Java写txt—读txt—清空txt文件

Java操作txt文件读、写、清空

1. 需求2. 解决方案2.1 写txt2.2 读txt2.2.1 一行一行的读取返回ArrayList集合2.2.2 一次性读取所有返回字符串2.3 清空txt中的内容2.4 所有代码

1. 需求

任务提交完成后会生成一个办件号，然后后台审核（大概是十几分钟）审核完毕后要操作查询（通过办件号查询）

所以说上一个任务生成的办件号需要保存起来，，，后边查询任务需要使用

这里考虑用txt文本存储

2. 解决方案

👍 创建一个txt，操作txt的读取和写入

2.1 写txt

👍 不覆盖的写

👍 FileWriter(file,true)，true 表示可以将数据写入文件的末尾而不会替换文件原来的内容

package com.guo.Util;import java.io.*;public class WriteTxt {public static void writeFile(String data){try{String filePath = "C:\\Users\\EDY\\Desktop\\write.txt";File file =new File(filePath);//如果文件不存在则创建if(!file.exists()){file.createNewFile();}//FileWriter(file,true)，true 表示可以将数据写入文件的末尾而不会替换文件原来的内容FileWriter fileWritter = new FileWriter(file,true);BufferedWriter bufferWritter = new BufferedWriter(fileWritter);bufferWritter.write(data);//bufferWritter.write("\n");bufferWritter.close();System.out.println("写入成功");}catch(IOException e){e.printStackTrace();}}public static void main( String[] args ) {StringBuilder data = new StringBuilder();data.append("123456").append("\n");data.append("234567").append("\n");data.append("345678").append("\n");writeFile(data.toString());}}

2.2 读txt

2.2.1 一行一行的读取返回ArrayList集合

👍 以行为单位读取文件内容，一次读一整行，读取的内容放在ArrayList集合中，方便后续按行操作数据。

package com.guo.Util;import java.io.*;import java.util.ArrayList;import static com.guo.Util.WriteTxt.writeFile;public class ReadTxt {public static ArrayList readFile(){File file = new File("C:\\Users\\EDY\\Desktop\\write.txt");BufferedReader reader = null;String tempString = null;ArrayList<String> stringLists = new ArrayList<>();try {System.out.println("以行为单位读取文件内容，一次读一整行：");reader = new BufferedReader(new FileReader(file));while ((tempString = reader.readLine()) != null) {stringLists.add(tempString);}reader.close();} catch (FileNotFoundException e) {e.printStackTrace();} catch (IOException e) {e.printStackTrace();}finally{if(reader != null){try {reader.close();} catch (IOException e) {e.printStackTrace();}}}return stringLists;}public static void main(String[] args) {ArrayList<String> list = readFile(); //取出数据for (int i = 0; i < list.size(); i++) {System.out.println(list.get(i));}clearInfoForFile(); //清除文件中所有的内容//取出的数据做特殊的处理for (int i = 0; i < list.size(); i++) {if (list.get(i).contains(",")||"".equals(list.get(i))){list.remove(i);i--;}}StringBuilder sB = new StringBuilder();for (int i = 0; i < list.size(); i++) {if (!"0".equals(list.get(i))||"\n".equals(list.get(i))){//如果这一行没有被标记0，就添加到SB字符串中sB.append(list.get(i)).append("\n"); //每条数据单独占一行，方便取数据}}writeFile(sB.toString());System.out.println(sB);}//清空txt文件public static void clearInfoForFile() {File file = new File("C:\\Users\\EDY\\Desktop\\write.txt");try {if(!file.exists()) {file.createNewFile();}FileWriter fileWriter =new FileWriter(file);fileWriter.write("");fileWriter.flush();fileWriter.close();} catch (IOException e) {e.printStackTrace();}}}

2.2.2 一次性读取所有返回字符串

👍 以文件内容为单位一次性读取所有内容，并放在字符串中返回。

public static String readToString() {String fileName = "C:\\Users\\EDY\\Desktop\\input.txt";String encoding = "UTF-8";File file = new File(fileName);Long filelength = file.length();byte[] filecontent = new byte[filelength.intValue()];try {FileInputStream in = new FileInputStream(file);in.read(filecontent);in.close();} catch (FileNotFoundException e) {e.printStackTrace();} catch (IOException e) {e.printStackTrace();}try {return new String(filecontent, encoding);} catch (UnsupportedEncodingException e) {System.err.println("The OS does not support " + encoding);e.printStackTrace();return null;}}

2.3 清空txt中的内容

👍 这里用的是覆盖的写txt

👍 FileWriter(file,true)，true 表示末尾追加新数据

👍 FileWriter(file)，表示新的数据覆盖原来的所有的数据

//清空txt文件public static void clearInfoForFile() {File file = new File("C:\\Users\\EDY\\Desktop\\write.txt");try {if(!file.exists()) {file.createNewFile();}FileWriter fileWriter =new FileWriter(file);fileWriter.write(""); //写入空fileWriter.flush();fileWriter.close();} catch (IOException e) {e.printStackTrace();}}

2.4 所有代码

🤭 这里的文件的路径名称写死的可以根据情况自定义修改

public static void writeFile(String data){try{String filePath = "C:\\Users\\EDY\\Desktop\\good.txt";File file =new File(filePath);//如果文件不存在则创建if(!file.exists()){file.createNewFile();}//FileWriter(file,true)，true 表示可以将数据写入文件的末尾而不会替换文件原来的内容FileWriter fileWritter = new FileWriter(file,true);BufferedWriter bufferWritter = new BufferedWriter(fileWritter);bufferWritter.write(data);//bufferWritter.write("\n");bufferWritter.close();System.out.println("写入成功");}catch(IOException e){e.printStackTrace();}}public static ArrayList readFile(){File file = new File("C:\\Users\\EDY\\Desktop\\good.txt");BufferedReader reader = null;String tempString = null;ArrayList<String> stringLists = new ArrayList<>();try {System.out.println("以行为单位读取文件内容，一次读一整行：");reader = new BufferedReader(new FileReader(file));while ((tempString = reader.readLine()) != null) {stringLists.add(tempString);}reader.close();} catch (FileNotFoundException e) {e.printStackTrace();} catch (IOException e) {e.printStackTrace();}finally{if(reader != null){try {reader.close();} catch (IOException e) {e.printStackTrace();}}}return stringLists;}public static void clearInfoForFile() {File file = new File("C:\\Users\\EDY\\Desktop\\good.txt");try {if(!file.exists()) {file.createNewFile();}FileWriter fileWriter =new FileWriter(file);fileWriter.write("");fileWriter.flush();fileWriter.close();} catch (IOException e) {e.printStackTrace();}}public static void main(String[] args) {ArrayList<String> list = readFile(); //读取数据for (int i = 0; i < list.size(); i++) {System.out.println(list.get(i));}clearInfoForFile(); //清除文件中所有的内容//取出的数据做特殊的处理for (int i = 0; i < list.size(); i++) {if (list.get(i).contains(",")||"".equals(list.get(i))){list.remove(i);i--;}}StringBuilder sB = new StringBuilder();for (int i = 0; i < list.size(); i++) {if (!"0".equals(list.get(i))||"\n".equals(list.get(i))){//如果这一行没有被标记0，就添加到SB字符串中sB.append(list.get(i)).append("\n"); //每条数据单独占一行，方便取数据}}writeFile(sB.toString()); //写数据System.out.println(sB);}// // public static void main( String[] args ) { //添加（写）数据// StringBuilder data = new StringBuilder();// data.append("123456").append("\n");// data.append("234567").append("\n");// data.append("345678").append("\n");// writeFile(data.toString());// }