import java.io.*; import java.util.*; public class Test {     public static void main(String[] args) throws IOException {         BufferedReader br = new BufferedReader(new FileReader("output1.txt"));         List<String> newName = new ArrayList<String>();         List<String> oldName = new ArrayList<String>();         String line;         String[] col;         while((line=br.readLine())!=null) {             col = line.split("#");             newName.add(col[0]);             oldName.add(col[1]);         }         br.close();         for(int i=0;i<newName.size();i++) {             File oldFile = new File("D:\\TDDOWNLOAD\\heihei\\"+oldName.get(i)+".mp4");             System.out.println(oldFile.exists());//看文件是否存在             File newFile = new File(oldFile.getParent()+File.separator+newName.get(i)+".mp4");             if(newFile.exists()) {                 System.out.println(i+"已存在");//新文件已存在             } else {                 System.out.println(i+"\t"+oldFile.renameTo(newFile));//旧文件是否重命名成功             }         }     } }