The main implementation classes of list collection are:
1. ArrayList collection
Implementation of variable-size array of List interface . (Queries are fast, additions and deletions are slow.) This implementation is not synchronous (multi-threading issue).
2. LinkedList collection
The linked list implementation of the List interface. This implementation is not synchronous.
java.util.LinkedList collection implements List interface.
Features:
(1) The bottom layer is a linked list structure: slow to query, fast to add and delete.
(2) contains a large number of methods for operating the first and last elements.
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Note: Use the unique method of LinkedList collection, and you cannot use polymorphism.
—public void addFirst(E e): Insert the specified element into the beginning of this list.
—public void addLast(E e): Add the specified element to the end of this list.
—public E getFirst(): Returns the first element of this list.
—public E getLast(): Returns the last element of this list.
—public E removeFirst(): Remove and return the first element of this list.
—public E removeLast(): Removes and returns the last element of this list.
—public E pop(): Pop an element from the stack represented by this list. Equivalent to removeFirst().
—public void push(E e): Push the element into the stack represented by this list. Equivalent to addFirst(E e).
—public boolean isEmpty(): Returns true if the list does not contain elements.
—clear(); //Clear the elements in the collection, and then get the elements in the collection will throw NoSuchElementException.
3. Vector collection
can realize a growable object array. This implementation is synchronous. The earliest collection of JDK1.0 has an array at the bottom, but it is single-threaded and relatively slow.
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