convert a decimal number into binary in java code example

Example 1: Convert decimal number to binary in java without using array

public class DecimalToBinaryWithoutArray
{
   static void toBinary(int num)
   { 
      StringBuilder sb = new StringBuilder(); 
      int a = 0;
      while(num > 0)
      {
         sb.append(num % 2);
         a++;
         num = num / 2;
      }
      System.out.println(sb.reverse()); 
   }
   public static void main(String[] args) 
   {
      int number = 20; 
      toBinary(number);
   }
}

Example 2: convert decimal to binary in java

public class DecimalToBinaryExample2{    
public static void toBinary(int decimal){    
     int binary[] = new int[40];    
     int index = 0;    
     while(decimal > 0){    
       binary[index++] = decimal%2;    
       decimal = decimal/2;    
     }    
     for(int i = index-1;i >= 0;i--){    
       System.out.print(binary[i]);    
     }    
System.out.println();//new line  
}    
public static void main(String args[]){      
System.out.println("Decimal of 10 is: ");  
toBinary(10);    
System.out.println("Decimal of 21 is: ");  
toBinary(21);    
System.out.println("Decimal of 31 is: ");    
toBinary(31);  
}}