我就廢話不多說了，大家還是直接看代碼吧~

import java.io.File;import java.io.FileWriter;import java.io.IOException;public class FileWriterUtil { /** * 追加文件：使用FileWriter */ public static void appendMethod(String fileName, String content) {try { //打開一個寫文件器，構(gòu)造函數(shù)中的第二個參數(shù)true表示以追加形式寫文件 FileWriter writer = new FileWriter(fileName, true); writer.write(content); writer.close();} catch (IOException e) { e.printStackTrace();} } /** * 修改文件名 * @param oldFilePath * @param newFileName */ public static void reNameLogFile(String oldFilePath,String newFileName){File f=new File(oldFilePath);String c=f.getParent();//File mm=new File(c + File.pathSeparator + newFileName + '_' + CommonUtil.getCurrTimeForString());File mm=new File(c + '/' + newFileName + '_' + CommonUtil.getBeforeDateStr());if(f.renameTo(mm)){ System.out.println('修改文件名成功!');}else{ System.out.println('修改文件名失敗');} } public static void main(String[] args) {String fileName = '/Users/qin/Downloads/callLog.txt';String content = 'new append!';FileWriterUtil.appendMethod(fileName, content);FileWriterUtil.appendMethod(fileName, 'append end. n');FileWriterUtil.reNameLogFile('/Users/qin/Downloads/callLog.txt','rayda'); }}Java PrintWriter&FileWriter 寫入追加到文件用PrintWriter寫入文件

import java.io.IOException;import java.io.PrintWriter;public class PrintWriteDemo{ public static void main(String[] args) throws IOException {PrintWriter out = new PrintWriter('01.txt');out.print('the quick brown fox');out.println(' jumps over the lazy dog.');out.write('work is like a capricious lover whose ');out.write('incessant demands are resented but who is missed terribly when she is not theren');out.close(); //如果不關(guān)閉文件，文件停留在buffer zone, 不會寫進(jìn)'01.txt'中 }}

FileWriter只能寫入文件，無法往文件中追加內(nèi)容

import java.io.IOException;import java.io.FileWriter;public class FileWriterDemo{ public static void main(String[] args) throws IOException {FileWriter out = new FileWriter('02.txt');//constructor中添加true,即FileWriter out = new FileWriter('02.txt', true)就是往02.txt中追加文件了out.write('work is like a capricious lover whose ');out.write('incessant demands are resented but who is missed terribly when she is not theren');out.write(98.7 + 'n');out.close(); //很重要，一定記得關(guān)閉文件 }}

都別忘記 throws IOException

以上為個人經(jīng)驗，希望能給大家一個參考，也希望大家多多支持好吧啦網(wǎng)。