Java容器-ArrayList

 1 int size();返回大小
 2 boolean isEmpty()非空判断
 3 boolean contains(Object o)判断o在集合内是否存在
 4 Iterator<E> iterator()集合迭代器
 5 Object[] toArray()返回包含此容器中所有元素的数组
 6 boolean remove(Object o)把o元素从集合内删除
 7 boolean add(Object obj)向容器中添加指定的元素
 8 Object get（int index）获取下标为index的那个元素
 9 Object remove（int index）删除下标为index的那个元素
10 Object set（int index,Object element）将下标为index的那个元素置为element
11 Object add（int index,Object element）在下标index的位置添加一个对象element
12 Object put(Object key,Object value)向容器中添加指定的元素
13 Object get（Object key）获取关键字为key的那个对象

  1 //指定大小的构造函数
  2 public ArrayList(int initialCapacity) {
  3     if (initialCapacity > 0) {
  4         this.elementData = new Object[initialCapacity];
  5     } else if (initialCapacity == 0) {
  6         this.elementData = EMPTY_ELEMENTDATA;
  7     } else {
  8         throw new IllegalArgumentException("Illegal Capacity: "+
  9                 initialCapacity);
 10     }
 11 }
 12 //无参数构造函数
 13 public ArrayList() {
 14     this.elementData = DEFAULTCAPACITY_EMPTY_ELEMENTDATA;
 15 }
 16 //指定内容构造函数
 17 public ArrayList(Collection<? extends E> c) {
 18     elementData = c.toArray();
 19     if ((size = elementData.length) != 0) {
 20         if (elementData.getClass() != Object[].class)
 21             elementData = Arrays.copyOf(elementData, size, Object[].class);
 22     } else {
 23         this.elementData = EMPTY_ELEMENTDATA;
 24     }
 25 }
 26//返回集合长度
 27 public int size() {
 28     return size;
 29 }
 30 //判断集合内是否有值
 31 public boolean isEmpty() {
 32     return size == 0;
 33 }
 34 //判断集合中是否存在对象o
 35 public boolean contains(Object o) {
 36     return indexOf(o) >= 0;
 37 }
 38 //返回包含此集合中所有元素的数组
 39 public Object[] toArray() {
 40     return Arrays.copyOf(elementData, size);
 41 }
 42 //获取指定位置的元素
 43 public E get(int index) {
 46     return elementData(index);
 47 }
 48 //在指定位置替换元素
 49 public E set(int index, E element) {
 52     E oldValue = elementData(index);
 53     elementData[index] = element;
 54     return oldValue;
 55 }
 56 //添加元素
 57 public boolean add(E e) {
 58  
 59     elementData[size++] = e;
 60     return true;
 61 }
 62 //在指定位置添加元素
 63 public void add(int index, E element) { 
 69     elementData[index] = element;
 70     size++;
 71 }
 72 //删除指定位置的元素
 73 public E remove(int index) {
 74  
 77     E oldValue = elementData(index);
 78 
 79     int numMoved = size - index - 1;
 80     if (numMoved > 0)
 81         System.arraycopy(elementData, index+1, elementData, index,
 82                 numMoved);
 83     elementData[--size] = null; 
 84 
 85     return oldValue;
 86 }
 87 //在指定元素
 88 public boolean remove(Object o) {
 89     if (o == null) {
 90         for (int index = 0; index < size; index++)
 91             if (elementData[index] == null) {
 92                 fastRemove(index);
 93                 return true;
 94             }
 95     } else {
 96         for (int index = 0; index < size; index++)
 97             if (o.equals(elementData[index])) {
 98                 fastRemove(index);
 99                 return true;
100             }
101     }
102     return false;
103 }
104 
105 private void fastRemove(int index) {
106     modCount++;
107     int numMoved = size - index - 1;
108     if (numMoved > 0)
109         System.arraycopy(elementData, index+1, elementData, index,
110                 numMoved);
111     elementData[--size] = null; 
112 }

 1 public class ArrayListUse {
 2     public static void main(String[] args) {
 3         List test = new ArrayList();
 4 
 5         test.add("1");
 6         test.add("2");
 7         test.add("3");
 8         test.add("4");
 9         test.add("5");
10 
11         test.add(0,5);
12         System.out.println("指定位置add:"+test.get(0));
13         System.out.println("指定位置add:"+test.get(1));
14 
15         test.remove(2);
16         System.out.println("指定位置删除"+test.get(2));
17         System.out.println("长度"+test.size());
18 
19 
20     }
21 }