Generate all binary numbers in range [L, R] with same length

// Java code to implement the approach
import java.util.*;
public class GFG
{

  // Function to convert a number to binary
  static ArrayList<Integer> convertToBinary(int num, 
                                            int length)
  {
    ArrayList<Integer> bits= new ArrayList<Integer>();
    for(int i = 0; i < length; i++) {
      bits.add(0);
    }
    if (num == 0) {
      return bits;
    }

    int i = length - 1;
    while (num != 0) {
      bits.set(i, (num % 2));
      i = i - 1;

      // Integer division
      // gives quotient
      num = num / 2;
    }

    return bits;
  }

  // Function to convert all numbers 
  // in range [L, R] to binary of 
  // same length
  static ArrayList<ArrayList<Integer> > getAllBinary(int l, 
                                                     int r)
  {

    // Length of the binary numbers
    double x = Math.log(r+1);
    double y = Math.log (2);
    int n = (int) Math.ceil(x / y);

    ArrayList<ArrayList<Integer> > binary_nos = 
      new ArrayList<ArrayList<Integer> >();

    for (int i = l; i <= r; i++) {
      ArrayList<Integer> bits = 
        convertToBinary(i, n);
      binary_nos.add(bits);
    }

    return binary_nos;
  }

  // Driver code
  public static void main(String args[])
  {
    int L = 2, R = 8;
    ArrayList<ArrayList<Integer> > binary_nos =
      getAllBinary(L, R);
    for (int i = 0; i < binary_nos.size(); i++) {
      for (int j = 0; j < binary_nos.get(i).size(); j++) {
        System.out.print(binary_nos.get(i).get(j));
      }
      System.out.println();
    }
  }
}

// This code is contributed by Samim Hossain Mondal.