Program to Convert Decimal to Binary in Java

The Java program simply converts a decimal number to binary. In computing, a decimal number is a number system having a base of 10 ( 0 to 9), whereas a binary number having a base of 2 ( 0 or 1).

There are 3 following ways to convert a Decimal to Binary in Java :

1. With the predefined method
2. Without the predefined method
3. Using recursion

1. Program to convert decimal to binary in Java using without predefined method

Program:

import java.util.Scanner;

public class DecimalToBinary {

    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        int decimal, tmpDecimal;
        int binary[] = new int[20];
        int i = 0;
        System.out.print("Please enter a decimal number = ");
        decimal = input.nextInt();
        tmpDecimal = decimal;
// While decimal number isn't equal to zero, do
        while (tmpDecimal != 0) {
            binary[i] = tmpDecimal % 2; // storing remainder in array named binary
// Storing quotient within decimal variable itself, so that it shrinks down to 0
            tmpDecimal = tmpDecimal / 2;
            i = i + 1;
        }
// Printing array having binary numbers in reverse order
        System.out.print("\n Decimal number = " + decimal + "\n Binary Number= ");
        while (i >= 0) {
            System.out.print(binary[i]);
            i = i - 1;
        }
        System.out.print("\n");
    }
}

Output:

Please enter a decimal number = 79

 Decimal number = 79
 Binary Number= 01001111

Explanation:

• In the above code, first, we got a decimal input from the user and assigned it to ‘tempDecimal’ variable
• Afterwards, we were iterating through the loop till “tempDecimal” value became 0
• In the loop body, we were converting the input to binary by dividing it by 2 and storing its remainder to binary[] array and updating the tempDecimal with quotient on each iteration.
• Lastly, we reversed the array and printed as output

2. Program to convert decimal to binary in Java using with a predefined method.

• In this, a built-in method named toBinaryString() is used for the conversion
• It comes under Integer class and takes an integer value as an argument
• It is a static method

Program : 

public class DecimalToBinary {
    public static void main(String[] args) {
        int decimalNum = 79;
        System.out.println(" Decimal to Binary Value : " + Integer.toBinaryString(decimalNum));
    }
}

Output:

Decimal to Binary Value : 1001111

Explanation:

In above code,  we used toBinaryString() method that directly converted the given number into Binary.

3. Program to convert decimal to binary in Java using recursion method

We can also achieve this functionality using recursion. A recursion method is a method that repeatedly calls itself until it satisfies a condition.

Program:

import java.util.Scanner;

public class DecimalToBinary {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        int decimal;
        System.out.print("Please enter a decimal number = ");
        decimal = input.nextInt();
        System.out.print("\n Decimal number = " + decimal + "\n Binary Number= ");
        getReverse(decimal, new int[20], 0);
    }

    static void getReverse(int decimal, int[] binary, int i) {
        if (decimal != 0) {
            binary[i] = decimal % 2; // storing remainder in array named binary 
// Storing quotient within decimal variable itself, so that it shrinks down to 0
            decimal = decimal / 2;
            i = i + 1;
            getReverse(decimal, binary, i);
        } else {
            while (i >= 0) {
                System.out.print(binary[i]);
                i = i - 1;
            }
        }
    }
}

Output:

Please enter a decimal number = 79 
Decimal number = 79
Binary Number= 01001111