ArrayList的用法（转载）

写一个简单的模仿ArrayList类的简单类：

实现add(),remove(),get(),set()方法。

 1 package Collection;
 2 
 3 public class MyArrayList {
 4     private Object[] objs;
 5     private int size;
 6     private int lenth;
 7     
 8     public Object[] getObjs() {
 9         return objs;
10     }
11     public int getSize() {
12         return size;
13     }
14     public int getLenth() {
15         return lenth;
16     }
17     public void setLenth(int lenth) {
18         if(lenth < 0){
19             try {
20                 throw new Exception();
21             } catch (Exception e) {
22                 // TODO Auto-generated catch block
23                 e.printStackTrace();
24             }
25         }
26         this.lenth = lenth;
27     }
28     public MyArrayList(){
29         this.lenth = 10;
30         this.objs = new Object[lenth];
31     }
32     public MyArrayList(int lenth) {
33         if(lenth < 0){
34             try {
35                 throw new Exception();
36             } catch (Exception e) {
37                 // TODO Auto-generated catch block
38                 e.printStackTrace();
39             }
40         }
41         this.objs = new Object[lenth];
42     }
43     public boolean add(Object obj){
44         Object[] oldObjectList = this.objs;
45         if(this.size == this.objs.length){
46             this.objs = new Object[2 * this.objs.length + 1];
47         }
48         System.arraycopy(oldObjectList, 0, this.objs, 0, this.size);
49         this.objs[this.size++] = obj;
50         return true;
51     }
52     public Object remove(int index){
53         Object obj = get(index);
54         Object[] oldObjectList = this.objs;
55         this.objs = new Object[this.size];
56         for(int i = 0; i < this.size; i++){
57             if(i < index){
58                 this.objs[i] = oldObjectList[i];
59             }else if(i >= index){
60                 this.objs[i] = oldObjectList[i + 1];
61             }
62         }    
63         this.size--;
64         return obj;
65     }
66     public Object get(int index){
67         checkBound(index);
68         return this.objs[index];
69     }
70     public Object set(int index, Object obj){
71         Object old = this.objs[index];
72         this.objs[index]  = obj;
73         return old;
74     }
75     private void checkBound(int index){
76         if(index < 0 || index > size){
77             try {
78                 throw new Exception();
79             } catch (Exception e) {
80                 // TODO Auto-generated catch block
81                 e.printStackTrace();
82             }
83         }
84     }
85 }

检测类：

 1 package Collection;
 2 
 3 public class test {
 4     public static void main(String args[]){
 5         MyArrayList mal = new MyArrayList();
 6         for(int i = 0; i < 9; i++){
 7             mal.add(i);
 8         }
 9         System.out.println(mal.getSize());
10         for(int i = 0; i < 9; i++){
11             System.out.print(mal.get(i) + " ");
12         }
13         System.out.println();
14         mal.remove(1);
15         System.out.println(mal.getSize());
16         for(int i = 0; i < 8; i++){
17             System.out.print(mal.get(i) + " ");
18         }
19         mal.set(1, 10);
20         System.out.println();
21         for(int i = 0; i < 8; i++){
22             System.out.print(mal.get(i) + " ");
23         }
24     }
25 }

结果：

比较简单，没写注释，凑活着看吧。