|Collection
||List
||Set
||Queue
我们来看看List的JDK,因为他继承Collection,我们关心它与Set、Collection的区别(和Collection相同的部分就略过不写注释,可参照Collection):
//We can know List is interface and extends Collection
public interface List<E> extends Collection<E> {
///// Query Operations
int size();
boolean isEmpty();
boolean contains(Object o);
Iterator<E> iterator();
Object[] toArray();
<T> T[] toArray(T[] a);
///// Modification Operations
//Return true if added, appends the element to the end of this list
boolean add(E e);
//Return true if removed, remove the first occurrence from this list
boolean remove(Object o);
///// Bulk Modification Operations
boolean containsAll(Collection<?> c);
//Return true if all added, appends all the elements of c to this list
boolean addAll(Collection<? extends E> c);
//Return true if all added, insert all the elements of c to this list at index
boolean addAll(int index, Collection<? extends E> c);
/**In my view, the two operations is hard to achieve based on LinkedList**/
boolean removeAll(Collection<?> c);
boolean retainAll(Collection<?> c);
default void replaceAll(UnaryOperator<E> operator) {}
//Sort the list according to the comparator c
default void sort(Comparator<? super E> c) {
Object[] a = this.toArray();
Arrays.sort(a, (Comparator) c);
ListIterator<E> i = this.listIterator();
for (Object e : a) {
i.next();
i.set((E) e);
}
}
void clear();
///// Comparison and hashing
boolean equals(Object o);
int hashCode();
///// Positional Access Operations
//Return the element at index position
E get(int index);
//Replace the element at index position with the new element, return the previous
E set(int index, E element);
//Insert the element at index
void add(int index, E element);
//Return the element removed, remove the element at index
E remove(int index);
///// Search Operations
//Return the index of first occurrence that is equal to 0,
// return -1 if there is no such an element
int indexOf(Object o);
//Return the index of last occurrence that is equal to 0,
// return -1 if there is no such an element
int indexOf(Object o);
///// List Iterators
ListIterator<E> listIterator();
ListIterator<E> listIterator(int index);
}
///// View
List<E> subList(int fromIndex, int toIndex);
default Spliterator<E> spliterator() {
}
List的实现基础如果是链表,一些方法实现很麻烦,像这两个操作:
boolean removeAll(Collection<?> c);
boolean retainAll(Collection<?> c);
从一个链表删除,它和另一个链表的交集,如果是无序的话,时间复杂度很高;
同理,保留交集,删除其他的, 也麻烦。
所以LinkedList源码里没有这两个方法。
由此也可以初步地引出ArrayList和LinkedList的区别:一个的底层是数组,一个的底层是链表