Java – meant by an “unbound” library or classpath container in Eclipse

classpatheclipsegroovyidejava

While recently imported a new project into eclipse, at one point when I tried to add the GROOVY_SUPPORT library it would up as "unbound" with error-X, like this:

GROOVY_SUPPORT library with red error-X

It also did not appear in the package explorer as I expected.

What precisely does this mean? Eclipse did not report any other errors. All I have it the red-X and the unbound message.

I was able to fix this via futzing with stuff (specifically removing and re-adding the Groovy nature) until it went away, but I'm curious about what was really going on.

Best Answer

Usually it means that the classpathentry in the .classpath can't be resolved. I usually see this when opening a project that was created/updated with a different plugin (or version) defining the classpath container that is unbound.

If you compare the .classpath file from when it was unbound to after the problem was fixed you should see the difference.

Fixing the problem the way you did (removing the unbound contain and re-adding it, as you did via the Groovy nature) is a simple way to fix the problem. One caveat, if you are part of a team working on the project and you get this problem then it would be a good idea to ensure all team members are on the same release of the IDE.

Related Solutions

Java – meant by immutable

Immutable means that once the constructor for an object has completed execution that instance can't be altered.

This is useful as it means you can pass references to the object around, without worrying that someone else is going to change its contents. Especially when dealing with concurrency, there are no locking issues with objects that never change

e.g.

class Foo
{
     private final String myvar;

     public Foo(final String initialValue)
     {
         this.myvar = initialValue;
     }

     public String getValue()
     {
         return this.myvar;
     }
}

Foo doesn't have to worry that the caller to getValue() might change the text in the string.

If you imagine a similar class to Foo, but with a StringBuilder rather than a String as a member, you can see that a caller to getValue() would be able to alter the StringBuilder attribute of a Foo instance.

Also beware of the different kinds of immutability you might find: Eric Lippert wrote a blog article about this. Basically you can have objects whose interface is immutable but behind the scenes actual mutables private state (and therefore can't be shared safely between threads).

Eclipse – What do the icons in Eclipse mean

This is a fairly comprehensive list from the Eclipse documentation. If anyone knows of another list — maybe with more details, or just the most common icons — feel free to add it.

Latest: JDT Icons

2019-06: JDT Icons

2019-03: JDT Icons

2018-12: JDT Icons

2018-09: JDT Icons

Photon: JDT Icons

Oxygen: JDT Icons

Neon: JDT Icons

Mars: JDT Icons

Luna: JDT Icons

Kepler: JDT Icons

Juno: JDT Icons