day31--ArrayList、Vector、LinkedList

ArrayList

 

如何实现？

arrayList.remove(new Student("杨玉环",22));

源码分析：

• ArrayList

private static final int DEFAULT_CAPACITY = 10;

       DEFAULT_CAPACITY:默认容量。

         注意：如果没有向集合中添加任何元素，默认容量为0。添加任意一个元素后，容量为10。

           每次扩容大小是原来的1.5倍。

transient Object[] elementData;

　　elementDate:存放元素的数组。

private int size;

　　size:实际元素的个数。

• Add()

public boolean add(E e) {
        ensureCapacityInternal(size + 1);  // Increments modCount!!
        elementData[size++] = e;
        return true;
    }
 
private void ensureCapacityInternal(int minCapacity) {
        ensureExplicitCapacity(calculateCapacity(elementData, minCapacity));
    }

private static int calculateCapacity(Object[] elementData, int minCapacity) {
        if (elementData == DEFAULTCAPACITY_EMPTY_ELEMENTDATA) {
            return Math.max(DEFAULT_CAPACITY, minCapacity);
        }
        return minCapacity;
    }
 
private void ensureExplicitCapacity(int minCapacity) {
        modCount++;
​
        // overflow-conscious code
        if (minCapacity - elementData.length > 0)
            grow(minCapacity);
    }
​

private void grow(int minCapacity) {
        // overflow-conscious code
        int oldCapacity = elementData.length;
        int newCapacity = oldCapacity + (oldCapacity >> 1);
        if (newCapacity - minCapacity < 0)
            newCapacity = minCapacity;
        if (newCapacity - MAX_ARRAY_SIZE > 0)
            newCapacity = hugeCapacity(minCapacity);
        // minCapacity is usually close to size, so this is a win:
        elementData = Arrays.copyOf(elementData, newCapacity);
    } 

Vector

LinkedList

LinkedList源码分析

int size:集合的大小

Node first:链表的头节点

Node lase:链表的尾节点

void linkLast(E e) {
        final Node<E> l = last;
        final Node<E> newNode = new Node<>(l, e, null);
        last = newNode;
        if (l == null)
            first = newNode;
        else
            l.next = newNode;
        size++;
        modCount++;
    }

private static class Node<E> {
        E item;
        Node<E> next;
        Node<E> prev;
​
        Node(Node<E> prev, E element, Node<E> next) {
            this.item = element;
            this.next = next;
            this.prev = prev;
        }
    }　

ArrayList和LinkedList的区别

• 不同结构实现方式