Java program to convert decimal number to binary

Let’s learn java program to convert decimal number to binary.

java program to convert decimal number to binary

Java program to convert decimal number to binary

I’m going to show you how exactly decimal number 20 is converted to binary. In the below example we will be using Scanner class in java.util package. So you have number 20 divide that by 2 you get quotient 10 and remainder 0.

Now at this point we get one binary digit, that is 0 as the remainder. Remember the remainder is what gives you the binary digit. Now take quotient 10 again divide that by 2 and you get the quotient as 5 and remainder as 0.

Again take quotient 5. Divide that by 2 you will get the quotient as 2 and remainder as 1. Repeat the same procedure divide that by 2, you will get quotient as 1 and remainder as 0.

Now in the last step quotient is 1 and remainder is 1. Now, collecting all the remainders, you get 00101. Actually this is not the binary number.

We have to read reverse, that is, 10100 (we have to read it from right to left). Here’s the java program,

public class DecimalToBinaryDemo
   // function to convert decimal to binary
   static void toBinary(int num) 
      // here we are storing binary number 
      int binaryNumber[] = new int[1000]; 
      // "count" variable is counter for binary array 
      int count = 0; 
      while(num > 0)  
         // storing remainder in binary array 
         binaryNumber[count] = num % 2; 
         num = num / 2; 
      // here we are printing binary in reverse order 
      for(int a = count - 1; a >= 0; a--) 
   public static void main(String[] args)
      int number = 20; 



Also read – multidimensional array in java