Java program for binary to decimal conversion

There are two following ways to convert binary number to decimal number:

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

Method 1: Binary to Decimal conversion using Integer.parseInt() method

The Integer.parseInt() method accepts two arguments, first argument is the string which you want to parse and the second argument is the radix. Here, we provided the radix as 2, because we are converting a binary number. The radix is the base of the number we are converting, for example: radix is 8 for octal number conversion, for hex to decimal radix 16 and so on.

import java.util.Scanner;
class BinaryToDecimal {
    public static void main(String args[]){
       Scanner input = new Scanner( System.in );
       System.out.print("Enter a binary number: ");
       String binaryString =input.nextLine();
       System.out.println("Output: "+Integer.parseInt(binaryString,2));
    }
}

Output:

Enter a binary number: 1101
Output: 13

Method 2: Conversion without using parseInt

Here, we are not using the parseInt() method. We have created a user defined method BinaryToDecimal(), where we have written the logic for binary to decimal conversion.

public class Details {
 
  public int BinaryToDecimal(int binaryNumber){
 
    int decimal = 0;
    int p = 0;
    while(true){
      if(binaryNumber == 0){
        break;
      } else {
          int temp = binaryNumber%10;
          decimal += temp*Math.pow(2, p);
          binaryNumber = binaryNumber/10;
          p++;
       }
    }
    return decimal;
  }
 
  public static void main(String args[]){
    Details obj = new Details();
    System.out.println("110 --> "+obj.BinaryToDecimal(110));
    System.out.println("1101 --> "+obj.BinaryToDecimal(1101));
    System.out.println("100 --> "+obj.BinaryToDecimal(100));
    System.out.println("110111 --> "+obj.BinaryToDecimal(110111));
  }
}

Output:

110 --> 6
1101 --> 13
100 --> 4
110111 --> 55

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• Java Decimal to Binary Conversion