title: what is java installation structure in linux?
body: <p>When i run command <strong>which java</strong> getting output <strong>/usr/bin/java</strong></p>
  
  <p>when i run <strong>ll /usr/bin/java</strong> getting output <strong>/usr/lib/jvm/jre-1.7.0-openjdk.x86_64/bin/java</strong></p>
  
  <p>In /usr/lib/ i found following folders with 4kb size what are these folders ?</p>
  
  <pre><code>java-1.5.0-gcj-1.5.0.0
  java-1.7.0-openjdk-1.7.0.51.x86_64
  jre -&gt; /etc/alternatives/jre
  jre-1.5.0 -&gt; /etc/alternatives/jre_1.5.0
  jre-1.5.0-gcj -&gt; java-1.5.0-gcj-1.5.0.0/jre
  jre-1.7.0 -&gt; /etc/alternatives/jre_1.7.0
  jre-1.7.0-openjdk.x86_64 -&gt; java-1.7.0-openjdk-1.7.0.51.x86_64/jre
  jre-gcj -&gt; /etc/alternatives/jre_gcj
  jre-openjdk -&gt; /etc/alternatives/jre_openjdk
  </code></pre>
  
  <p>In /usr/lib/jvm/jre-1.7.0-openjdk.x86_64/bin i found java is that java file ?
  When i want to set java_home which path should i use ?
  What is excatly difference netweem jdk and these jvm folders?</p>