java底层实现容器

 1 package StudyCollection;
 2 
 3 /**
 4  * 底层实现简单容器
 5  * 
 6  * @author ouyang-an 谢谢尚学堂 高琪 老师
 7  */
 8 
 9 public class MakeArray {
10     private Object[] elementData;
11     private int size;
12 
13     // 无参构造器
14     public MakeArray() {
15         this(10);  //这里默认大小是10
16     }
17 
18     // 带参构造器
19     public MakeArray(int initialCapacity) {
20         if (initialCapacity < 0) {
21             try {
22                 throw new Exception("数组越界了!");
23             } catch (Exception e) {
24                 e.printStackTrace();
25             }
26         }
27         elementData = new Object[initialCapacity];
28     }
29 
30     // add()方法
31     public void add(Object obj) {
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 
52     // 遍历
53     public void iteratesMethod() {
54         for (int i = 0; i < size; i++) {
55             Object array_element = elementData[i];
56             System.out.println(i + ":   " + array_element);
57         }
58     }
59 
60     // get方法
61     public Object get(int index) {
62         if (index >= size) {
63             try {
64                 throw new Exception();
65             } catch (Exception e) {
66                 e.printStackTrace();
67             }
68         }
69         return elementData[index];
70     }
71 
72     // set方法
73     public Object set(int index, Object nObject) {
74         return elementData[index] = nObject;
75     }
76 
77     public static void main(String[] args) {
78         MakeArray list = new MakeArray();
79         list.add("11");
80         list.add("22");
81         list.add("33");
82         list.add("44");
83         list.iteratesMethod();
84         System.out.println("------------------------");
85         System.out.println(list.size);
86         System.out.println("------------------------");
87         System.out.println(list.isEmpty());
88         System.out.println("------------------------");
89         System.out.println(list.get(3));
90         System.out.println("------------------------");
91         System.out.println(list.set(2, "ouyangan"));
92         System.out.println("------------------------");
93         list.iteratesMethod();
94     }
95 }