JAVA之Collects概述及其两个例子

针对集合操作的工具类
sort(List l)：将指定的列表按升序排序
reverse(List l)：反转指定列表中元素的顺序
shuffle(List l):使用默认的随机源随机排列指定的列表

统计字符串

package Map集合.统计字符串的数量;

import java.util.HashMap;
import java.util.Scanner;
import java.util.Set;

public class CollectionChar {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
     Scanner sc=new Scanner(System.in);
     System.out.println("请输入一个字符串");
     String line=sc.nextLine();
     //TreeSet排序
     HashMap<Character, Integer> hm=new HashMap<Character, Integer>();
     //遍历字符串
      for(int i=0;i<line.length();i++) {
    	  char key=line.charAt(i);
    //取得key去找HashMap中找值
    	  Integer value=hm.get(key);
    //如果不存在就记为1，存在就+1并且重新存储
    	  if(value==null) {
    		  hm.put(key, 1);
    	  }else {
    		  value++;
    		  hm.put(key, value);
    	  }
      }
      //遍历HashMap集合，得到键和值
      StringBuilder sb=new StringBuilder();
      Set<Character> keyset=hm.keySet();
      for(Character key:keyset) {
    	  Integer value=hm.get(key);
    	  sb.append(key).append("(").append(value).append(")");
      }
      
      System.out.println(sb.toString());
	}

}

模拟斗地主

package Map集合.斗地主;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.TreeSet;

public class PokerDemo {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
     //创建HashMap,键是牌号，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，并且存储对应编号，同时往ArrayLiat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, "小王");
		array.add(index);
		//洗牌(洗的是编号)
		Collections.shuffle(array);
		//发牌(发的也是编号，为了保证编号是排序的，采用TreeSet接受
		TreeSet<Integer> t1=new TreeSet<Integer>();
		TreeSet<Integer> t2=new TreeSet<Integer>();
		TreeSet<Integer> t3=new TreeSet<Integer>();
		TreeSet<Integer> dipai=new TreeSet<Integer>();
		for(int i=0;i<array.size();i++) {
			int x=array.get(i);
			if(i>=array.size()-3) {
				dipai.add(x);
			}else if(i % 3==0) {
				t1.add(i);
			}
			else if(i % 3==1) {
				t2.add(i);
			}
			else if(i % 3==2) {
				t3.add(i);
			}
		}
		lookPoker("张三1", t1, hm);
		lookPoker("张三2", t2, hm);
		lookPoker("张三3", t3, hm);
		lookPoker("底牌", dipai, hm);
	}
      public static void lookPoker(String name,TreeSet<Integer> ts,HashMap<Integer, String> hs) {
    	  System.out.print(name+"的牌是：");
    	  for(Integer key:ts) {
    		  String poker=hs.get(key);
    		  System.out.print(poker+" ");
    	  }
    	 System.out.println();
      }
}