【JavaSE】作业练习1118

1、请编写程序，统计一个字符串中每个字符出现的次数

import java.util.HashMap;import java.util.Scanner;public class Demo1 {    public static void main(String[] args) {        Scanner sc=new Scanner(System.in);        System.out.println("请输入一串字符串");        String s=sc.nextLine();        HashMap <Character,Integer>hm=new HashMap<Character,Integer>();        char[] ch = s.toCharArray();        for(char c:ch){            Integer value = hm.get(c);            if(value==null){                hm.put(c,1);            }else{                value++;                hm.put(c, value);            }        }        System.out.println(hm);    }}

2、请编写程序，存储自定义对象到HashMap集合中，并采用两种方式遍历

import java.util.HashMap;import java.util.Map.Entry;import java.util.Set;public class Demo2 {    public static void main(String[] args) {        HashMap<Student, Integer> hm = new HashMap<Student,Integer>();        hm.put(new Student("张三",15), 1);        hm.put(new Student("李四",20), 2);        hm.put(new Student("王五",16), 3);        hm.put(new Student("赵六",18), 4);        System.out.println(hm);        //方式一        Set<Student> key = hm.keySet();        for(Student s:key){            System.out.println("键为："+s+"\t值为："+hm.get(s));        }        //方式二        Set<Entry<Student, Integer>> entrySet = hm.entrySet();        for(Entry e:entrySet){            System.out.println("键为："+e.getKey()+"值为："+e.getValue());        }    }}

3、请编写程序，存储自定义对象到TreeMap集合中，并采用两种方式遍历

import java.util.Map.Entry;import java.util.Set;import java.util.TreeMap;public class Demo3 {    public static void main(String[] args) {        TreeMap<Person, String> tree = new TreeMap<Person,String>();        tree.put(new Person("张三",45),"北京市" );        tree.put(new Person("李四",23),"上海市" );        tree.put(new Person("王五",67),"北京市" );        tree.put(new Person("赵六",36),"南京市" );        System.out.println(tree);        //方式一        Set<Person> keySet = tree.keySet();        for(Person p:keySet){            System.out.println("键为："+p+"\t值为："+tree.get(p));        }        //方式二        Set<Entry<Person, String>> entrySet = tree.entrySet();        for(Entry e:entrySet){            System.out.println("键为："+e.getKey()+"\t值为："+e.getValue());        }    }}

4、请编写程序，完成集合嵌套,并遍历
　　jc　　基础班
　　　　　　张三 20
　　　　　　李四 22
　　jy　　就业班
　　　　　　王五 21
　　　　　　赵六 23
HashMap嵌套HashMap

import java.util.HashMap;import java.util.Set;public class Demo4 {    public static void main(String[] args) {        HashMap<String, Integer> jc = new HashMap<String,Integer>();        jc.put("张三", 20);        jc.put("李四", 22);        HashMap<String, Integer> jy = new HashMap<String,Integer>();        jy.put("王五", 21);        jy.put("赵六", 23);        HashMap<HashMap<String, Integer>, String> big = new HashMap<HashMap<String, Integer>,String>();        big.put(jc, "基础班");        big.put(jy,"就业班");        Set<HashMap<String, Integer>> bigKey = big.keySet();        for(HashMap<String, Integer> hm:bigKey){            Set<String> key = hm.keySet();            System.out.println(big.get(hm));            for(String s:key){                System.out.println("\t"+s+"\t"+hm.get(s));            }        }    }}

HashMap嵌套ArrayList

import java.util.ArrayList;import java.util.HashMap;import java.util.Set;public class Demo5 {    public static void main(String[] args) {        ArrayList<Student> jc = new ArrayList<Student>();        jc.add(new Student("张三", 20));        jc.add(new Student("李四", 22));        ArrayList<Student> jy = new ArrayList<Student>();        jy.add(new Student("王五", 21));        jy.add(new Student("赵六", 23));        HashMap<ArrayList<Student>,String> arrayList = new HashMap<ArrayList<Student>,String> ();        arrayList.put(jc,"基础班");        arrayList.put(jy,"就业班");        Set<ArrayList<Student>> keySet = arrayList.keySet();        for(ArrayList<Student> arr:keySet){            System.out.println(arrayList.get(arr));            for(Student s:arr){                System.out.println("\t"+s);            }        }    }}

5、生成扑克牌并模拟洗牌

import java.util.ArrayList;import java.util.Collections;public class Demo6 {    public static void main(String[] args) {        ArrayList<String> pokerBox = new ArrayList<String>();        String[] colors = { "♥", "♠", "♦", "♣" };        String[] nums = { "A", "2", "3", "4", "5", "6", "7", "8", "9", "10", "J", "Q", "K" };        for (String color : colors) {            for (String num : nums) {                pokerBox.add(color + num);            }        }        //添加大王小王        pokerBox.add("大王");        pokerBox.add("小王");        //洗牌        Collections.shuffle(pokerBox);        Collections.shuffle(pokerBox);        Collections.shuffle(pokerBox);    }}