The difference (advantages & disavanteges ) between Arraylist and Linkedlist
Posted 吸毒术士柯震东
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先放总结: ArrayList 在时间复杂度上表现出 查询快 更改操作消耗大的特点,而LinkedList则表现出 查询相对耗费大,而更改快的特点 所以两种list可以择优使用!
首先 放上自己打的一段 模仿 残缺的 LinkedList 代码:
1 public class linkListDemo { 2 /** 3 * first refer to the first ele 4 * last refer to the last ele , Object 5 * */ 6 private Node first = null; 7 private Node last = null; 8 9 10 /** 11 * the size of the list 12 * */ 13 private int size = 0; 14 15 16 17 /** 18 * add a new node to the last position 19 * */ 20 public void addLast(Object ele){ 21 22 //create a new node which pose on the next position of the previous one 23 Node node = new Node(ele); 24 25 //size would not be lower than zero ,so we don‘t need out-of-bound check 26 if(size == 0){ 27 /** 28 * no doubt that the first and last ele of the very first element is itself 29 * */ 30 31 /** 32 * set the first and last node of the linkedlist 33 * */ 34 this.last = node; //belongs to a linkedlist 35 this.first = node; //belongs to a linkedlist 36 } 37 else{ 38 this.last.next = node; 39 node.prev = this.last; 40 this.last = node; 41 42 43 } 44 size++; 45 } 46 47 /** 48 * remove operation a node in the linkedlist 49 * */ 50 public void remove(Node nd){ 51 52 } 53 /** 54 * add a new node to the first position 55 * */ 56 public void addFirst(){ 57 58 } 59 60 /** 61 * class node , which contain its previous node and next node , as well as its own element 62 * */ 63 class Node { 64 /** 65 * ele , pre ,next 66 * */ 67 Node(Object ele){ 68 this.ele = ele; 69 } 70 //element 71 private Object ele; 72 73 //previous 74 Node prev; 75 76 //next 77 Node next; 78 79 80 81 /** 82 * overwrite toString method 83 * */ 84 } 85 public String toString(){ 86 87 //the first node 88 Node currentNode = this.first; 89 if(size == 0){ 90 String str = "[]"; 91 return null; 92 } 93 else{ 94 StringBuffer sb = new StringBuffer(); 95 sb.append("["); 96 for(int i = 0 ; i < size; i++){ 97 98 //add element 99 sb.append(currentNode.ele); 100 currentNode = currentNode.next; 101 102 //add "," 103 if(i != (size - 1)){ 104 sb.append(","); 105 } 106 } 107 sb.append("]"); 108 109 //@return 110 return sb.toString(); 111 } 112 113 } 114 }
还有 ArrayLIst 的:
1 /** 2 * @command 学习仿作一个Arrayist 3 * */ 4 public class MyArrayList { 5 /**主体数组*/ 6 Object[] elementData; 7 /**初始化后的数组元素个数*/ 8 private int size = 0; 9 /**默认长度*/ 10 private static final Integer DEFAULT_CAPACITY = 10; 11 /**empty list that has initialized*/ 12 private static final Object[] EMPTY_ELEMENTDATA = null; 13 /** Constructor 14 * @throws Exception */ 15 public MyArrayList() throws Exception{ 16 this(DEFAULT_CAPACITY); 17 } 18 /** 19 * Constructs an empty list with the specific initial capacity 20 * @param initialCapacity the initial capacity of the list 21 * @exception IllegalArgumentException if the specific capacity 22 * is negative 23 * 24 * */ 25 public MyArrayList(Integer initialCapacity)throws IllegalArgumentException { 26 if(initialCapacity > 0){ 27 this.elementData = new Object[initialCapacity]; 28 }else if (initialCapacity ==0){ 29 this.elementData = EMPTY_ELEMENTDATA; 30 }else { 31 //真的是 实践学习得最多 :throw exception 时要用new 因为你这个是一个新的异常 如果不用new 默认当是方法 32 throw new IllegalArgumentException("Illegal capacity : " + initialCapacity); 33 } 34 } 35 public static void add(Object obj){ 36 37 } 38 39 /** 40 * return true if the arraylist is empty 41 * else return false 42 * */ 43 public boolean isEmpty(){ 44 return size == 0; 45 } 46 47 /** 48 * return the element of the specific index 49 * */ 50 public Object get(Integer index){ 51 rangeCheck(index);//checked 52 return elementData[index]; 53 } 54 55 /** 56 * to check whether if the index is out-of-bound 57 * */ 58 private void rangeCheck(Integer index) { 59 // TODO Auto-generated method stub 60 if(index > size){ 61 throw new IndexOutOfBoundsException("index");// actually Java api used outofboundmsg(which is a defined string 62 } 63 } 64 }
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