Search and replace a word or phrase in a list of files under a directory Using Java

Search and replace a word or phrase in a list of files under a directory Using Java

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.Scanner;

public class SearchNReplace {
 static String extension;
 static String find;
 static String replace;
 static int i;

 public static void writefiles(File g, String find, String replace)
   throws IOException {
  File li[] = g.listFiles();
  for (int j = 0; j < li.length; j++) {
   System.out.println(li[j].getName());
   if (li[j].isDirectory()) {
    writefiles(li[j], find, replace);
   } else if (li[j].isFile() && li[j].getName().endsWith(extension)) {

    InputStream f = new FileInputStream(li[j]);
    int n = f.available();
    byte b[] = new byte[n];
    f.read(b);
    String str = new String(b, 0, n);
    System.out.println(str);
    String repl = str.replaceAll(find, replace);
    System.out.println(repl);
    byte[] wr = repl.getBytes();
    f.close();
    if (!repl.equals(str)) {
     OutputStream o = new FileOutputStream(li[j]);
     o.write(wr);
     o.close();
    }
   }
  }
 }

 public static void main(String args[]) throws IOException {
  Scanner scan = new Scanner(System.in);
  System.out.println("Enter the directory path");
  String dirname = scan.nextLine();

  File f1 = new File(dirname);
  if (f1.exists()) {
   if (f1.length() == 0) {
    System.out.println("No files exist in the directory");
   } else {
    System.out.println("Enter the extension");
    String extension = scan.nextLine();
    File[] s = f1.listFiles();

    //boolean name = s[i].getName().endsWith(extension);
    //if (name == false) {
    for (int i = 0; i < s.length; i++) {
    if(!s[i].getName().endsWith(extension)){
     
     System.out.println(s[i].getName() + ": Invalid extension ");
    } else {

     //System.out.println(s[i].getName().endsWith(extension));

     //for (int i = 0; i < s.length; i++) {

      System.out.println(s[i].getName());
      System.out.println("Enter the word to find");
      String find = scan.nextLine();
      InputStream f = new FileInputStream(s[i]);
      int n = f.available();
      byte b[] = new byte[n];
      f.read(b);
      String str = new String(b, 0, n);
      System.out.println(str);
      if(!str.contains(find))
      {
      System.out.println("No such word Exist");
      }
      else
      {
    
       
       System.out.println("Enter the word to replace");
       String replace = scan.nextLine();

       if (s[i].isDirectory() && !s[i].isHidden()) {
        writefiles(s[i], find, replace);
       } else if (s[i].isFile()
         && s[i].getName().endsWith(extension)) {

        System.out.println(s[i].getName());
        InputStream f2 = new FileInputStream(s[i]);
        int n1 = f2.available();
        byte b1[] = new byte[n1];
        f2.read(b1);
        String str1 = new String(b1, 0, n1);
        System.out.println(str1);
       
        String repl = str1.replaceAll(find, replace);
        System.out.println(repl);
        byte[] wr = repl.getBytes();
        f2.close();
        if (!repl.equals(str1)) {
         OutputStream o = new FileOutputStream(s[i]);
         o.write(wr);
         o.close();
        }
       }
      }
      }
     }
    }
  }
   else {
   System.out.println("Folder does not exist.");
  }
 }
}