I am trying to use Notepad++ as my all-in-one tool edit, run, compile, etc.

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 versions 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?