Java(八)(可变参数,Collections,小案例:斗地主游戏小案例:斗地主游戏,Map集合,Stream流)
目录
可变参数
Collections
小案例:斗地主游戏
Map集合
Map的常用方法
map集合的遍历
键找值
键值对
Lambda 表达式
HashMap底层原理
集合的嵌套
Stream流
获取集合或数组的Stream流
Stream流的方法
可变参数
就是一种特殊的形参,定义在方法和构造器的形参列表中,格式是: 数据类型...参数名称
外部可以接受多个该类型的参数,也可以接收这个参数的数组
而他的内部是一个数组
一个形参列表只能由一个可变参数
可变参数要放到形参列表的后面
public class zheng {
public static void main(String[] args) {
test(); // 不传数据
test(10); // 传一个数据给它
test(10,20,30); // 传输多个数据给他
test(new int[]{10,20,30,40,50}); // 传输一个数组给可变参数
}
public static void test(int...number) {
// 可变参数在方法内部,本质上是一个数组
System.out.println(number.length);
System.out.println(Arrays.toString(number));
System.out.println("---------------------");
}
}
Collections
工具类: 类名.方法 有static修饰的
public class zheng {
public static void main(String[] args) {
// 1.public static boolean addAll(Collection c,T...elements):
// 为集合批量添加数据
List names = new ArrayList<>();
Collections.addAll(names, "张三","王五","李四","张麻子");
System.out.println(names);
// 2.public static void shuffle(List list) 打乱List集合中的元素顺序
Collections.shuffle(names);
System.out.println(names);
// 3.public static void sort(List list) 对List集合中的元素进行升序排序
List list = new ArrayList<>();
list.add(3);
list.add(5);
list.add(2);
Collections.sort(list);
System.out.println(list);
}
} 下面时设置表示方法
// 比较的对象不能排序的时候,那就方法重写
ListStudent = new ArrayList<>();
Student.add(new Student("李小谦",18,100));
Student.add(new Student("李玉刚",58,90));
Student.add(new Student("李德华",48,60));
Collections.sort(Student);
System.out.println(Student);
// 实现接口的匿名内部类
Collections.sort(Student, new Comparator() {
@Override
public int compare(bag5.Student o1, bag5.Student o2) {
return Double.compare(o1.getScore(),o2.getScore());
}
}); 上面的方法1在Student中的实现类是
上面就是相当于用sort方法的时候,给出了Student具体按照什么指标来排序
小案例:斗地主游戏
main类
package bag5;
import org.w3c.dom.ls.LSOutput;
import java.sql.SQLOutput;
import java.util.*;
import java.util.function.Consumer;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class zheng {
public static void main(String[] args) {
// 1.牌类
// 2.房间
// 3.创建一个房间
Room room = new Room();
// 3.启动游戏
room.start();
}
}
创建一个Card类,用来创建Card对象
package bag5;
public class Card {
private String color;
private String number;
private int size;
public Card() {
}
public Card(String color, String number, int size) {
this.color = color;
this.number = number;
this.size = size;
}
@Override
public String toString() {
return color+number;}
public String getColor() {
return color;
}
public void setColor(String color) {
this.color = color;
}
public String getNumber() {
return number;
}
public void setNumber(String number) {
this.number = number;
}
public int getSize() {
return size;
}
public void setSize(int size) {
this.size = size;
}
}
创建一个房间类
package bag5;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
public class Room {
// 必须有一副牌
private List allCards = new ArrayList<>();
List lingHuChong = new ArrayList<>();
List lixiaoqian = new ArrayList<>();
List zhangsanfeng = new ArrayList<>();
public Room()
{
// 1. 做出54张牌,存入集合allCards
// a. 点数: 个数确定,类型确定
String[] numbers = {"3","4","5","6","7","8","9","10","J","Q","K","A","2"};
