Java Convert integer to hex integer

The easiest way is to use Integer.toHexString(int)

public static int convert(int n) {
  return Integer.valueOf(String.valueOf(n), 16);
}

public static void main(String[] args) {
  System.out.println(convert(20));  // 32
  System.out.println(convert(54));  // 84
}

That is, treat the original number as if it was in hexadecimal, and then convert to decimal.

Another way to convert int to hex.

String hex = String.format("%X", int);

You can change capital X to x for lowercase.

Example:

String.format("%X", 31) results 1F.

String.format("%X", 32) results 20.

int orig = 20;
int res = Integer.parseInt(""+orig, 16);

You could try something like this (the way you would do it on paper):

public static int solve(int x){
    int y=0;
    int i=0;

    while (x>0){
        y+=(x%10)*Math.pow(16,i);
        x/=10;
        i++;
    }
    return y;
}

public static void main(String args[]){
    System.out.println(solve(20));
    System.out.println(solve(54));
}

For the examples you have given this would calculate: 0*16^0+2*16^1=32 and 4*16^0+5*16^1=84