code: package com.fdu.se.sootanalyze.utils;
  
  import java.io.BufferedWriter;
  import java.io.File;
  import java.io.FileWriter;
  import java.io.IOException;
  import java.util.ArrayList;
  import java.util.List;
  
  public class FileUtil {
      public static List<String> getApkPaths(String path){
          List<String> apkPaths = new ArrayList<>();
          File apkDir = new File(path);
          File[] files = apkDir.listFiles();
          for(File f:files){
              if(f.isFile() && f.getName().endsWith(".apk")){
                  String apkPath = f.getAbsolutePath();
                  apkPaths.add(apkPath);
              }
          }
          return apkPaths;
      }
  
      public static void filePrintln(String fileName, String content){
          try{
              BufferedWriter out=new BufferedWriter(new FileWriter(fileName,true));
              out.write(content);
              out.newLine();
              out.close();
          }catch (IOException e) {
              e.printStackTrace();
          }
      }
  
      public static void main(String[] args) {
          List<String> apkPaths = getApkPaths("E:\\E backup\\AndroidTesting\\test app\\APP1");
          for(String apkPath:apkPaths){
              System.out.println(apkPath);
          }
      }
  }
  