferedReader bufread;

	// 指定文件路径和名称
	private static String path = "D:/sessionId.txt";

	private static File filename = new File(path);

	private static String readStr = "";

	/** */
	/**
	 * 创建文本文件.
	 * 
	 * @throws IOException
	 * 
	 */
	public static void creatTxtFile() throws IOException {
		if (!filename.exists()) {
			filename.createNewFile();
			System.err.println(filename + "已创建！");
		}
	}

	/** */
	/**
	 * 读取文本文件.
	 * 
	 * @throws IOException
	 * 
	 */
	public static String readTxtFile() throws IOException {
		String strs = "";
		try {
			FileReader read = new FileReader(filename);
			StringBuffer sb = new StringBuffer();
			char ch[] = new char[1024];
			int d = read.read(ch);
			while (d != -1) {
				String str = new String(ch, 0, d);
				sb.append(str);
				d = read.read(ch);
			}

			strs = sb.toString();
		} catch (FileNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		System.out.println("文件内容是:" + "\r\n" + strs);
		return strs;
	}

	/** */
	/**
	 * 写文件.
	 * 
	 */
	public static void writeTxtFile(String newStr) throws IOException {

		// 创建文件
		creatTxtFile();
		// 读取文件
		String str = readTxtFile();
		// 写入文件
		
		FileWriter fw = new FileWriter(path);
		if (str.length() < 1) {
			fw.write(newStr);
		} else {
			fw.write(str + "\r\n" + newStr);
		}
		fw.close();
	}

	/** */
	/**
	 * 将文件中指定内容的第一行替换为其它内容.
	 * 
	 * @param oldStr
	 *            查找内容
	 * @param replaceStr
	 *            替换内容
	 */
	public static void replaceTxtByStr(String oldStr, String replaceStr) {
		String temp = "";
		try {
			File file = new File(path);
			FileInputStream fis = new FileInputStream(file);
			InputStreamReader isr = new InputStreamReader(fis);
			BufferedReader br = new BufferedReader(isr);
			StringBuffer buf = new StringBuffer();

			// 保存该行前面的内容
			for (int j = 1; (temp = br.readLine()) != null
					&& !temp.equals(oldStr); j++) {
				buf = buf.append(temp);
				buf = buf.append(System.getProperty("line.separator"));
			}

			// 将内容插入
			buf = buf.append(replaceStr);

			// 保存该行后面的内容
			while ((temp = br.readLine()) != null) {
				buf = buf.append(System.getProperty("line.separator"));
				buf = buf.append(temp);
			}

			br.close();
			FileOutputStream fos = new FileOutputStream(file);
			PrintWriter pw = new PrintWriter(fos);
			pw.write(buf.toString().toCharArray());
			pw.flush();
			pw.close();
		} catch (IOException e) {
			e.printStackTrace();
		}
	}

	/** */
	/**
	 * main方法测试
	 * 
	 * @param s
	 * @throws IOException
	 */
	public static void main(String[] s) throws IOException {
		// 创建文件
		creatTxtFile();
		// 读取文件
		readTxtFile();
		// 写入文件
		writeTxtFile("道是无晴却有晴");
		// 读取文件
		readTxtFile();

	}

}