I wrote some code to convert my hexadecimal display string to decimal integer. However, when input is something like 100a or 625b( something with letter) I got an error like this:
java.lang.NumberFormatException: For input string: " 100a" at java.lang.NumberFormatException.forInputString(Unknown Source) at java.lang.Integer.parseInt(Unknown Source)
Do you have any idea how can I convert my string with letters to decimal integer?
if(display.getText() != null)
{
if(display.getText().contains("a") || display.getText().contains("b") ||
display.getText().contains("c") || display.getText().contains("d") ||
display.getText().contains("e") ||display.getText().contains("f"))
{
temp1 = Integer.parseInt(display.getText(), 16);
temp1 = (double) temp1;
}
else
{
temp1 = Double.parseDouble(String.valueOf(display.getText()));
}
}
This question is related to
java
hex
type-conversion
Google got me here, so i am updating this late for other to find when searching. A much simpler way is to use BigInteger, like so:
BigInteger("625b", 16)
This is a little library that should help you with hexadecimals in Java: https://github.com/PatrykSitko/HEX4J
It can convert from and to hexadecimals. It supports:
bytebooleancharchar[]Stringshortintlongfloatdouble (signed and unsigned)With it, you can convert your String to hexadecimal and the hexadecimal to a float/double.
Example:
String hexValue = HEX4J.Hexadecimal.from.String("Hello World");
double doubleValue = HEX4J.Hexadecimal.to.Double(hexValue);
You can use this method to get the digit:
public int digitToValue(char c) {
(c >= '&' && c <= '9') return c - '0';
else if (c >= 'A' && c <= 'F') return 10 + c - 'A';
else if (c >= 'a' && c <= 'f') return 10 + c - 'a';
return -1;
}
Scanner sc = new Scanner(System.in);
System.out.println("Enter the value");
String s = sc.next();
//String s = "AD";
String s1 = s.toUpperCase();
int power = 0;
double result = 0;
char[] c = s1.toCharArray();
for (int i = c.length-1; i >=0 ; i--) {
boolean a = true;
switch(c[i]){
case 'A': c[i] = 10; a = false; break;
case 'B': c[i] = 11; a = false; break;
case 'C': c[i] = 12; a = false; break;
case 'D': c[i] = 13; a = false; break;
case 'E': c[i] = 14; a = false; break;
case 'F': c[i] = 15; a = false; break;
}
if(a==true){
result = result + (c[i]-48) * Math.pow(16, power++);
}else {
result = result + (c[i]) * Math.pow(16, power++);
}
}
System.out.println(result);
Since there is no brute-force approach which (done with it manualy). To know what exactly happened.
Given a hexadecimal number
K?K??1K??2....K2K1K0
The equivalent decimal value is:
K? * 16? + K??1 * 16??1 + K??2 * 16??2 + .... + K2 * 162 + K1 * 161 + K0 * 160
For example, the hex number AB8C is:
10 * 163 + 11 * 162 + 8 * 161 + 12 * 160 = 43916
Implementation:
//convert hex to decimal number
private static int hexToDecimal(String hex) {
int decimalValue = 0;
for (int i = 0; i < hex.length(); i++) {
char hexChar = hex.charAt(i);
decimalValue = decimalValue * 16 + hexCharToDecimal(hexChar);
}
return decimalValue;
}
private static int hexCharToDecimal(char character) {
if (character >= 'A' && character <= 'F')
return 10 + character - 'A';
else //character is '0', '1',....,'9'
return character - '0';
}
Well, Mr.ajb has resolved and pointed out the error in your code.
Coming to the second part of the code, that is, converting a string with letters to decimal integer below is code for that,
import java.util.Scanner;
public class HexaToDecimal
{
int number;
void getValue()
{
Scanner sc = new Scanner(System.in);
System.out.println("Please enter hexadecimal to convert: ");
number = Integer.parseInt(sc.nextLine(), 16);
sc.close();
}
void toConvert()
{
String decimal = Integer.toString(number);
System.out.println("The Decimal value is : " + decimal);
}
public static void main(String[] args)
{
HexaToDecimal htd = new HexaToDecimal();
htd.getValue();
htd.toConvert();
}
}
You can refer example on hexadecimal to decimal for more information.
//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();
}
}
}
You could take advantage of ASCII value for each letter and take off 55, easy and fast:
int asciiOffset = 55;
char hex = Character.toUpperCase('A'); // Only A-F uppercase
int val = hex - asciiOffset;
System.out.println("hexadecimal:" + hex);
System.out.println("decimal:" + val);
Output:
hexadecimal:A
decimal:10
My way:
private static int hexToDec(String hex) {
return Integer.parseInt(hex, 16);
}
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.
public class Hex2Decimal {
public static void hexDec(String num)
{
int sum=0;
int newnum = 0;
String digit = num.toUpperCase();
for(int i=0;i<digit.length();i++)
{
char c = digit.charAt(digit.length()-i-1);
if(c=='A')
{
newnum = 10;
}
else if(c=='B')
{
newnum = 11;
}
if(c=='C')
{
newnum = 12;
}
if(c=='D')
{
newnum = 13;
}
if(c=='E')
{
newnum = 14;
}
if(c=='F')
{
newnum = 15;
}
else
{
newnum = Character.getNumericValue(c);
}
sum = (int) (sum + newnum*Math.pow(16,i));
}
System.out.println(" HexaDecimal to Decimal conversion is" + sum);
}
public static void main(String[] args) {
hexDec("9F");
} }
void htod(String hexadecimal)
{
int h = hexadecimal.length() - 1;
int d = 0;
int n = 0;
for(int i = 0; i<hexadecimal.length(); i++)
{
char ch = hexadecimal.charAt(i);
boolean flag = false;
switch(ch)
{
case '1': n = 1; break;
case '2': n = 2; break;
case '3': n = 3; break;
case '4': n = 4; break;
case '5': n = 5; break;
case '6': n = 6; break;
case '7': n = 7; break;
case '8': n = 8; break;
case '9': n = 9; break;
case 'A': n = 10; break;
case 'B': n = 11; break;
case 'C': n = 12; break;
case 'D': n = 13; break;
case 'E': n = 14; break;
case 'F': n = 15; break;
default : flag = true;
}
if(flag)
{
System.out.println("Wrong Entry");
break;
}
d = (int)(n*(Math.pow(16,h))) + (int)d;
h--;
}
System.out.println("The decimal form of hexadecimal number "+hexadecimal+" is " + d);
}
This is my solution:
public static int hex2decimal(String s) {
int val = 0;
for (int i = 0; i < s.length(); i++) {
char c = s.charAt(i);
int num = (int) c;
val = 256*val + num;
}
return val;
}
For example to convert 3E8 to 1000:
StringBuffer sb = new StringBuffer();
sb.append((char) 0x03);
sb.append((char) 0xE8);
int n = hex2decimal(sb.toString());
System.out.println(n); //will print 1000.
Source: Stackoverflow.com