Wednesday, 20 September 2017

How to find the student whose score is greater than 80 using stream and without using stream


Click here to watch in Youtube :
https://www.youtube.com/watch?v=fAAT--78-MI&list=UUhwKlOVR041tngjerWxVccw

Student.java
public class Student implements Comparable<Student> 
{
    private String name;
    private int score;

    public Student(String name, int score)
    {
        this.name = name;
        this.score = score;
    }

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

    public String getName()
    {
        return this.name;
    }

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

    public int getScore()
    {
        return this.score;
    }

    @Override
    public String toString()
    {
        return this.name + " - " + this.score;
    }

    @Override
    public int compareTo(Student another)
    {
        return another.getScore() - this.score;
    }
}
NonStreamDemo.java
import java.util.ArrayList;
import java.util.List;

public class NonStreamDemo
{
    public static void main(String[] args)
    {
        List<Student> studentList = new ArrayList<>();

        studentList.add(new Student("Alice", 82));
        studentList.add(new Student("Bob", 90));
        studentList.add(new Student("Carol", 67));
        studentList.add(new Student("David", 80));
        studentList.add(new Student("Eric", 55));
        studentList.add(new Student("Frank", 49));
        studentList.add(new Student("Gary", 88));
        studentList.add(new Student("Henry", 98));
        studentList.add(new Student("Ivan", 66));
        studentList.add(new Student("John", 52));

        /*
         * Find students whose score >= 80
         */
        List<Student> goodStudentList = new ArrayList<>();
        for (Student student : studentList)
        {
            if (student.getScore() >= 80)
            {
                goodStudentList.add(student);
            }
        }

        for (Student student : goodStudentList)
        {
            System.out.println(student);
        }

        /*
         * Calculate average score of all students
         */
        double sum = 0.0;
        for (Student student : studentList)
        {
            sum += student.getScore();
        }

        double average = sum / studentList.size();

        System.out.println("Average score: " + average);

    }

}
Output
Alice - 82
Bob - 90
David - 80
Gary - 88
Henry - 98
Average score: 72.7

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

public class StreamDemo
{
    public static void main(String[] args)
    {
        List<Student> studentList = new ArrayList<>();

        studentList.add(new Student("Alice", 82));
        studentList.add(new Student("Bob", 90));
        studentList.add(new Student("Carol", 67));
        studentList.add(new Student("David", 80));
        studentList.add(new Student("Eric", 55));
        studentList.add(new Student("Frank", 49));
        studentList.add(new Student("Gary", 88));
        studentList.add(new Student("Henry", 98));
        studentList.add(new Student("Ivan", 66));
        studentList.add(new Student("John", 52));

        /*
         * Find students whose score >= 80
         */
        List<Student> goodStudentList = studentList.stream()
                .filter(s -> s.getScore() >= 80)
                .collect(Collectors.toList());

        goodStudentList.stream().forEach(System.out::println);

        System.out.println("-------------------------------");

        /*
         * Calculate average score of all students
         */
        double average = studentList.stream()
                .mapToInt(s -> s.getScore()).average().getAsDouble();

        System.out.println("Average score: " + average);

        System.out.println("-------------------------------");
        /*
         * Find top 3 students.
         * 
         * As you can see, the operations on a stream can be chained
         * together (intermediate operations) and end with a terminal
         * operation. Such a chain of stream operations is called
         * stream pipeline.
         */
        List<Student> top3Students = studentList.stream()
                .filter(s -> s.getScore() >= 80).sorted().limit(3)
                .collect(Collectors.toList());

        System.out.println("Top 3 Students by Score:");
        top3Students.forEach(s -> System.out.println(s));

    }

}
Output

Alice - 82
Bob - 90
David - 80
Gary - 88
Henry - 98
-------------------------------
Average score: 72.7
-------------------------------
Top 3 Students by Score:
Henry - 98
Bob - 90
Gary - 88

Click the below link to download the code:
https://sites.google.com/site/ramj2eev1/home/javabasics/StreamDemo_Student_score_top3.zip?attredirects=0&d=1

Github Link:
https://github.com/ramram43210/Java/tree/master/BasicJava/StreamDemo_Student_score_top3

Bitbucket Link:
https://bitbucket.org/ramram43210/java/src/adf72ea7a150b1a34af5820c19f2232b522614b9/BasicJava/StreamDemo_Student_score_top3/?at=master

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