您必须使用从原始文件逐行读取它的方法。搜索并用新号码替换薪水。将内容写入新的临时文件。删除原始文件。最后将临时文件替换为原始文件名。这是执行此操作的代码：
import java.io.BufferedReader;import java.io.File;import java.io.FileReader;import java.io.FileWriter;import java.io.IOException;import java.io.PrintWriter;import java.util.Scanner;public class FileContentUpdater { public static void main(String args[]) throws IOException { String ID, Name; double salary; int replenish; Scanner console = new Scanner(System.in); System.out.print("Enter ID : "); String pID = console.nextLine(); System.out.print("Enter replenish salary: "); replenish = console.nextInt(); File originalFile = new File("file.txt"); BufferedReader br = new BufferedReader(new FileReader(originalFile)); // Construct the new file that will later be renamed to the original // filename. File tempFile = new File("tempfile.txt"); PrintWriter pw = new PrintWriter(new FileWriter(tempFile)); String line = null; // Read from the original file and write to the new // unless content matches data to be removed. while ((line = br.readLine()) != null) { if (line.contains(pID)) { String strCurrentSalary = line.substring(line.lastIndexOf(" "), line.length()); if (strCurrentSalary != null || !strCurrentSalary.trim().isEmpty()) { int replenishedSalary = Integer.parseInt(strCurrentSalary.trim()) + replenish; System.out.println("replenishedSalary : " + replenishedSalary); line = line.substring(0,line.lastIndexOf(" ")) + replenishedSalary; } } pw.println(line); pw.flush(); } pw.close(); br.close(); // Delete the original file if (!originalFile.delete()) { System.out.println("Could not delete file"); return; } // Rename the new file to the filename the original file had. if (!tempFile.renameTo(originalFile)) System.out.println("Could not rename file"); }}
