一、將單詞統計出來
package mypro01;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;

//分揀儲存--》分類歸類
public class MapDemo01 {
	public static void main(String[] args) {
		//分割字串
		String[] arr="this is a cat and that is a nice is dang jing is ".split(" ");
		//分揀儲存
		Map<String,Integer> map=new HashMap<String,Integer>();
		
		for(String key:arr) {
			if(!map.containsKey(key)) {
				map.put(key, 1);
			}else {
				map.put(key, map.get(key)+1);
			}
		}
		//檢視每個單詞出現的次數
		Set<String> ketSet = map.keySet();
		Iterator<String> it = ketSet.iterator();
		while(it.hasNext()) {
			String key = it.next();
			Integer value=map.get(key);
			System.out.println("key:"+key+"----->value:"+value);
		}
		
	}
	
	
}
 

二、面向物件儲存

package mypro01;

public class Student {
    private     String name;
    private  String id;
    private  double score;
    
    public Student(String name, String id, double score) {
        super();
        this.name = name;
        this.id = id;
        this.score = score;
    }
    
 
public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getId() {
        return id;
    }
    public void setId(String id) {
        this.id = id;
    }
    public double getScore() {
        return score;
    }
    
 
public void setScore(double score) {
        this.score = score;
    }
    
    
}

package mypro01;

import java.util.ArrayList;
import java.util.List;

public class ClassRoom {
    private String no;
    private List<Student> stuList;
    private double total;
    public ClassRoom(String no, List<Student> stuList, double total) {
        super();
        this.no = no;
        this.stuList = stuList;
        this.total = total;
    }
    public String getNo() {
        return no;
    }
    public void setNo(String no) {
        this.no = no;
    }
    public List<Student> getStuList() {
        return stuList;
    }
    public void setStuList(List<Student> stuList) {
        this.stuList = stuList;
    }
    public double getTotal() {
        return total;
    }
    public void setTotal(double total) {
        this.total = total;
    }
    public ClassRoom() {
        stuList=new ArrayList<Student>();
        
    }
    public ClassRoom(String no) {
        this();
        this.no=no;
    }
}

package mypro01;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Set;

public class MapDemo02 {
    public static void main(String[] args) {
        //靠手
        List<Student> stulist=exam();
        Map<String,ClassRoom> map=count(stulist);
        view(map);
    }
    //計算分數
    public static void view(Map<String,ClassRoom> map) {
        Set<String> keyset=map.keySet();
        Iterator<String> itkey=keyset.iterator();
        while(itkey.hasNext()) {
            String no=itkey.next();
            ClassRoom room=map.get(no);
            double total=room.getTotal();
            double avg=total/room.getStuList().size();
            System.out.println(no+"--->"+total+"--->"+avg);
        }
    }
    
    //分類
    public static Map<String,ClassRoom> count(List<Student> list){
        Map<String,ClassRoom> map=new HashMap<String,ClassRoom>();
        for(Student stu:list) {
            String no=stu.getId();
            double score=stu.getScore();
            ClassRoom room=map.get(no);
            if(null==room) {
                room =new ClassRoom(no);
                map.put(no, room);
            }
            
            room.getStuList().add(stu);
            room.setTotal(room.getTotal()+score);
        }
        
        return map;
    }
    
    //模擬考試成績到其中
    public static List<Student> exam(){
        List<Student> list=new ArrayList<Student>();
        
        list.add(new Student("張三","1",80));
        list.add(new Student("李四","2",40));
        list.add(new Student("王五","1",44));
        list.add(new Student("馬六","2",22));
        list.add(new Student("馬2","3",22));
        
        return list;
    }
}

結果：
1--->124.0--->62.0
2--->62.0--->31.0
3--->22.0--->22.0