SCJP 5.0: Collections: the Collection Interface

Some methods in the Collection Interface:

boolean add(Object obj)
boolean addAll(Collection c)

void clear()

boolean contains(Object obj)
boolean containsAll(Collection c)

boolean isEmpty()

boolean equals(Object obj)

int hashcode()

boolean remove(Object obj)
boolean removeAll(Collection c)

Iterator iterator()

T[] toArray(T[] array)

For more detail see Sun's tutorial.