在 eclipse 中构建我的 java 应用程序后出错

Question

I'm learning java and tried to build a very simple app that i created in Eclipse .

The app basically just asks the user if he could see clouds at the sky. If he says yes, then the app says "oh its cloudy", if he says no, the app says "its sunshine" (all that only in german).

This is the full code of the app

import javax.swing.JOptionPane;

public class Wetteransage {

    public static void main(String[] args) {
        
        int wetterInfo = JOptionPane.showConfirmDialog(null, "Siehst du Wolken am Himmel?");
        
        switch (wetterInfo)
        {
        case 0:
            JOptionPane.showMessageDialog(null, "Dann ist es wohl bewölkt...");
            break;
        case 1:
            JOptionPane.showMessageDialog(null, "Oh wie schön, die Sonne scheint!");
            break;
        case 2:
            JOptionPane.showMessageDialog(null, "Du bist dir wohl nicht sicher, was?");
            break;
        }

    }

}

When i run it inside eclipse, everything works fine.

But when i export it and try to run the .jar file, it gives me a Error:

Error: A JNI error has occurred, please check your installation and try again.

A Java Exception as occurred.

Answer 1

One potential issue that could cause this error in Eclipse is the existing of an old version of the app in your "Run Configurations" list. To get around this problem, you could EXPLICITLY right-click the file you want to run and then select "Run As Java Application."

A better way to do this is to open your "Run Configurations" and delete old versions of it. To open your "run configurations", simply click on the black down-arrow next to your "Run" green icon and select "Run Configurations"

Once you open the Run Configurations window, go to the listed Java applications and delete the ones you don't need.

Lastly, select the Java application you want to run, and just run it. The problem, if related to this specific condition, should be gone.

UPDATE : I didn't quite see the OP last statement about the error being when executing the JAR. A JNI error while executing the JAR could be caused by one or more of the issues listed below:

1. Dependencies on 3rd-party JNI libraries (don't appear to be the case here)
2. Corrupted Java installation (I have never seen this before, but could happen)
3. "Incompatible" JREs - I have experienced all kinds of issues with having multiple versions of Java Runtime Environments in Windows machine. To avoid these issues, make sure you are using the right JRE. While I am not 100% this will result in a JNI error, I don't rule this out. One way to find out is to invoke the java command from the same Java home folder you use to compile the code.