手写实现List接口的ArrayList类

 1 package cn.ftf.myarraylist;
 2 
 3 public interface MyList {
 4     public void clear();
 5     public boolean isEmpty();
 6     public int length();
 7     public Object get(int i) throws Exception;
 8     public void add(Object obj);
 9     public void inset(int i,Object obj) throws Exception;
10     public void remove(int i) throws Exception;
11     public int indexOf(Object obj);
12     public void display();
13 }

 1 package cn.ftf.myarraylist;
 2 
 3 public class MyArrayList implements MyList{
 4     private Object[] obj;
 5     private int a=3;
 6     private int curLen=0;
 7     
 8 
 9     public MyArrayList() {
10         super();
11         obj=new Object[a];
12     }
13 
14     @Override
15     public void clear() {
16         curLen=0;
17     }
18 
19     @Override
20     public boolean isEmpty() {
21         return curLen==0;
22     }
23 
24     @Override
25     public int length() {
26         return curLen;
27     }
28 
29     @Override
30     public Object get(int i) throws Exception{
31         if(i<0||i>curLen-1) {
32             throw new Exception("第"+i+"个元素不存在！");
33         }
34         return obj[i];
35     }
36 
37     @Override
38     public void add(Object obj) {
39         if(curLen==a) {
40             a=a*2;
41             Object [] b=this.obj;
42             this.obj=new Object[a];
43             for(int i=0;i<=curLen-1;i++) {
44                 this.obj[i]=b[i];
45             }
46         }
47         this.obj[curLen]=obj;
48         curLen++;
49     }
50     @Override
51     public void inset(int i, Object obj) throws Exception{
52         if(i<0||i>curLen) {
53             throw new Exception("插入位置非法！");
54         }
55         if(curLen==a) {
56             a=a*2;
57             Object [] b=this.obj;
58             this.obj=new Object[a];
59             for(int i1=0;i1<=curLen-1;i1++) {
60                 this.obj[i1]=b[i1];
61             }
62         }
63         for(int ii=curLen-1;ii>=i;ii--) {
64             this.obj[ii+1]=this.obj[ii];
65         }
66         this.obj[i]=obj;
67         curLen++;
68     }
69 
70     @Override
71     public void remove(int i) throws Exception {
72         if(i<0||i>curLen) {
73             throw new Exception("移除位置非法！");
74         }
75         for(int ii=i+1;ii<=curLen;ii++) {
76             obj[ii]=obj[ii-1];
77         }
78         curLen--;
79     }
80 
81     @Override
82     public int indexOf(Object obj) {
83         for(int i=0;i<=curLen;i++) {
84             if(this.obj[i].equals(obj)) {
85                 return i;
86             }
87         }
88         return -1;
89     }
90 
91     @Override
92     public void display() {
93         for(int i=1;i<=curLen;i++) {
94             System.out.println(obj[i-1]+"  ");
95         }
96         
97     }
98 
99 }

 1 package cn.ftf.myarraylist;
 2 
 3 public class Test01 {
 4     public static void main(String[] args) throws Exception {
 5         MyArrayList ma=new MyArrayList();
 6         MyList ml=new MyArrayList();
 7         ml.add(1);
 8         ml.add("hello");
 9         ml.add(2);
10         ml.add("word");
11         ml.display();
12         
13         System.out.println(ml.get(3));
14         ml.inset(3, "插入的");
15         ml.inset(3, "插入的2");
16         ml.display();
17         System.out.println(ml.length());
18         System.out.println(ml.isEmpty());
19         ml.clear();
20         System.out.println(ml.isEmpty());
21 
22 
23     }
24 
25 }
/*
运行结果：（无差错）
1  
hello  
2  
word  
word
1  
hello  
2  
插入的2  
插入的  
word  
6
false
true
*/