Java Program for Hexadecimal to Decimal Conversion

The given task is to write a Java program to convert it into its equivalent decimal number system. The base value of hexadecimal is 16, and decimal is 10.

When we convert the hexadecimal to decimal, the base value 16 will be changed to 10. The number system is of four types: Binary, Octal, Decimal, and Hexadecimal.

The base value depends on the number of digits contained by the number system. For example, the binary number system contains only two digits, 0 and 1. Hence, its base is 2.

Hexadecimal Number System

It represents the numbers from 0 to 9 and A to F. There is a total of 16 numbers available in it, and its base value is also 16. 12A₁₆, 34B₁₆, 45C₁₆ are a few examples of hexadecimal. In computers, the code for colors is generally written in hexadecimal form.

Suppose we have to store a large decimal value. If we store it in a binary numbering system, then the binary string may become very long. In this situation, we can use the hexadecimal number system that can store 4 bits of binary into 1 bit. It shortens the length of bits.

Decimal Number System

It is the most used number system. It has 10 digits from 0 to 9. Hence, its base value is 10. If the base value of a number is not mentioned, then it is considered to be 10.

A single-digit weight power 10, and every digit is 10 times more weighty than the previous one. For example, 10₁₀, 431₁₀, 980_10, etc.

Hexadecimal to Decimal Conversion

Given hexadecimal number is (54A)₁₆. To convert it to decimal, multiply each digit by 16^n-1 (where n is the number of digits) as shown below:

(54A)16 = 5 * 163-1 + 4 * 162-1 + A * 161-1
		= 5 * 162  + 4 * 161 + 10 * 160  
		= 5 * 256 + 64 + 10 
		= 1280 + 74
		= 1354 

Using Integer.parseInt() Method

The parseInt() method of the Integer class returns a decimal value according to the specified base. It is available in java.lang package. Following is the syntax of this method -

Integer.parseInt("String", base); 

Where,

• String: The value that is going to be converted.

• Base: The given value is converted according to the specified base.

Example

In this example, we will use the Integer.parseInt() method to convert hexadecimal to decimal.

public class Conversion {
   public static void main(String args[]) {  
      // Converting and storing hexadecimal value to dec1 and dec2 with base 16  
      int dec1 = Integer.parseInt("54A", 16);
      int dec2 = Integer.parseInt("41C", 16);
      System.out.println("Decimal value of given Hexadecimal: " + dec1);
      System.out.println("Decimal value of given Hexadecimal: " + dec2);
   }
}

On running, this code will show below result -

Decimal value of given Hexadecimal: 1354
Decimal value of given Hexadecimal: 1052

Using a user-defined Method

In this approach, we will define a user-defined method. Then, we will run a for loop till the length of the hexadecimal number. In that loop, we will fetch the characters, and then we will apply the logic of conversion.

Example

Following example is a practical illustration of the approach discussed above.

public class Conversion {
   public static void cnvrt(String hexNum) {
      // storing all the hexadecimal digits to this string 
      String hexStr = "0123456789ABCDEF"; 
      // converting given argument to uppercase
      hexNum = hexNum.toUpperCase();   
      int dec = 0;  
      for (int i = 0; i < hexNum.length(); i++) {  
         char ch = hexNum.charAt(i); 
         // fetching characters sequentially 
         int index = hexStr.indexOf(ch); 
         // fetching index of characters  
         dec = 16 * dec + index; 
         // applying the logic of conversion 
      }
      System.out.println("Decimal value of given Hexadecimal: " + dec); 
   }
   public static void main(String args[]) {
      // calling the function with arguments
      cnvrt("54A"); 
      cnvrt("41C");  
   }
}

Output of the above code is as follows:

Decimal value of given Hexadecimal: 1354
Decimal value of given Hexadecimal: 1052