How to Convert Hex String to Int in Java

1. Java Convert a Short Hex String to int Using Integer.decode()
2. Java Convert a Long Hex String to int Using Long.parseLong()
3. Java Convert a Very Long Hex String to int Using BigInteger

This article will introduce the three methods that we can use to convert a hex string into an int. Hex or hexadecimal is a 16-base numbering system that means that there are 16 possible symbols representing numbers. The hex values used to represent numbers are 0-9 in decimal and A-F representing 10-15 in the decimal system.

In the following examples, we will have a look at the steps to convert a given hexadecimal string of different lengths to an int in Java.

Java Convert a Short Hex String to int Using Integer.decode()

In the first example, we are using the decode() function of the Integer class that takes a String and then returns a primitive int.

In Java, an int can store the minimum value of -2³¹ to the maximum value of 2³¹-1. If we want our result in the int type, we cannot work on long strings. Further examples in this article will show how we can convert longer hexadecimal values into a numeric value.

public class Main {
  public static void main(String[] args) {
    String hex = "0x2fd";

    int convertedValue = Integer.decode(hex);
    System.out.print(convertedValue);
  }
}

Output:

765

Java Convert a Long Hex String to int Using Long.parseLong()

As we discussed above, we cannot convert large hex values to primitive int because it can return value out of an int capacity. This is why in this example we are using Long that has a larger capacity of -2⁶³ to 2⁶³-1.

The parseLong() method of Long takes two parameters, a string and a base value, to parse the string to a primitive long integer.

public class Main {
  public static void main(String[] args) {
    String hex = "AA0F245C";
    long l = Long.parseLong(hex, 16);
    System.out.println(l);
  }
}

Output:

2853119068

Java Convert a Very Long Hex String to int Using BigInteger

Hexadecimal values can be used for various purposes, and one of them is when we want to encrypt something, this hex value can be very long. If we want to convert this hex to a numeric value for some reason, then we can use BigInteger, which can hold large integers, as its name indicates.

In the following example, we pass our hex value to the constructor of BigInteger with the base value. We can also get the int value from BigInteger.intValue(), but it will only return the starting 32 bits.

import java.math.BigInteger;

public class Main {
  public static void main(String[] args) {
    String hex = "4D21C5BA77D06212F39E16BF2756E9811125F7FC";
    BigInteger bigInteger = new BigInteger(hex, 16);
    System.out.println(bigInteger);
  }
}

Output:

440345438517096076415390637616379300179635206140