Java program to convert decimal to binary

There are three following ways to convert Decimal number to binary number:

1) Using toBinaryString() method of Integer class.
2) Do conversion by writing your own logic without using any predefined methods.
3) Using Stack

Method 1: Using toBinaryString() method

class DecimalBinaryExample{
     
    public static void main(String a[]){
     System.out.println("Binary representation of 124: ");
     System.out.println(Integer.toBinaryString(124));
        System.out.println("\nBinary representation of 45: ");
        System.out.println(Integer.toBinaryString(45));
        System.out.println("\nBinary representation of 999: ");
        System.out.println(Integer.toBinaryString(999));
    }
}

Output:

Binary representation of 124: 
1111100

Binary representation of 45: 
101101

Binary representation of 999: 
1111100111

Method 2: Without using predefined method

class DecimalBinaryExample{
 
  public void convertBinary(int num){
     int binary[] = new int[40];
     int index = 0;
     while(num > 0){
       binary[index++] = num%2;
       num = num/2;
     }
     for(int i = index-1;i >= 0;i--){
       System.out.print(binary[i]);
     }
  }
 
  public static void main(String a[]){
     DecimalBinaryExample obj = new DecimalBinaryExample();
     System.out.println("Binary representation of 124: ");
     obj.convertBinary(124);
     System.out.println("\nBinary representation of 45: ");
     obj.convertBinary(45);
     System.out.println("\nBinary representation of 999: ");
     obj.convertBinary(999);
  }
}

Output:

Binary representation of 124: 
1111100
Binary representation of 45: 
101101
Binary representation of 999: 
1111100111

Method 3: Decimal to Binary using Stack

import java.util.*;
class DecimalBinaryStack
{
  public static void main(String[] args) 
  { 
    Scanner in = new Scanner(System.in);
 
    // Create Stack object
    Stack<Integer> stack = new Stack<Integer>();
 
    // User input 
    System.out.println("Enter decimal number: ");
    int num = in.nextInt();
 
    while (num != 0)
    {
      int d = num % 2;
      stack.push(d);
      num /= 2;
    } 
 
    System.out.print("\nBinary representation is:");
    while (!(stack.isEmpty() ))
    {
      System.out.print(stack.pop());
    }
    System.out.println();
  }
}

Output:

Enter decimal number: 
999

Binary representation is:1111100111