java读写txt

新建项目 类

得到结构如下:

TestIo类中的代码:

package Test;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Calendar;

public class TestIo {

	private static final DateFormat DATE_FORMAT = new SimpleDateFormat(
			"yyyy-MM-dd");
	
	public static void writeToFile(String fileName, String content) {
		String time = DATE_FORMAT.format(Calendar.getInstance().getTime());
		
		File dirFile = null;
		try {
			dirFile = new File("e:\\" + time);
			if (!(dirFile.exists()) && !(dirFile.isDirectory())) {
				boolean creadok = dirFile.mkdirs();
				if (creadok) {
					System.out.println(" ok:创建文件夹成功！ ");
				} else {
					System.out.println(" err:创建文件夹失败！ ");
				}
			}
		} catch (Exception e) {
			e.printStackTrace();
		}
		String fullPath = dirFile + "/" + fileName + ".txt";
		write(fullPath, content);
	}

	/**
	 * 写文件
	 * 
	 * @param path
	 * @param content
	 */
	public static boolean write(String path, String content) {
		String s = new String();
		String s1 = new String();
		BufferedWriter output = null;
		try {
			File f = new File(path);
			if (f.exists()) {
			} else {
				System.out.println("文件不存在，正在创建...");
				if (f.createNewFile()) {
					System.out.println("文件创建成功！");
				} else {
					System.out.println("文件创建失败！");
				}
			}
			BufferedReader input = new BufferedReader(new FileReader(f));
			while ((s = input.readLine()) != null) {
				s1 += s + "\n";
			}
			System.out.println("原文件内容：" + s1);
			input.close();
			s1 += content;
			output = new BufferedWriter(new FileWriter(f));
			output.write(s1);
			output.flush();
			return true;
		} catch (Exception e) {
			e.printStackTrace();
			return false;
		} finally {
			if (output != null) {
				try {
					output.close();
				} catch (IOException e) {
					e.printStackTrace();
				}
			}
		}
	}
	
	
	
	public static String readFile(String str) {
		File file = new File(str);
		String line;
		InputStreamReader isr= null;
		try {
			isr = new InputStreamReader(new FileInputStream(file), "utf-8");  
			BufferedReader in = new BufferedReader(isr);// 包装文件输入流，可整行读取
			StringBuilder sb = new StringBuilder();
			while ((line = in.readLine()) != null) {
				sb.append(line);
				
			}
			return sb.toString();
		} catch (FileNotFoundException e) {
			e.printStackTrace();
			return null;
		}// 创建文件输入流
		catch (IOException e) {
			e.printStackTrace();
			return null;
		} finally {
			if (isr != null) {
				try {
					isr.close();
				} catch (IOException e) {
					e.printStackTrace();
				}
			}
		}
	}
	
	
	public static void main(String[] args) {
		
	String	fileName ="test";
	String content="Tonight,we are young";
		
		writeToFile(fileName, content);
		
//	String ReadString=	readFile("e:/2013-09-11/test.txt");
//		System.out.print(ReadString);
	}
}

先写入:

显示结果:

而且在e盘中已经生成了 文件:

内容如下:

程序读取显示如下:

PS:需要换行时 在字符串后加上"\r\n'