Java集合的互相嵌套以及TreeMap集合获取字符串中不同字符数量实例
文章目录
1、获取输入字符串中每个字符的个数
package test12_TreeMap;
import java.util.Scanner;
import java.util.Set;
import java.util.TreeMap;
/*
* 功能：获取输入字符串中每个字符的个数，并输出
* 思路： 1、接收字符串
* 2、转化为字符数组
* 3、使用TreeMap集合（键为字符，值为字符出现的次数）
* 首先看集合中是否含有此字符
* 没有则添加新的键值对（字符，1）
* 有则更改值并存储（字符，++次数）
* 4、增强for遍历TreeMap集合并按照指定格式进行存储
*
*/
public class TreeMap_Demo {
public static void main(String[] args) {
Scanner sc=new Scanner(System.in);
System.out.println("请输入字符串");
String s=sc.nextLine();
sc.close();
char []c=s.toCharArray();
TreeMap<Character,Integer> tm=new TreeMap<Character,Integer>();
for(char ch: c) {
Integer i=tm.get(ch);
if(i==null) {
tm.put(ch, 1);
}else {
tm.put(ch, ++i);
}
}
StringBuilder sb=new StringBuilder();
Set<Character> set=tm.keySet();
for(Character ch:set) {
int i=tm.get(ch);
//字符串拼接
sb.append(ch).append("出现").append(i).append("次,");
}
System.out.println(sb);
}
}
输出结果：
2、ArrayList嵌套HashMap
package test13_Nest;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Set;
/*
* ArrayList嵌套HashMap
*
* 一共有两组HashMap
* 小明-踢球
* 小王-游泳
*
* 小红-唱歌
* 小丽-画画
*/
public class ArrayListNestHashMap {
public static void main(String[] args) {
ArrayList<HashMap<String,String>> al=new ArrayList<HashMap<String,String>>();
HashMap<String,String> hm1=new HashMap<String,String>();
HashMap<String,String> hm2=new HashMap<String,String>();
hm1.put("小明", "踢球");
hm1.put("小王", "游泳");
hm2.put("小红", "小红");
hm2.put("小丽", "画画");
al.add(hm1);
al.add(hm2);
for(HashMap<String,String> hm:al) {
Set <String> set=hm.keySet();
for(String key:set) {
String value=hm.get(key);
System.out.println(key+"--"+value);
}
}
}
}
输出结果
3、HashMap嵌套ArrayList
package test13_Nest;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Set;
/*
* 实现HashMap嵌套ArrayList
* man
* 小明
* 小王
* woman
* 小红
* 小丽
*/
public class HashMapNestArrayList {
public static void main(String[] args) {
HashMap<String,ArrayList<String>> hm=new HashMap<String,ArrayList<String>>();
ArrayList<String> al1=new ArrayList<String>();
al1.add("小明");
al1.add("小王");
ArrayList<String> al2=new ArrayList<String>();
al2.add("小红");
al2.add("小丽");
hm.put("man", al1);
hm.put("woman", al2);
Set<String> set=hm.keySet();
for(String key:set) {
ArrayList<String> value=hm.get(key);
System.out.println(key);
for(String s:value) {
System.out.println("\t"+s);
}
}
}
}
输出结果
4、HashMap嵌套HashMap
package test13_Nest;
import java.util.HashMap;
import java.util.Set;
/*
* 实现HashMap嵌套HashMap
* 键 值 键 值
* Man 男人Map :
* 1、 小明 20
* 2、 小王 22
* Woman 女人Map：
* 1、 小红 18
* 2、 小丽 16
*/
public class HashMapNestHashMap {
public static void main(String[] args) {
//创建HashMap对象
HashMap<String,HashMap<String,Integer>> peopleMap=new HashMap<String,HashMap<String,Integer>>();
HashMap<String,Integer> manMap=new HashMap<String,Integer>();
HashMap<String,Integer> womanMap=new HashMap<String,Integer>();
//添加元素
manMap.put("小明", 20);
manMap.put("小王", 22);
peopleMap.put("man", manMap);
womanMap.put("小红", 18);
womanMap.put("小丽", 16);
peopleMap.put("woman", womanMap);
//遍历
Set <String> peopleMapSet=peopleMap.keySet();
for(String peopleMapKey:peopleMapSet) {
HashMap<String,Integer> peopleMapValue=peopleMap.get(peopleMapKey);
System.out.println(peopleMapKey);
Set<String> peopleMapValueSet=peopleMapValue.keySet();
for(String peopleMapValueKey:peopleMapValueSet) {
Integer peopleMapValueValue=peopleMapValue.get(peopleMapValueKey);
System.out.println("\t"+peopleMapValueKey+":"+peopleMapValueValue);
}
}
}
}
输出结果
5、HashMap嵌套HashMap再嵌套ArrayList
三层嵌套，ArrayList存储的是学生对象
嵌套程序
package test13_Nest;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Set;
/*
* 实现三层嵌套：HashMap嵌套HashMap再嵌套ArrayList
* 这次的ArrayList存储的是学生对象
*
* 通信学院：
* 2班
* 小红18岁
* 小李18岁
* 12班
* 小王19岁
* 小丽18岁
* 电子学院：
* 1班
* 小芳18岁
* 小明20岁
* 11班
* 小赵20岁
* 小军19岁
*/
public class ThreeNest {
public static void main(String[] args) {
HashMap<String,HashMap<String,ArrayList<Student>>> hm=
new HashMap<String,HashMap<String,ArrayList<Student>>>();
HashMap<String,ArrayList<Student>> hm1=new HashMap<String,ArrayList<Student>>();
HashMap<String,ArrayList<Student>> hm2=new HashMap<String,ArrayList<Student>>();
ArrayList<Student> a1=new ArrayList<Student>();
ArrayList<Student> a2=new ArrayList<Student>();
ArrayList<Student> a3=new ArrayList<Student>();
ArrayList<Student> a4=new ArrayList<Student>();
Student s1=new Student("小红",18);
Student s2=new Student("小李",18);
Student s3=new Student("小王",19);
Student s4=new Student("小丽",18);
Student s5=new Student("小芳",18);
Student s6=new Student("小明",20);
Student s7=new Student("小赵",20);
Student s8=new Student("小军",19);
a1.add(s1);
a1.add(s2);
a2.add(s3);
a2.add(s4);
a3.add(s5);
a3.add(s6);
a4.add(s7);
a4.add(s8);
hm1.put("2班", a1);
hm1.put("12班", a2);
hm2.put("1班", a3);
hm2.put("11班", a4);
hm.put("通信学院", hm1);
hm.put("电子学院", hm2);
Set <String> hmSet=hm.keySet();
for(String hmKey: hmSet) {
HashMap<String,ArrayList<Student>> hmValue=hm.get(hmKey);
System.out.println(hmKey);
Set<String> hmValueSet=hmValue.keySet();
for(String hmValueKey:hmValueSet) {
ArrayList<Student> hmValueValue=hmValue.get(hmValueKey);
System.out.println("\t"+hmValueKey);
for(Student al:hmValueValue) {
System.out.println("\t\t"+al.getName()+al.getAge()+"岁");
}
}
}
}
}
学生类程序
package test13_Nest;
public class Student {
private String name;
private int age;
public Student() {
super();
// TODO Auto-generated constructor stub
}
public Student(String name, int age) {
super();
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;
}
}
输出结果