title: How do I view JRE's source code in Eclipse?
body: <p>Using Eclipse I want to view the source code for a core Java class (E.g. <code>java.util.concurrent.ConcurrentHashMap</code>) but when I navigate to the source using 'Open Declaration' it says 'Source not found' and gives me the option to attach the source.</p>
  
  <p>My question is; how do i attach the source? Where do i get the source .jar from for the <code>java.util.concurrent</code> library?</p>