String[] colors = {"♥","","♣","♦"};
int size = 0;
for(String number: numbers){
size++;
for(String color:colors){
Card c = new Card(number,color,size);
allCards.add(c);
}
}
// 单独存入小大王
Card c1 = new Card("","小王",++size);
Card c2 = new Card("","大王",++size);
Collections.addAll(allCards,c1,c2);
System.out.println(allCards);
}
public void start()
{
// 1. 洗牌: allCards
Collections.shuffle(allCards);
System.out.println("洗牌后: "+ allCards);
// 2. 发牌: 首先定义三个玩家(ArrayList)
for (int i = 0; i < allCards.size() - 3; i++) {
Card c = allCards.get(i);
if (i % 3 == 0)
{
lingHuChong.add(c);
}
else if(i%3 == 1){
lixiaoqian.add(c);
}
else {
zhangsanfeng.add(c);
}
}
// 底牌
List lastTreeCards = allCards.subList(allCards.size() - 3,allCards.size());
//对排进行排序
sortCards(lixiaoqian);
sortCards(lingHuChong);
sortCards(zhangsanfeng);
lixiaoqian.addAll(lastTreeCards);
System.out.println(lixiaoqian);
System.out.println(lingHuChong);
System.out.println(zhangsanfeng);
}
private void sortCards (List cards ){
Collections.sort(cards, new Comparator() {
@Override
public int compare(Card o1, Card o2) {
return o1.getSize() - o2.getSize();
}
});
}
} Map集合
称为双列集合,格式: {key1 = value1,key2=value2}一次需要存一对数据作为一个元素
Map集合的每个元素,"key=value"称为一个键值对/键值对对象/一个Entry对象
Map集合所有键是不允许重复的,但值可以重复,键和值一一对应,每一个键都有自己对应的值
public class map11 {
public static void main(String[] args) {
Map map = new HashMap<>();
map.put("手表",100);
map.put("手表",10);// 后面重复的数据会覆盖前面的数据
map.put("手帕",1200);
map.put("电脑",300);
map.put("手机",500);
System.out.println(map);
}
}
Map的常用方法
public class map11 {
public static void main(String[] args) {
Map map = new HashMap<>();
map.put("手表",100);
map.put("手表",10);// 后面重复的数据会覆盖前面的数据
map.put("手帕",1200);
map.put("电脑",300);
map.put("手机",500);
System.out.println(map);
// 获取集合的大小
System.out.println(map.size());
// 清空
map.clear();
System.out.println();
// 判断是否为空
System.out.println(map.isEmpty());
// 获取键对应的值
int v1 = map.get("手表");
System.out.println(v1);
System.out.println(map.get("手机"));
System.out.println(mao.get("李小谦"));
// public V remove (Object key) 根据键删除整个元素(删除键会返回键的值)
System.out.println(map.remove("手表"));
System.out.println(map);
// public boolean containsKey(Object key) 判断是否包含某个值
System.out.println(map.containsKey("手表"));
System.out.println(map.containsKey("手机"));
System.out.println(map.containsKey("Java"));
System.out.println(map.containsKey("java"));
// public boolean containValue(Object value): 判断是否包含某个键
System.out.println(map.containsValue(100));
// public Set keySet 获取Map集合中全部键
Set set = map.keySet();
System.out.println(set);
// public Collection values() 获取Map集合中的全部值
Collection list = map.values();
System.out.println(list);
// 把其他map数据倒入自己集合中
Mapmap1 = new HashMap<>();
map1.put("java",10);
map1.put("python",100);
Mapmap2 = new HashMap<>();
map2.put("java",20);
map2.put("C++",100);
}
} map集合的遍历
键找值
大体思路就是,将键取出来封装成一个Set对象,然后遍历Set中的键去get到Map中的值
public class map11 {
public static void main(String[] args) {
Map map = new HashMap<>();
map.put("蜘蛛精",162.5);
map.put("蜘蛛精",169.8);
map.put("紫霞",165.8);
map.put("至尊宝",169.5);
map.put("牛魔王",183.6);
