This gist demonstrates the methods for binary to decimal and decimal to binary conversion

BinaryDecimalConversion.java

package org.redquark.help.march19;

import java.util.Scanner;

/**
 * 
 * @author Anirudh Sharma
 *
 */
public class BinaryDecimalConversion {

	public static void main(String[] args) {

		// Create a scanner instance to get the input from the user
		Scanner input = new Scanner(System.in);

		// Get the binary number which needs to be converted into decimal
		int binary = Integer.parseInt(input.next());

		// Converting binary to decimal
		System.out.println(binary + " ==> " + binaryToDecimal(binary));

		// Get the decimal which needs to be converted into binary
		int decimal = input.nextInt();

		// Converting decimal to binary
		decimalToBinary(decimal);

		// Closing the Scanner to avoid memory leaks
		input.close();
	}

	/**
	 * This method accepts binary argument and convert it into decimal
	 * @param binary
	 * @return decimal equivalent
	 */
	private static int binaryToDecimal(int binary) {

		// Decimal equivalent
		int decimal = 0;

		// The place determines the exponent of 2
		int place = 0;

		// Divide the number by 10 until true
		while (true) {

			if (binary == 0) {
				break;
			} else {

				int temp = binary % 10;

				// Decimal should be added to its previous value and the place raised to the power 2
				decimal += temp * Math.pow(2, place);
				
				// Move to more significant digit
				binary = binary / 10;

				// Increment place for more significant digit
				place++;
			}
		}

		return decimal;
	}

	/**
	 * This method converts decimal input to its binary equivalent
	 * @param decimal
	 */
	private static void decimalToBinary(int decimal) {

		// Array that will store the binary digits
		int[] binary = new int[40];

		// This variable will store the index of each binary digit
		int index = 0;

		// Divide the decimal by 2 until possible
		while (decimal > 0) {

			// Remainders after dividing the decimal by 2 will be stored
			binary[index++] = decimal % 2;

			// Move forward
			decimal = decimal / 2;

		}

		// Prints the binary digits in the reverse order
		for (int i = index - 1; i >= 0; i--) {

			System.out.print(binary[i]);
		}
	}
}