底层实现简单容器

 1 package StudyCollection;
 2 
 3 import java.util.Collections;
 4 
 5 /**
 6  * 底层实现简单容器
 7  * 
 8  * @author ouyang-an 谢谢尚学堂 高琪 老师
 9  */
10 
11 public class MakeArray {
12     private Object[] elementData;
13     private int size;
14 
15     public MakeArray() { // 无参构造器
16         this(10);
17     }
18 
19     public MakeArray(int initialCapacity) { // 带参构造器
20         if (initialCapacity < 0) {
21             try {
22                 throw new Exception();
23             } catch (Exception e) {
24                 e.printStackTrace();
25             }
26 
27         }
28         elementData = new Object[initialCapacity];
29     }
30 
31     public void add(Object obj) { // add()方法
32         if (size == elementData.length) {
33             Object[] newArray = new Object[size * 2];
34             System.arraycopy(elementData, 0, newArray, 0,
35                     elementData.length);
36             elementData = newArray;
37         }
38         elementData[size] = obj;
39         size++;
40     }
41 
42     // size方法
43     public int size() {
44         return size;
45     }
46 
47     // 判断数组是否为空
48     public boolean isEmpty() {
49         return size == 0;
50     }
51     //get方法
52     public Object get(int index) {
53         if (index < 0 || index >= size) {
54             try {
55                 throw new Exception();
56             } catch (Exception e) {
57                 e.printStackTrace();
58             }
59         }
60         return elementData[index];
61     }
62     //set方法
63     public Object set(int index) {
64         return elementData[index];
65     }
66     public static void main(String[] args) {
67         MakeArray list = new MakeArray();
68         list.add("a");
69         list.add("123");
70         list.add("sadf");
71         list.add("dsafas");
72         System.out.println(list.size);
73         System.out.println(list.isEmpty());
74         System.out.println(list.get(3));
75     }
76 }