Java8 stream collect

package com.stream;

import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;

public class TestStream6 {
    public static void main(String args[]){
        
        List<Stu> students = new ArrayList<Stu>();
        
        students.add(new Stu("Joy",80));
        students.add(new Stu("Joy",90));
        students.add(new Stu("Tony",80));
        students.add(new Stu("Tony",82));
        students.add(new Stu("Joy",85));
        
        List<Stu> stus = students.stream().collect(Collectors.toList());
        System.out.println(stus);
        
        Map<String, List<Stu>> results = students.stream().collect(Collectors.groupingBy(Stu::getName));
        System.out.println(results);
        
    }
}

class Stu{
    int score;
    String name;
    
    Stu(String name,int score){
        this.name = name;
        this.score = score;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getScore() {
        return score;
    }

    public void setScore(int score) {
        this.score = score;
    }
    
}

package com.stream;

import java.util.ArrayList;
import java.util.IntSummaryStatistics;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;

public class TestStream6 {
    public static void main(String args[]){
        
        List<Stu> students = new ArrayList<Stu>();
        
        students.add(new Stu("Joy",80));
        students.add(new Stu("Joy",90));
        students.add(new Stu("Tony",80));
        students.add(new Stu("Tony",82));
        students.add(new Stu("Joy",85));
        
        List<Stu> stus = students.stream().collect(Collectors.toList());
        System.out.println(stus);
        
        Map<String, Long> results = students.stream().collect(Collectors.groupingBy(Stu::getName,Collectors.counting()));
        System.out.println(results);
        
        Map<String, Integer> results2 = students.stream().collect(Collectors.groupingBy(Stu::getName,Collectors.summingInt(Stu::getScore)));
        System.out.println(results2);
        
        Map<String, IntSummaryStatistics> results3 = students.stream().collect(Collectors.groupingBy(Stu::getName,Collectors.summarizingInt(Stu::getScore)));
        System.out.println(results3);
        
    }
}

class Stu{
    int score;
    String name;
    
    Stu(String name,int score){
        this.name = name;
        this.score = score;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getScore() {
        return score;
    }

    public void setScore(int score) {
        this.score = score;
    }
    
}

[com.stream.Stu@eed1f14, com.stream.Stu@7229724f, com.stream.Stu@4c873330, com.stream.Stu@119d7047, com.stream.Stu@776ec8df]
{Tony=2, Joy=3}
{Tony=162, Joy=255}
{Tony=IntSummaryStatistics{count=2, sum=162, min=80, average=81.000000, max=82}, Joy=IntSummaryStatistics{count=3, sum=255, min=80, average=85.000000, max=90}}

int total = students.stream().collect(Collectors.reducing(0,Stu::getScore,(i,j)->i+j));

package com.stream;

import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;

public class TestStream6 {
    public static void main(String args[]){
        
        List<Stu> students = new ArrayList<Stu>();
        
        students.add(new Stu("a",75));
        students.add(new Stu("b",78));
        students.add(new Stu("c",85));
        students.add(new Stu("d",86));
        
    
        
        Map<String, List<Stu>> results = students.stream().collect(Collectors.groupingBy((stu) -> {
            if(stu.getScore()>80){
                return "big";
            }else{
                return "small";
            }
        }));
        
        
        for(String key:results.keySet()){
            List<Stu> s = (List<Stu>) results.get(key);
            System.out.println(key+":"+s.stream().map(Stu::getScore).collect(Collectors.toList()));
        }
    }
}