JAVA 集合---collection定义的需方法

Posted 2021-03-09 行尸走肉

 

引用自 JAVA SE API

boolean	add(E e) Ensures that this collection contains the specified element (optional operation).
boolean	addAll(Collection<? extends E> c) Adds all of the elements in the specified collection to this collection (optional operation).
void	clear() Removes all of the elements from this collection (optional operation).
boolean	contains(Object o) Returns true if this collection contains the specified element.
boolean	containsAll(Collection<?> c) Returns true if this collection contains all of the elements in the specified collection.
boolean	isEmpty() Returns true if this collection contains no elements.
abstract Iterator<E>	iterator() Returns an iterator over the elements contained in this collection.
boolean	remove(Object o) Removes a single instance of the specified element from this collection, if it is present (optional operation).
boolean	removeAll(Collection<?> c) Removes all of this collection‘s elements that are also contained in the specified collection (optional operation).
boolean	retainAll(Collection<?> c) Retains only the elements in this collection that are contained in the specified collection (optional operation).
abstract int	size() Returns the number of elements in this collection.
Object[]	toArray() Returns an array containing all of the elements in this collection.
<T> T[]	toArray(T[] a) Returns an array containing all of the elements in this collection; the runtime type of the returned array is that of the specified array.
String	toString() Returns a string representation of this collection.