Scanner.next() - Exception in thread "main" java.util.InputMismatchException

Question

Hi guys I am a total newbie. Please help me.

The program is:

import java.util.Scanner.*;
import java.lang.*;
public class HexToDecimalFromWeb{
public static void main (String [] args) {
    Scanner input = new Scanner(System.in);
    printHeader();
    while (true) {
        String hex = input.next("Enter a hexadecimal number: ");
        int dec = Integer.parseInt(hex, 16);
        if (dec == SENTINEL) {
            break;
        }
        System.out.println(hex + " hex = " +  
         Integer.toString(dec)+ "decimal");
    }
}
private static void printHeader() {
    System.out.println("This program converts hexadecimal to decimal.");
   System.out. println("Enter 0 to stop.");
}
private static final int SENTINEL = 0;
}

The error I get is this:

java.lang.NoClassDefFoundError: HexToDecimalFromWeb
Caused by: java.lang.ClassNotFoundException: HexToDecimalFromWeb
at java.net.URLClassLoader$1.run(URLClassLoader.java:202)

What is the reason for that?

I think it may be an issue with Eclipse as some other programs won't run either.

11.2019 UPDATE :

I tried to execute this code again in a different IDE, this is not a problem with Eclipse. The error I am getting is this:

Exception in thread "main" java.util.InputMismatchException
at java.base/java.util.Scanner.throwFor(Scanner.java:939)
at java.base/java.util.Scanner.next(Scanner.java:1594)
at java.base/java.util.Scanner.next(Scanner.java:1525)
at HexToDecimalFromWeb.main(HexToDecimalFromWeb.java:12)

I cannot add the rest of an error as the website states that the most of my post is code. Please find it below: at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(URLClassLoader.java:190) at java.lang.ClassLoader.loadClass(ClassLoader.java:306) at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301) at java.lang.ClassLoader.loadClass(ClassLoader.java:247) Exception in thread "main" — Marcin Kulik, Sep 12 '16 at 23:08
Are you using an IDE or are you compiling straight from the command line? — , Sep 12 '16 at 23:09
First learn the difference between compiling and running a compiled program. This isn't a compile-time error. — chrylis -cautiouslyoptimistic-, Sep 12 '16 at 23:09

Imbar M. · Answer 1 · 2016-09-12T23:12:24.027

0

this line is broken:

 Integer.toString(dec)+decimal");

add " like this ->

 Integer.toString(dec)+"decimal");

edited Sep 12 '16 at 23:12

answered Sep 12 '16 at 23:09

Imbar M.

1,074
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2

I think OP wanted `" decimal"`. Removing the `"` isn't going to compile. – Elliott Frisch Sep 12 '16 at 23:11
I have "decimal" in my IDE. I do not understand why it was copied here like that with only one '' – Marcin Kulik Sep 12 '16 at 23:18
this is not solving the problem , the program won't compile – Marcin Kulik Sep 13 '16 at 01:12

score 0 · Accepted Answer · answered Nov 10 '19 at 23:24

The problem was the below line:

String hex = input.next("Enter a hexadecimal number: ");

Java Scanner method next() does not accept a random String as its argument. It can either have no argument or an argument such as String pattern or Pattern pattern.

These are the declarations of next() method:

public String next()  
public String next(String pattern)  
public String next(Pattern pattern)

Scanner.next() - Exception in thread "main" java.util.InputMismatchException

2 Answers2