Eclipse Java Project：工作代码中出现“找不到源”投诉

Question

Everything in an Eclipse Java project is working fine but when I override toString() and equals() a green arrow I do not recognize appears in the margin of the text editor beside the start of the overriding method declaration. When I click on it I get a new tab in the editor titled "Class File Editor" and the message under an apparent "Source not found" complaint reads:

The JAR file C:/Program Files/Java/jre7/lib/rt.jar has no source attachment.

and there is an option to add the apparently missing source. However, the code works just fine as is. For example, the output of this:

class TestClass
{
   @Override
   public String toString() // <--- green arrow appears in the margin on this line
   {
      return "Class TestClass";
   }

   public static void main(String[] args)
   {
      TestClass tc = new TestClass();
      System.out.println(tc.toString());
   }
}

Is the expected:

Class TestClass

despite the apparent complaint.

Various other posters seem to have encounted a similar complaint with actual consequences while debugging but that is not the case here. Can someone explain what is happening and what, if anything, I should do about it?

Answer 1

It's a message where the classpath for the app you're running doesn't have the sources for the rt.jar being used (more directly, Eclipse couldn't find a matching qualified source file for the class being shown). That classpath is based on the JRE System Library in the project's Java Build Path .

It's not about which one is running Eclipse. It's entirely about which one the project points to. If you want sources easily found for what's in the standard class library, set the JRE for the project to point to a JDK instead.