目录
一、Collections概述和使用
Collection类的作用:是针对集合操作的工具类
Collection类常用方法:
方法名 | 说明 |
public static void sort(List list) | 将指定的列表按升序排序 |
public static void reverse(List<?> list) | 反转指定列表中元素的顺序 |
public static void shuffle(List<?> list) | 使用默认的随机 |
示例代码:
public class CollectionsDemo01 {
public static void main(String[] args) {
//创建集合对象
List<Integer> list = new ArrayList<Integer>();
//添加元素
list.add(30);
list.add(20);
list.add(50);
list.add(10);
list.add(40);
//public static <T extends Comparable<? super T>> void sort•(List<T> list):将指定的列表按升序排序
Collections.sort(list);
//public static void reverse•(List<?> list):反转指定列表中元素的顺序
Collections.reverse(list);
//public static void shuffle•(List<?> list):使用默认的随机源随机排列指定的列表
Collections.shuffle(list);
System.out.println(list);
}
}
二、ArrayList集合存储学生并排序
需求:
ArrayList存储学生对象,使用Collections对ArrayList进行排序
代码实现:
学生类
public class Student {
private String name;
private int age;
public Student() {
}
public Student(String name, int age) {
this.name = name;
this.age = age;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
}
测试类:
public class CollectionsDemo02 {
public static void main(String[] args) {
//创建ArrayList集合对象
ArrayList<Student> array = new ArrayList<Student>();
//创建学生对象
Student s1 = new Student("linqingxia", 30);
Student s2 = new Student("zhangmanyu", 35);
Student s3 = new Student("wangzuxian", 33);
Student s4 = new Student("liuyan", 33);
//把学生添加到集合
array.add(s1);
array.add(s2);
array.add(s3);
array.add(s4);
//使用Collections对ArrayList集合排序
//sort•(List<T> list, Comparator<? super T> c)
Collections.sort(array, new Comparator<Student>() {
@Override
public int compare(Student s1, Student s2) {
//按照年龄从小到大排序,年龄相同时,按照姓名的字母顺序排序
int num = s1.getAge() - s2.getAge();
int num2 = num == 0 ? s1.getName().compareTo(s2.getName()) : num;
return num2;
}
});
//遍历集合
for (Student s : array) {
System.out.println(s.getName() + "," + s.getAge());
}
}
}
三、斗地主案例
需求:
通过程序实现斗地主过程中的洗牌,发牌和看牌。要求:对牌进行排序
代码实现:
public class PokerDemo {标签:Java,斗地主,ArrayList,list,add,Student,集合,array,public From: https://blog.51cto.com/u_15815415/5738705
public static void main(String[] args) {
//创建HashMap,键是编号,值是牌
HashMap<Integer, String> hm = new HashMap<Integer, String>();
//创建ArrayList,存储编号
ArrayList<Integer> array = new ArrayList<Integer>();
//创建花色数组和点数数组
String[] colors = {"♦", "♣", "♥", "♠"};
String[] numbers = {"3", "4", "5", "6", "7", "8", "9", "10", "J", "Q", "K", "A", "2"};
//从0开始往HashMap里面存储编号,并存储对应的牌。同时往ArrayList里面存储编号
int index = 0;
for (String number : numbers) {
for (String color : colors) {
hm.put(index, color + number);
array.add(index);
index++;
}
}
hm.put(index, "小王");
array.add(index);
index++;
hm.put(index, "大王");
array.add(index);
//洗牌(洗的是编号),用Collections的shuffle()方法实现
Collections.shuffle(array);
//发牌(发的也是编号,为了保证编号是排序的,创建TreeSet集合接收)
TreeSet<Integer> lqxSet = new TreeSet<Integer>();
TreeSet<Integer> lySet = new TreeSet<Integer>();
TreeSet<Integer> fqySet = new TreeSet<Integer>();
TreeSet<Integer> dpSet = new TreeSet<Integer>();
for (int i = 0; i < array.size(); i++) {
int x = array.get(i);
if (i >= array.size() - 3) {
dpSet.add(x);
} else if (i % 3 == 0) {
lqxSet.add(x);
} else if (i % 3 == 1) {
lySet.add(x);
} else if (i % 3 == 2) {
fqySet.add(x);
}
}
//调用看牌方法
lookPoker("林青霞", lqxSet, hm);
lookPoker("柳岩", lySet, hm);
lookPoker("风清扬", fqySet, hm);
lookPoker("底牌", dpSet, hm);
}
//定义方法看牌(遍历TreeSet集合,获取编号,到HashMap集合找对应的牌)
public static void lookPoker(String name, TreeSet<Integer> ts,HashMap<Integer,String> hm) {
System.out.print(name + "的牌是:");
for (Integer key : ts) {
String poker = hm.get(key);
System.out.print(poker + " ");
}
System.out.println();
}
}