I have two packages, Shapes and Fruits:
com.myproject.Shapes.
    Circle
    Square
    Triangle
com.myproject.Fruits.
    Apple
           
        For another package use this syntax:
{@link  package.class#member  label}
In your case this should be:
{@link com.myproject.Shapes.Square Square}
If you want to show only the class name then use the label, if complete path is desired then label is not required.
Reference: http://docs.oracle.com/javase/7/docs/technotes/tools/windows/javadoc.html#link
The correct syntax variants are
{@link [<package>.]<class>[#<method>]}
{@link #<method>}
You were missing a complete package. The following example should be correct
{@link com.myproject.Shapes.Square} 
                     ^^^^^^