Java数据结构之List的使用总结

   public class MyArrayList<E> { 
   private E[] array; 
   private int size;
    ... 
    }

// 定义了一个元素是 Book类 引用的 MyArrayList 
MyArrayList<Book> books = new MyArrayList<Book>(); 
books.add(new Book()); 

// 会产生编译错误，Person 类型无法转换为 Book 类型 
books.add(new Person()); 

// 不需要做类型转换 
Book book = book.get(0); 

// 会产生编译错误，Book 类型无法转换为 Person 类型 
Person person = book.get(0);

import java.util.List;
import java.util.ArrayList;
import java.util.LinkedList;
public class ListDemo {
    public static void main(String[] args) {
        List<String> courses = new ArrayList<>();
        courses.add("Kobe");
        courses.add("Jordan");
        courses.add("Westbrook");
        courses.add("Durant");

        // 和数组一样，允许添加重复元素
        courses.add("Kobe");

        // 按照添加顺序打印
        System.out.println(courses);

        // 类似数组下标的方式访问
        System.out.println(courses.get(0));

        //给目标位置设置新元素
        courses.set(0, "Jordan");
        System.out.println(courses);

        // 截取部分 [1, 3) 注意这里是左开右闭区区间
        List<String> subCourses = courses.subList(1, 3);
        System.out.println(subCourses);

        // 重新构造
        List<String> courses2 = new ArrayList<>(courses);
        System.out.println(courses2);
        List<String> courses3 = new LinkedList<>(courses);
        System.out.println(courses3);

        // 引用的转换
        ArrayList<String> courses4 = (ArrayList<String>)courses2;
        System.out.println(courses4);
        //LinkedList<String> c = (LinkedList<String>)course2; 错误的类型
        LinkedList<String> courses5 = (LinkedList<String>)courses3;
        System.out.println(courses5);
        //ArrayList<String> c = (ArrayList<String>)course3; 错误的类型

        }
    }

import java.util.ArrayList;
import java.util.List;

public class TestDemo {
    public static void main(String[] args) {
        List<Card> deck = CardDemo.buyDeck();
        System.out.println("买来的新牌");
        System.out.println(deck);

        System.out.println("===========================");
        CardDemo.shuffle(deck);
        System.out.println("洗过后的牌");
        System.out.println(deck);
        System.out.println("===========================");

        //三个人，每个人轮流抓牌，一个人五张牌
        List<List<Card>> hands = new ArrayList<>();//二维数组的思维
        hands.add(new ArrayList<>());//加一个人
        hands.add(new ArrayList<>());//再加一个人
        hands.add(new ArrayList<>());//再加一个人，共三个人

        for (int i = 0; i < 5 ; i++){
            for (int j = 0; j < 3; j++){
                hands.get(j).add(deck.remove(0));
                //这里的remove返回顺序表里被移除的元素，刚好牌堆里少一张牌
            }
        }

        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));

    }
}

public class Card {
    private int rank;//牌值
    private String suit;//花色

    public Card(int rank, String suit) {
        this.rank = rank;
        this.suit = suit;
    }

    @Override
    public String toString() {
        return String.format("[%s %d]", suit, rank);
    }
}

import java.util.ArrayList;
import java.util.List;
import java.util.Random;

public class CardDemo {
    private static final String[] suits = {"♥", "♠", "♦", "♣"};

    //买一副牌
    public 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;
                deck.add(new Card(rank, suit));//顺序表默认是尾插
            }
        }
        return deck;
    }

    public static void swap(List<Card> deck, int i, int j) {
        Card temp = deck.get(i);
        deck.set(i, deck.get(j));
        deck.set(j, temp);
    }

    public static void shuffle(List<Card> deck){
        Random rand = new Random(20211122);
        for (int i = deck.size() - 1; i > 0; i--){
            int r = rand.nextInt(i);//生成0~i的随机正整数
            swap(deck, i ,r);
        }
    }