1：输入字符串统计其中各个字符出现的次数

package java_practice;import java.util.HashMap;import java.util.Scanner;import java.util.Set;//实现一个统计输入字符串中出现某字符的个数public class HashMapDemo2 {    public static void main(String args[]) {        Scanner sc = new Scanner(System.in);        System.out.println("请输入字符串");        String line = sc.nextLine();        //创建HashMap集合        HashMap<Character, Integer> hm = new HashMap<>();        for (int i = 0; i < line.length(); i++) {            char key = line.charAt(i);            Integer value = hm.get(key);            if (value == null) {                hm.put(key, 1);            } else {                value++;                hm.put(key, value);            }        }        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(")");        }        String result = sb.toString();        System.out.println(result);    }}

2：模拟斗地主发牌洗牌

–jgdabc(兰舟千帆)

版本一

package demo;import java.util.ArrayList;import java.util.Collections;import java.util.HashMap;public class PokerDemo {    public static void main(String[] args) {        ArrayList<String> array = new ArrayList<>();        //创建HashMap,键是编号，值是牌        HashMap<Integer, String> hm = new HashMap<>();        //创建ArrayList,存储编号        //定义花色数组        String[] colors = {"", "", "", ""};        String[] numbers = {"2", "3", "4", "5", "6", "7", "8", "9", "10", "J", "Q", "K", "A"};        //        for (String color : colors)            for (String number : numbers) {                array.add(color + number);    }        array.add("小王");        array.add("大王");        //System.out.println(array);        //进行洗牌        Collections.shuffle(array);        // System.out.println(array);        //创建三个玩家        ArrayList<String> lqx = new ArrayList<String>();        ArrayList<String> ly = new ArrayList<>();        ArrayList<String> fqy = new ArrayList<>();        //创建底牌        ArrayList<String> dp = new ArrayList<>();        //进行发牌        for (int i = 0; i < array.size(); i++) {            String s = array.get(i);            if (i >= array.size() - 3) {                dp.add(s);            } else if (i % 3 == 0) {                lqx.add(s);            } else if (i % 3 == 1) {                ly.add(s);            } else if (i % 3 == 2) {                fqy.add(s);            }        }        lookPoker("林青霞",lqx);        lookPoker("柳岩",ly);        lookPoker("风清扬",fqy);        lookPoker("底牌",dp);    }        //看牌的方法        public static void lookPoker(String name,ArrayList<String> array)        {            System.out.print(name + "的牌是:");            for(String poker:array)            {                System.out.print(poker+" ");            }            System.out.println();        }        //存储编号          //    }

版本二

package demo;import java.util.ArrayList;import java.util.Collections;import java.util.HashMap;import java.util.TreeSet;public class PokerDemo1 {    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<>();        //创建花色数组和点数数组        String[] colors = {"", "", "", ""};        String[] numbers = {"2", "3", "4", "5", "6", "7", "8", "9", "10", "J", "Q", "K", "A"};        //从零开始往HashMap中存储编号，并存储对应的牌，同时在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);        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> lqx = new TreeSet<Integer>();        TreeSet<Integer> ly = new TreeSet<Integer>();        TreeSet<Integer> fqy = new TreeSet<Integer>();        TreeSet<Integer> dp = new TreeSet<Integer>();        for (int i = 0; i < array.size(); i++) {            int x = array.get(i);            if (i >= array.size() - 3) {                dp.add(x);            } else if (i % 3 == 0) {                lqx.add(x);            } else if (i % 3 == 1) {                ly.add(x);            } else if (i % 3 == 2) {                fqy.add(x);            }        }        lookPoker("林青霞", lqx, hm);        lookPoker("柳岩", ly, hm);        lookPoker("风清扬",fqy,hm);        lookPoker("底牌",dp,hm);    }    //定义方法看牌（遍历TreeSet集合，获取编号，到HashMap找到对应的牌）    public static void lookPoker(String name, TreeSet<Integer> ts, HashMap<Integer, String> hm) {        System.out.println(name + "的牌是：");        for (Integer key : ts) {            String poker = hm.get(key);            System.out.print(poker + " ");        }        System.out.println();    }}