System.out.println(map);
// 1. 获取Map集合的全部键
Set keys = map.keySet();
System.out.println(keys);
// 2. 遍历全部的键,根据键获取对应的值
for (String key : keys) {
Double value = map.get(key);
System.out.println(value.doubleValue());
System.out.println(key + "====>" + value);
}
}
} 键值对
将"键值对"看成一个整体进行遍历
public class map11 {
public static void main(String[] args) {
Map map = new HashMap<>();
map.put("蜘蛛精",162.5);
map.put("蜘蛛精",169.8);
map.put("紫霞",165.8);
map.put("至尊宝",169.5);
map.put("牛魔王",183.6);
System.out.println(map);
Set> set= map.entrySet();
for (Map.Entry stringDoubleEntry : set) {
String key = stringDoubleEntry.getKey();
double value = stringDoubleEntry.getValue();
System.out.println(key+ "----->"+ value);
}
}
} Lambda 表达式
public class map11 {
public static void main(String[] args) {
Map map = new HashMap<>();
map.put("蜘蛛精",162.5);
map.put("蜘蛛精",169.8);
map.put("紫霞",165.8);
map.put("至尊宝",169.5);
map.put("牛魔王",183.6);
System.out.println(map);
map.forEach((k,v)->{
System.out.println(k+"---->"+v);
});
map.forEach(new BiConsumer() {
@Override
public void accept(String k, Double v) {
System.out.println(k+"---->"+v);
}
});
}
} HashMap底层原理
集合的嵌套
集合的元素又是一个集合
public class map11 {
public static void main(String[] args) {
Map> map = new HashMap<>();
List cities1 = new ArrayList<>();
Collections.addAll(cities1,"南京市","扬州市","苏州市","无锡市","常州市");
map.put("江苏省",cities1);
List cities2 = new ArrayList<>();
Collections.addAll(cities2,"武汉市","孝感市","宜昌","鄂州市","三峡市");
map.put("湖北省",cities2);
System.out.println(map);
List cities = map.get("湖北省");
for (String city : cities) {
System.out.println(city);
}
map.forEach((p,c)->{
System.out.println(p+"*******"+c);
});
}
} Stream流
获取集合或数组的Stream流
public class map11 {
public static void main(String[] args) {
// 1. 获取ArrayList的stream流
List names = new ArrayList<>();
Collections.addAll(names,"李小谦","李玉刚","张三","罗翔");
Stream stream = names.stream();
// 2.获取Set集合中的Stream流
Set set = new HashSet<>();
Collections.addAll(set , 4,5,6,7,8);
Stream stream1 = set.stream();
stream1.filter(s->(s%2 == 0)).forEach(s-> System.out.println(s));
// 3. 获取Map集合的Stream流
Map map = new HashMap<>();
map.put("古力娜扎",172.6);
map.put("迪丽热巴",175.2);
map.put("欧阳娜娜",173.2);
// map.stream();
// 拿到键的Stream流
Set keys= map.keySet();
Stream ks = keys.stream();
// 拿到值的Stream流
Collection values = map.values();
Stream vs = values.stream();
// 键值对的Stream流
Set> entries = map.entrySet();
Stream> kvs = entries.stream();
kvs.filter(e->e.getKey().contains("巴")).forEach(e-> System.out.println(e.getKey() + "-----" + e.getValue()));
// 数组中的Stream流
String[] names2 = {"张翠山","东方不败","堂大山","独孤九剑"};
Stream s1 = Arrays.stream(names2);
Stream s2 = Stream.of(names2);
}
} Stream流的方法
先设置一个学生类
package bag6;
import java.util.Objects;
public class Student implements Comparable{
// 实现这个结构就是调用排序的时候,排序的方法知道了比较规则
// this o
@Override
public int compareTo(Student o) {
// 如果认为左边对象大于右边对象返回正整数
//如果认为左边对象小于右边对象返回负数
// 如果认为左边等于右边返回0
// this表示调用的,o表示被比较的
return this.age - o.age;
}
private String name;
private int age;
private double Height;
@Override
public String toString() {
return "Student{" +
