0 Sorting Chart:
1 HashMap(key, MyBean(key, number of occurrences))
class Letter {
private String name;
private int count;
public Letter() {
// TODO Auto-generated constructor stub
}
public Letter(String name, int count) {
super();
this.name = name;
this.count = count;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getCount() {
return count;
}
public void setCount(int count) {
this.count = count;
}
}
/**
* this is a cat and that is a mice and where is the food?
* Count the number of times each word appears
*
* Store in Map
* key :String
* value: custom type
*
* "sorting" idea
* 1. Create containers for all keys
* After that, the corresponding value is stored in the container
* 2. Create the container for the first time and store the value value
* After the second time, use the container directly to store the value
* @author Administrator
*
*/
public class Demo01 {
/**
* @param args
*/
public static void main(String[] args) {
String str ="this is a cat and that is a mice and where is the food";
// split the string
String[] strArray=str.split(" ");
// store in Map
Map<String,Letter> letters = new HashMap<String,Letter>();
for(String temp:strArray){
/*
//1. Create a container for all keys
if(!letters.containsKey(temp)){
Letter col = new Letter();
col.setCount(1); //The first value is stored in the container
letters.put(temp, col);
}else{
//2. After the second time, directly use the container to store the value
Letter col =letters.get(temp); //Use the container directly
col.setCount(col.getCount()+1);
}*/
Letter col = null;
if(null==(col=letters.get(temp))){ //This extraction is quite interesting
col = new Letter();
col.setCount(1); //The first value is stored in the container
letters.put(temp, col);
}else{
//2. After the second time, directly use the container to store the value
col.setCount(col.getCount()+1);
}
}
// output the value of the map
Set<String> keys = letters.keySet();
for(String key:keys){
Letter col =letters.get(key);
System.out.println("Letter:"+key+",Number of times"+col.getCount());
}
}
public static void test1(){
String str ="this is a cat and that is a mice and where is the food";
// split the string
String[] strArray=str.split(" ");
// store in Map
Map<String,Letter> letters = new HashMap<String,Letter>();
/*
for(String temp:strArray){
//1. Create a container for all keys
Then the corresponding value is stored in the container
if(!letters.containsKey(temp)){
letters.put(temp, new Letter());
}
}
for(String temp:strArray){
// Store the corresponding value in the container
Letter col =letters.get(temp); //Use the container directly
col.setCount(col.getCount()+1);
}
*/
for(String temp:strArray){
//1. Create a container for all keys
if(!letters.containsKey(temp)){
letters.put(temp, new Letter());
}
//2, then store the corresponding value in the container
Letter col =letters.get(temp); //Use the container directly
col.setCount(col.getCount()+1);
}
// output the value of the map
Set<String> keys = letters.keySet();
for(String key:keys){
Letter col =letters.get(key);
System.out.println("Letter:"+key+",Number of times"+col.getCount());
}
}
}
2 Count the average score of the class, pay attention to the encapsulation of the classroom in the value (object-oriented encapsulation) HashMap(classno, ClassRoom(classno,studentLists,totalScore))
public class Student {
private String name;
private String no;
private double score;
public Student() {
}
public Student(String name, String no, double score) {
super();
this.name = name;
this.no = no;
this.score = score;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getNo() {
return no;
}
public void setNo(String no) {
this.no = no;
}
public double getScore() {
return score;
}
public void setScore(double score) {
this.score = score;
}
@Override
public String toString() {
return "Student [name=" + name + ", no=" + no + ", score=" + score
+ "]";
}
}
/**
* class
* @author Administrator
*
*/
public class ClassRoom {
private String no;
private List<Student> stus; //student list
private double total; //Total score
public ClassRoom() {
stus = new ArrayList<Student>();
}
public ClassRoom(String no) {
this();
this.no = no;
}
public String getNo() {
return no;
}
public void setNo(String no) {
this.no = no;
}
public List<Student> getStus() {
return stus;
}
public void setStus(List<Student> stus) {
this.stus = stus;
}
public double getTotal() {
return total;
}
public void setTotal(double total) {
this.total = total;
}
}
/**
* Define a Student class, attributes: name name, classNumber class number, score
Now put several Student objects into the List, please count the total score and average score of each class, and print them out respectively
object-oriented thinking
* @author Administrator
*
*/
public class MapDemo03 {
public static void main(String[] args) {
List<Student> list = new ArrayList<Student>();
exam(list);
//statistics
Map<String,ClassRoom> rooms = new HashMap<String,ClassRoom>();
count(rooms,list);
//Print
printScore(rooms);
}
/**
* Print the total and average scores
*/
public static void printScore(Map<String,ClassRoom> rooms){
Set<Map.Entry<String,ClassRoom>> entrySet =rooms.entrySet();
Iterator<Map.Entry<String,ClassRoom>> it =entrySet.iterator();
while(it.hasNext()){
Map.Entry<String,ClassRoom> entry =it.next();
ClassRoom room = entry.getValue();
double avg = room.getTotal()/room.getStus().size();
System.out.println("The class number is: "+room.getNo()+", the total score is "+room.getTotal()+", the average score is "+avg);
}
}
/**
* Statistics score
*/
public static void count(Map<String,ClassRoom> rooms,List<Student> list){
for(Student stu:list){
String no = stu.getNo();
double score = stu.getScore();
//Check if there is a class sorting idea in the Map according to the class number
ClassRoom room = rooms.get(no);
if(null==room){ //First time
room = new ClassRoom(no);
rooms.put(no, room);
}
// store the total score
room.setTotal(room.getTotal()+score);
room.getStus().add(stu); //Add students
}
}
/**
* Now put several Student objects into List
* @param list
*/
public static void exam(List<Student> list){
list.add(new Student("a","001",80));
list.add(new Student("b","001",80));
list.add(new Student("a","002",80));
list.add(new Student("c","003",80));
list.add(new Student("d","003",80));
}
}