Java Example Program to convert binary to decimal

• Famous interview java question on conversions . 
• We can convert binary to decimal in two ways
  1.Using Integer.parseInt() method
  2.Using custom logic

1.Write a Java Program to convert binary to decimal number in java without using Integer.parseInt() method.

1. import java.util.Scanner;
2. public class DecimalFromBinary {
3.  
4.     /**
5.      *www.instanceofjava.com
6.      */
7.  
8.  public static void main(String[] args) {
9.         
10.  Scanner in = new Scanner( System.in );
11.  System.out.println("Enter a binary number: ");
12.  
13.   int  binarynum =in.nextInt();
14.   int binary=binarynum;
15.         
16. int decimal = 0;
17. int power = 0;
18.  
19. while(true){
20.  
21.  if(binary == 0){
22.  
23.         break;
24.  
25.  } else {
26.  
27.    int tmp = binary%10;
28.    decimal += tmp*Math.pow(2, power);
29.    binary = binary/10;
30.    power++;
31.  
32.  }
33. }
34.         System.out.println("Binary="+binary+" Decimal="+decimal); ;
35. }
36.  
37. }

Output:

1. Enter a binary number: 
2. 101
3. Binary=101 Decimal=5

2.Write a Java Program to convert binary to decimal number in java using Integer.parseInt() method.

1. import java.util.Scanner;
2. public class ConvertBinaryToDecimal{
3.  
4.     /**
5.      *www.instanceofjava.com
6.      */
7.  
8.  public static void main(String[] args) {
9.         
10.  Scanner in = new Scanner( System.in );
11.  
12.  System.out.println("Enter a binary number: ");
13.  String binaryString =input.nextLine();
14.  
15.  System.out.println("Result: "+Integer.parseInt(binaryString,2));
16. 
    
17.  
18. }
19.  
20. }

Output:

1. Enter a binary number:
2. 001
3. Result: 1

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