org.semanticweb.elk.util.concurrent.collections

Interface ActivationStack<E>

Type Parameters:

E - the type of elements with which this stack works

All Known Implementing Classes:

ConcurrentLinkedActivationStack, SynchronizedArrayListActivationStack

public interface ActivationStack<E>

A thread-safe stack that can additionally signal when it becomes empty and non-empty. Elements of the stack should not be null.

Author:

"Yevgeny Kazakov"

Method Summary

Modifier and Type	Method and Description
E	peek() Returns but does not remove the head element of the stack.
E	pop() Takes and removes the head element of the stack.
boolean	push(E element) Inserts the given element at the head of the stack.

Method Detail

push

boolean push(E element)

Inserts the given element at the head of the stack. Returns true if this is the first element inserted after the stack has been cleared. A stack is clear in the beginning and is cleared every time pop() returns null. Note that the stack might be empty in the sense that pop() would return null, but not cleared.

Parameters:

element - the element to be inserted at the head of the stack

Returns:

true if this is the first element inserted after the stack has been cleared.

Throws:

IllegalArgumentException - if null element is inserted

pop

E pop()

Takes and removes the head element of the stack.

Returns:

the head element in the stack or null if there are no elements in the stack

peek

E peek()

Returns but does not remove the head element of the stack. This method does not modify the stack and calling this method does not have any effect on the results of the other methods.

Returns:

the head element in the stack or null if there are no elements in the stack