Converting Hexadecimal String to Decimal Integer

It looks like there's an extra space character in your string. You can use trim() to remove leading and trailing whitespaces:

temp1 = Integer.parseInt(display.getText().trim(), 16 );

Or if you think the presence of a space means there's something else wrong, you'll have to look into it yourself, since we don't have the rest of your code.

  public static int hex2decimal(String s) {
             String digits = "0123456789ABCDEF";
             s = s.toUpperCase();
             int val = 0;
             for (int i = 0; i < s.length(); i++) {
                 char c = s.charAt(i);
                 int d = digits.indexOf(c);
                 val = 16*val + d;
             }
             return val;
         }

That's the most efficient and elegant solution I have found over the internet. Some of the others solutions provided here didn't always work for me.

//package com.javatutorialhq.tutorial;

import java.util.Scanner;

/* * Java code convert hexadecimal to decimal */ 
public class HexToDecimal {

    public static void main(String[] args) {

        // TODO Auto-generated method stub 

        System.out.print("Hexadecimal Input:");

        // read the hexadecimal input from the console 

        Scanner s = new Scanner(System.in); 

        String inputHex = s.nextLine();

        try{ 

// actual conversion of hex to decimal

            Integer outputDecimal = Integer.parseInt(inputHex, 16);

            System.out.println("Decimal Equivalent : "+outputDecimal);


        }

        catch(NumberFormatException ne){

            // Printing a warning message if the input is not a valid hex number

            System.out.println("Invalid Input"); 

        }

        finally{ s.close();

        }
    } 
}