📅  最后修改于: 2020-11-14 06:09:40             🧑  作者: Mango
java.util.ArrayList类提供可调整大小的数组并实现List接口。以下是有关ArrayList的要点-
它实现所有可选的列表操作,并且还允许所有元素(包括null)。
它提供了一些方法来操纵内部用于存储列表的数组的大小。
与LinkedList实现相比,常数因子较低。
以下是java.util.ArrayList类的声明-
public class ArrayList
extends AbstractList
implements List, RandomAccess, Cloneable, Serializable
此处
ArrayList list = new ArrayList();
Sr.No. | Constructor & Description |
---|---|
1 |
ArrayList() This constructor is used to create an empty list with an initial capacity sufficient to hold 10 elements. |
2 |
ArrayList(Collection extends E> c) This constructor is used to create a list containing the elements of the specified collection. |
3 |
ArrayList(int initialCapacity) This constructor is used to create an empty list with an initial capacity. |
Sr.No. | Method & Description |
---|---|
1 | boolean add(E e)
This method appends the specified element to the end of this list. |
2 | void add(int index, E element)
This method inserts the specified element at the specified position in this list. |
3 | boolean addAll(Collection extends E> c)
This method appends all of the elements in the specified collection to the end of this list, in the order that they are returned by the specified collection’s Iterator |
4 | boolean addAll(int index, Collection extends E> c)
This method inserts all of the elements in the specified collection into this list, starting at the specified position. |
5 | void clear()
This method removes all of the elements from this list. |
6 | Object clone()
This method returns a shallow copy of this ArrayList instance. |
7 | boolean contains(Object o)
This method returns true if this list contains the specified element. |
8 | void ensureCapacity(int minCapacity)
This increases the capacity of this ArrayList. |
9 | E get(int index)
This method returns the element at the specified position in this list. |
10 | int indexOf(Object o)
This method returns the index of the first occurrence of the specified element in this list, or -1 if this list does not contain the element. |
11 | boolean isEmpty()
This method returns true if this list contains no elements. |
12 | int lastIndexOf(Object o)
This method returns the index of the last occurrence of the specified element in this list, or -1 if this list does not contain the element. |
13 | E remove(int index)
This method removes the element at the specified position in this list. |
14 | boolean remove(Object o)
This method removes the first occurrence of the specified element from this list, if it is present. |
15 | protected void removeRange(int fromIndex, int toIndex)
This method removes from this list all of the elements whose index is between fromIndex(inclusive) and toIndex(exclusive). |
16 | E set(int index, E element)
This method replaces the element at the specified position in this list with the specified element. |
17 | int size()
This method returns the number of elements in this list. |
18 | Object[] toArray()
This method returns an array containing all of the elements in this list in proper sequence (from first to last element). |
19 | This method returns an array containing all of the elements in this list in proper sequence (from first to last element); the runtime type of the returned array is that of the specified array. |
20 | void trimToSize()
This method trims the capacity of this ArrayList instance to be the list’s current size. |
此类从以下类继承方法-