title: Using JRE vs JDK (installed JREs?!) in Eclipse, what´s better?
body: <p>I have just noticed that my Eclipse (version Luna) was running on the JRE instead of the JDK.
  I was wondering about that, because my environment variables are set correctly as !User-Variables! (JAVA_HOME and added into the PATH-value).</p>
  
  <p>I'm not an absolute beginner, so I surely know that JDK is for developers (as the name suggests) and also includes JRE. I`m just totally amazed that Eclipse, which is built to develope, only access to the Runtime Environment.</p>
  
  <p>Maybe I´m wrong and at the configuration "installed JREs" it only gets access to things like the JVM etc. and gets access to JDK at another point?!</p>
  
  <p>I stumbled upon this while I´m trying to fix a problem with parameter names from standard class methods (got arg0, arg1 etc.) and saw that the javadoc was not attached.</p>
  
  <p>Now I want to know if I should select JRE or JDK at Windows => Preferences => Java => Installed JREs? I dare guess that running a programm with JDK configured would slow it because the folder of JDK includes more data and therefore has a bigger size.
  What´s the "normal" configuration?!</p>
  
  <p>I just want to configure Eclipse correctly and close my knowledge gap, I obviously have at this context.</p>