How to fix java lang UnsupportedClassVersionError Unsupported major minor version

Question

I have JRE installed, and I have setup my path variable to the .../bin directory.

When I run my "Hello world" in Notepad++, I get this message:

java.lang.UnsupportedClassVersionError: test_hello_world :
 Unsupported major.minor version 51.0
    at java.lang.ClassLoader.defineClass1(Native Method)
    at java.lang.ClassLoader.defineClassCond(Unknown Source)
       .........................................

I think the problem here is about versions; some version of Java may be old or too new.

1. How do I fix it?
2. Should I install the JDK, and setup my path variable to the JDK instead of JRE?
3. What is the difference between the PATH variable in JRE or JDK?

Answer 1

This error means you're trying to load a Java "class" file that was compiled with a newer version of Java than you have installed.

For example, your .class file could have been compiled for JDK 7, and you're trying to run it with JDK 6.

So the solution is to either:

• Upgrade your Java runtime or

• Recompile the class if you have the source, using your local Java compiler (if you have one).

  javac FileName.java

For developers, this can happen if another developer checks in a .class file, and they've got a newer version of java than you have!