Java Program:

Example:

import java.util.Scanner;
public class CheckBinary {
  public static boolean binary(long num) {
    while(num!=0) {
      if(num%10==0 || num%10==1)
        num/=10;
      else return false;
    }
    return true;
  }

  public static void main(String []args) {
    long num;
    Scanner userInput = new Scanner(System.in);
    System.out.print("Enter your number : ");
    num = userInput.nextLong();

    if(binary(num))
      System.out.println("Number is in binary form");
    else 
      System.out.println("Number is not in binary form");
  }
}

Output:

  Enter Your number : 1101
  Number is in binary form

Binary Numbers : Numbers with only 0 & 1 combination

Examples like: 101, 111, 10, 11111

Main Logic :

public static int binary(long num) {
  while(num!=0) {
    if(num%10==0 || num%10==1)
      num/=10;
    else return false;
  }
  return true;
}

Divide the number by 10 while your number becomes 0[ZERO] &
In-between check, is there any remainder other than 0 & 1