Java数据结构之ArrayList从顺序表到实现

public static void main(String[] args) {
	// ArrayList创建，推荐写法
	// 构造一个空的列表
	List<Integer> list1 = new ArrayList<>();
	// 构造一个具有10个容量的列表
	List<Integer> list2 = new ArrayList<>(10);
	list2.add(1);
	list2.add(2);
	list2.add(3);
	// list2.add("hello"); // 编译失败，List<Integer>已经限定了，list2中只能存储整形元素
	// list3构造好之后，与list中的元素一致
	ArrayList<Integer> list3 = new ArrayList<>(list2);
	// 避免省略类型，否则：任意类型的元素都可以存放，使用时将是一场灾难
	List list4 = new ArrayList();
	list4.add("111");
	list4.add(100);
}

public static void main(String[] args) {
	List<String> list = new ArrayList<>();
	list.add("JavaSE");
	list.add("JavaWeb");
	list.add("JavaEE");
	list.add("JVM");
	list.add("测试课程");
	System.out.println(list);
	// 获取list中有效元素个数
	System.out.println(list.size());
	// 获取和设置index位置上的元素，注意index必须介于[0, size)间
	System.out.println(list.get(1));
	list.set(1, "JavaWEB");
	System.out.println(list.get(1));
	// 在list的index位置插入指定元素，index及后续的元素统一往后搬移一个位置
	list.add(1, "Java数据结构");
	System.out.println(list);
	// 删除指定元素，找到了就删除，该元素之后的元素统一往前搬移一个位置
	list.remove("JVM");
	System.out.println(list);
	// 删除list中index位置上的元素，注意index不要超过list中有效元素个数,否则会抛出下标越界异常
	list.remove(list.size()-1);
	System.out.println(list);

public static void main(String[] args) {
	List<Integer> list = new ArrayList<>();
	list.add(1);
	list.add(2);
	list.add(3);
	list.add(4);
	list.add(5);
	// 使用下标+for遍历
	for (int i = 0; i < list.size(); i++) {
		System.out.print(list.get(i) + " ");
	} 
	System.out.println();
	// 借助foreach遍历
	for (Integer integer : list) {
		System.out.print(integer + " ");
	} 
	System.out.println();
	Iterator<Integer> it = list.listIterator();
	while(it.hasNext()){
	System.out.print(it.next() + " ");
	} 
	System.out.println();
}

Object[] elementData; // 存放元素的空间
private static final Object[] DEFAULTCAPACITY_EMPTY_ELEMENTDATA = {}; // 默认空间
private static final int DEFAULT_CAPACITY = 10; // 默认容量大小
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 static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;
	private void grow(int minCapacity) {
	// 获取旧空间大小
	int oldCapacity = elementData.length;
	// 预计按照1.5倍方式扩容
	int newCapacity = oldCapacity + (oldCapacity >> 1);
	// 如果用户需要扩容大小 超过 原空间1.5倍，按照用户所需大小扩容
	if (newCapacity - minCapacity < 0)
	newCapacity = minCapacity;
	// 如果需要扩容大小超过MAX_ARRAY_SIZE，重新计算容量大小
	if (newCapacity - MAX_ARRAY_SIZE > 0)
	newCapacity = hugeCapacity(minCapacity);
	// 调用copyOf扩容
	elementData = Arrays.copyOf(elementData, newCapacity);
}
private static int hugeCapacity(int minCapacity) {
	// 如果minCapacity小于0，抛出OutOfMemoryError异常
	if (minCapacity < 0)
	throw new OutOfMemoryError();
	return (minCapacity > MAX_ARRAY_SIZE) ? Integer.MAX_VALUE : MAX_ARRAY_SIZE;
}

public class Card {
	public int rank; // 牌面值
	public String suit; // 花色
	@Override
	public String toString() {
		return String.format("[%s %d]", suit, rank);
	}
}

import java.util.List;
import java.util.ArrayList;
import java.util.Random;
public class CardDemo {
	public static final String[] SUITS = {"♠", "♥", "♣", "♦"};
	// 买一副牌
	private static List<Card> buyDeck() {
		List<Card> deck = new ArrayList<>(52);
		for (int i = 0; i < 4; i++) {
			for (int j = 1; j <= 13; j++) {
				String suit = SUITS[i];
				int rank = j;
				Card card = new Card();
				card.rank = rank;
				card.suit = suit;
				deck.add(card);
			}
		} 
		return deck;
	}
	private static void swap(List<Card> deck, int i, int j) {
		Card t = deck.get(i);
		deck.set(i, deck.get(j));
		deck.set(j, t);
	}
	private static void shuffle(List<Card> deck) {
		Random random = new Random(20190905);
		for (int i = deck.size() - 1; i > 0; i--) {
			int r = random.nextInt(i);
			swap(deck, i, r);
		}
	}
	public static void main(String[] args) {
		List<Card> deck = buyDeck();
		System.out.println("刚买回来的牌:");
		System.out.println(deck);
		shuffle(deck);
		System.out.println("洗过的牌:");
		System.out.println(deck);
		// 三个人，每个人轮流抓 5 张牌
		List<List<Card>> hands = new ArrayList<>();
		hands.add(new ArrayList<>());
		hands.add(new ArrayList<>());
		hands.add(new ArrayList<>());
		for (int i = 0; i < 5; i++) {
			for (int j = 0; j < 3; j++) {
				hands.get(j).add(deck.remove(0));
			}
		}
 		System.out.println("剩余的牌:");
		System.out.println(deck);
		System.out.println("A 手中的牌:");
		System.out.println(hands.get(0));
		System.out.println("B 手中的牌:");
		System.out.println(hands.get(1));
		System.out.println("C 手中的牌:");
		System.out.println(hands.get(2));
	}
}