error in java.lang.ClassLoader.loadClass(Unknown Source)

Question

For my thesis I am trying to handle some things with pictures and one of the steps to complete it is to find corners in a picture. After some surfing I found that it can be implemented with Moravec's algorithm for corner detection. By luck, I found the Moravec's algorithm already implemented by JFeatureLib at this link: https://code.google.com/p/jfeaturelib/source/browse/src/main/java/de/lmu/ifi/dbs/jfeaturelib/pointDetector/Moravec.java?r=8d96a8fa9a43a0ec7e7084b40169be56bddd6f36

(Of course I imported the jar file given from JFeatureLib in the build path of Eclipse) So I used the code at the link in my project, and wrote some code to call it. Here is the code in which I create a Frame, open the picture and call the Moravec algorithm at that link:

import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;




public class Compare{
    public Compare(){
        JFrame frame = new JFrame("Find corners in picture");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        JPanel panel = (JPanel)frame.getContentPane();
        JLabel label = new JLabel();
        label.setIcon(new ImageIcon("house.jpg"));
        panel.add(label);
        frame.setLocationRelativeTo(null);
        frame.pack();
        frame.setVisible(true);
    }
    public static void main (String[] args){
        SwingUtilities.invokeLater(new Runnable(){
            public void run(){
                new Compare();
            }
        });
        Moravec picture = new Moravec();
    }
}

The point is that it returns an error on the line

Moravec picture = new Moravec();

the error it's like this:

Exception in thread "main" java.lang.UnsupportedClassVersionError: de/lmu/ifi/dbs/jfeaturelib/pointDetector/PointDetector : Unsupported major.minor version 51.0
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClassCond(Unknown Source)
at java.lang.ClassLoader.defineClass(Unknown Source)
at java.security.SecureClassLoader.defineClass(Unknown Source)
at java.net.URLClassLoader.defineClass(Unknown Source)
at java.net.URLClassLoader.access$000(Unknown Source)
at java.net.URLClassLoader$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClassCond(Unknown Source)
at java.lang.ClassLoader.defineClass(Unknown Source)
at java.security.SecureClassLoader.defineClass(Unknown Source)
at java.net.URLClassLoader.defineClass(Unknown Source)
at java.net.URLClassLoader.access$000(Unknown Source)
at java.net.URLClassLoader$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at Compare.main(Compare.java:32)

Could you please give me some advices? Thanks a lot!

Answer 1

Unsupported major.minor version 51.0
You are trying to run a jar compiled with a newer Java version in an older Java version. The message suggest de/lmu/ifi/dbs/jfeaturelib/pointDetector/PointDetector was compiled using JDK7, but you are trying to run it with an older version (I'm guessing Java 6).

Execute java -version and see if this the case. If so, find the JDK7 on your system and use that instead to run your program.