LinkedList和ArrayList简述

1. ArrayList

1.指南

ArrayList继承自实现List接口的AbstractList类,该List接口继承自Collection和Iterable（可迭代接口）接口

1. ArrayList Features

Ordered :
Index based
Dynamic resizing
Non synchronized
Duplicates allowed

2. Internal Working of ArrayList

ArrayList.java

public class ArrayList<E> extends AbstractList<E>  implements List<E>, RandomAccess,                    Cloneable, java.io.Serializable {  
    transient Object[] elementData;     //backing array 
    private int size;                   //array or list size  
    //more code
}

3. ArrayList Example

3.1 Create ArrayList

//Empty arrayList
List<String> names=new ArrayList<String>();

//ArrayList initialized with another collection
List<Integer> numbers=new ArrayList<>(Arrays.asList(1,2,3,4,5));

3.2 Add and remove Element

//Create arrayList
List<String> names=new ArrayList();

names.add("wang");   //[wang]
names.add("FEEL");   //[wang,FEEL]

names.set(1,"brain");   //[wang,brain]

names.remove(1);        //[wang]

3.3 Iterate

使用iterator()或者listIterator()获得迭代器实例的引用，这个迭代器可用来迭代arrayList中的元素.

Iterate arrayList

ArrayList<Integer> list=new ArrayList<>(Arrays.asList(1,2,3,4,5,6));

Iterator<Integer> it=list.iterator();

while(it.hasNext()){
    System.out.println(it.next());
}

程序输出：

Console

4. ArrayList Methods

add()
addAll()
clear()
clone()
contains()
forEach()
get()
indexOf()
listIterator()
remove
removeAll()
replaceAll()
sort()
subList()
toArray()

2. LinkedList

LinkedList类是List和Deque接口的双链表实现,它实现了所有的list操作.

1. Hierarchy

LinkedList类继承自AbstractSequentialList类并实现List和Deque接口,这里的E是Linkedlist存储值的类型.

LinkedList.java

public class LinkedList<E> extends AbstractSequentialList<E>
 	implements List<E>,Deque<E>,Cloneable,java.io.Serializable{
 		//implementation
 }

LinkedList和ArrayList简述

2. Features

双链表的实现，实现了List和Deque接口。因此，它还可以被用作Queue,Deque，Stack。
允许所有元素，包括复制和NULL
LinkedList维护元素的插入顺序
它不是同步的，如果多个线程同时访问一个list，并且至少有一个线程修改list的结构，，则它必须从外部同步。
使用Collections.synchronizedList(new LinkedList())得到一个同步（synchronized)的linkedlist。
迭代器通过这个类返回时是fail-fast（快速失败)的，可能会产生异常：ConcurrentModificationException.
它不实现RandomAccess接口，因此我们只能按顺序访问其中元素，不支持随机访问元素。
可以使用ListIterator迭代遍历LinkedList元素

3. Constructors

LinkedList()：初始化一个空的LinkedList实现
LinkedListExample(Collection c):初始化包含指定集合元素的LinkedList

4. Methods

boolean add(Object o)
void add(int index,Object element)
void addFirst(Object o)
void addLast(Object o)
int size()
boolean contains(Object o)
boolean remove(Object o)
Object getFirst()
int indexOf(Object o)
Object[] toArray()
Iterator iterator()
List subList(int fromIndex,int toIndex)

5. Example

5.1 Add,remove,iterate

LinkedListExample examples

import java.util.*;

public class LinkedListExample{
    public static void main(String[] args) {
        LinkedList<String> linkedList=new LinkedList<>();

        linkedList.add("A");
        linkedList.add("B");
        linkedList.add("C");
        linkedList.add("D");

        System.out.println(linkedList);

        linkedList.add(4,"A");
        linkedList.add(5,"A");

        System.out.println(linkedList);

        linkedList.remove("A");  //removes A
        linkedList.remove(0);    //remove B

        System.out.println(linkedList);

        //Iterate
        ListIterator<String> it=linkedList.listIterator();
        while(it.hasNext()){
            System.out.println(it.next());
        }
    }
}

输出结果：

[A, B, C, D]
[A, B, C, D, A, A]
[C, D, A, A]
C
D
A
A

5.2 Convert between Array and LinkedList

import java.util.*;

public class TestLinkedList{
    public static void main(String[] args) {
        LinkedList<String> linkedList=new LinkedList<>();

        linkedList.add("A");
        linkedList.add("B");
        linkedList.add("C");
        linkedList.add("D");

       // LinkedList to Array
       String[] array=new String[linkedList.size()];
       linkedList.toArray(array);
       System.out.println(Arrays.toString(array));

       //Array to LinkedList
       LinkedList<String> list=new LinkedList<>(Arrays.asList(array));
       System.out.println(list);

    }
}

输出结果:

[A, B, C, D]
[A, B, C, D]

5.3 How to sort LinkedList

Collections.sort()
Collections.sort(linkedList,comparator)

import java.util.*;

public class TestSort{
    public static void main(String[] args) {
        LinkedList<String> linkedList=new LinkedList<>();

        linkedList.add("A");
        linkedList.add("B");
        linkedList.add("C");
        linkedList.add("D");

       //unsorted
       System.out.println(linkedList);

       //Sort the list
       Collections.sort(linkedList);
       System.out.println(linkedList);

        //Custom sorting
        Collections.sort(linkedList,Collections.reverseOrder());
        System.out.println(linkedList);

    }
}