A DESCRIPTION OF THE PROBLEM :
Both classes sun.awt.util.IdentityArrayList and sun.awt.util.IdentityLinkedList are based on object identity, as the name implies. The documentation was maybe copied & pasted from another list type and for some methods talks about being based on object equality (mentioning 'equals()').

Correct Javadoc descriptions can be seen for:
sun.awt.util.IdentityLinkedList#indexOf
sun.awt.util.IdentityLinkedList#lastIndexOf
sun.awt.util.IdentityLinkedList#remove(java.lang.Object)

Incorrect Javadoc descriptions can be seen for:
sun.awt.util.IdentityLinkedList#contains
sun.awt.util.IdentityArrayList#contains
sun.awt.util.IdentityArrayList#indexOf
sun.awt.util.IdentityArrayList#lastIndexOf
sun.awt.util.IdentityArrayList#remove(java.lang.Object)

So it looks like someone did 75% of the job right in class IdentityLinkedList but then for some did not finish the task. The same person completely forgot to update the Javadoc of IdentityArrayList.