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 }