The Collection interface is the parent of the List and Set interfaces, but not Map.
Present in java.util.Collection
Assume the following declaration for identifiers in the table below:
Present in java.util.Collection
Assume the following declaration for identifiers in the table below:
Collection coll;
boolean b;
Object obj;
int i;
Iterator it;
Returns | Method | Action |
---|---|---|
Adding objects to a collection | ||
b = | coll.add(obj) | Adds obj to this collection. Returns true if the collection was changed because of the add (eg, it will always be true for adding to a List, but will be false when adding to a Set that already contains this object). It appends new element at the end of the list. |
b = | coll.addAll(coll) | Adds all elements of obj to this collection. Returns true if the collection was changed because of the addition. It appends new element at the end of the list. |
Removing objects from a collection | ||
coll.clear() | Removes all elements from the collection. | |
b = | coll.remove(obj) | Removes the specified item from the list for the first occurrence of obj from this collection. Returns true if the collection was changed because of this operation. |
b = | coll.removeAll(coll) | Removes all elements of coll from this collection. Returns true if the collection was changed because of this operation. |
b = | coll.retainAll(coll) | Removes all elements of which are not in coll from this collection. Returns true if the collection was changed because of this operation. |
Testing for presence in a collection | ||
b = | coll.contains(obj) | Returns true if obj is in this collection. |
b = | coll.containsAll(coll) | Returns true if all the members of coll are in this collection. |
b = | coll.isEmpty() | Returns true if there are no objects in this collection. |
Other | ||
it = | coll.iterator() | Returns an iterator for this collection. The order of elements is only specified if the underlying collection has an ordering (eg, List and TreeSet so, HashSet doesn't). |
i = | coll.size() | Returns the number of objects in this collection. |
Object[] = | coll.toArray() | Returns an array containing the elements of this collection. |
Object[] = | coll.toArray(Object[]) | Returns an array containing the elements of this collection. |
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