"name='" + name + '\'' +
", age=" + age +
", Height=" + Height +
'}';
}
// 去重的时候按照值去重,不看hashCode
@Override
public boolean equals(Object o) {
if (this == o) return true;
if (o == null || getClass() != o.getClass()) return false;
Student student = (Student) o;
return age == student.age && Double.compare(student.Height, Height) == 0 && Objects.equals(name, student.name);
}
@Override
public int hashCode() {
return Objects.hash(name, age, Height);
}
public Student() {
}
public Student(String name, int age, double score) {
this.name = name;
this.age = age;
this.Height = score;
}
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;
}
public double getScore() {
return Height;
}
public void setScore(double score) {
this.Height = score;
}
}
常用方法
public class map11 {
public static void main(String[] args) {
List scores = new ArrayList<>();
Collections.addAll(scores,88.5,100.0,60.0,99.0,9.5,99.6);
// 需求1: 找出成绩大于60分的数据,并升序后,再输出
List S = scores.stream().filter(s->s>60).collect(Collectors.toList());
Student s1 = new Student("蜘蛛精",26,172.5);
Student s2 = new Student("蜘蛛精",26,172.5);
Student s3 = new Student("紫霞",23,167.6);
Student s4 = new Student("白晶晶",25,169.0);
Student s5 = new Student("牛魔王",35,183.3);
Collection ls = new ArrayList<>();
Collections.addAll(ls,s1,s2,s3,s4,s5);
// 需求2:找出年龄大于等于23,且年龄小于等于30的学生,并按照年龄降序输出
// List st = ls.stream().filter(s ->s.getAge()>=23 && s.getAge()<=30).sorted(new Comparator() {
// @Override
// public int compare(Student o1, Student o2) {
// return o2.getAge()-o1.getAge();
// }
// }).collect(Collectors.toList());
// System.out.println(st);
// 需求3:取出身高的前三3名学生,并输出
// ls.stream().sorted(new Comparator() {
// @Override
// public int compare(Student o1, Student o2) {
// return Double.compare(o2.getScore(),o1.getScore());
// }
// }).limit(3).forEach(s-> System.out.println(s));
//需求4: 取出身高倒数的2名学生,并输出
// ls.stream().sorted((o1, o2) -> Double.compare(o2.getScore(),o1.getScore()))
// .skip(ls.size()- 2).forEach(s-> System.out.println(s));
// 需求5 : 找出身高超出169的学生叫什么名字,要求去除重复的名字,再输出
ls.stream().filter(s->s.getScore()>168).distinct().forEach(s-> System.out.println(s));
}
} 终结方法
public class map11 {
public static void main(String[] args) {
Student s1 = new Student("蜘蛛精",26,172.5);
Student s2 = new Student("蜘蛛精",26,172.5);
Student s3 = new Student("紫霞",23,167.6);
Student s4 = new Student("白晶晶",25,169.0);
Student s5 = new Student("牛魔王",35,183.3);
Collection ls = new ArrayList<>();
Collections.addAll(ls,s1,s2,s3,s4,s5);
// 需求1:请计算出身高超过168的学生有几个人
long st = ls.stream().filter(s->s.getHeight()>168).count();
System.out.println(st);
// 需求2: 请找出身高最高的学生对象
Optional s = ls.stream()
.max(( o1, o2) ->Double.compare(o1.getHeight() , o2.getHeight()));
System.out.println(s);
// 需求3 : 请找出身高超过170的学生对象,并返回一个新集合中
List student1 = ls.stream().filter(m ->m.getHeight()>170).collect(Collectors.toList());
System.out.println(student1);
// 需求4 : 找出身高超过170的学生对象,并把学生对象名字和身高存到一个Map集合中
Map m1 = ls.stream().filter(q->q.getHeight()>170).distinct()
.collect(Collectors.toMap(w->w.getName(),w->w.getHeight()));
System.out.println(m1);
}
}