JJUG Project Lambda Hands-on Materials

FizzBuzz.java

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

public class FizzBuzz {
    private static final String FIZZBUZZ = "FizzBuzz";
    private static final String FIZZ = "Fizz";
    private static final String BUZZ = "Buzz";
    
    public FizzBuzz() {
        List<Integer> numbers = initNumbers();
        
        for (Integer num: numbers) {
            // FizzBuzz の判別処理
            if (num%15 == 0) {
                System.out.println(FIZZBUZZ);
            } else if (num%3 == 0) {
                System.out.println(FIZZ);
            } else if (num%5 == 0) {
                System.out.println(BUZZ);
            } else {
                System.out.println(num);
            }
        }
    }
    
    private List<Integer> initNumbers() {
        List<Integer> numbers = new ArrayList<>();
        for (int i = 0; i <= 100; i++) {
            numbers.add(i);
        }
       
        return numbers;
    }
    
    public static void main(String... args) {
       new FizzBuzz();
    }
}

NumberAdder.java

import java.util.LinkedList;
import java.util.List;
import java.util.functions.Mapper;

public class NumberAdder {
    
    Mapper<List<Integer>, Integer> mapper;

    public NumberAdder() {
        List<Integer> numbers = initNumbers();


        // ここに mapper を使用して numbers の要素の総和を求める処理を書く


        Integer sum = mapper.map(numbers);
        System.out.println(sum);
    }

    private List<Integer> initNumbers() {
        List<Integer> numbers = new LinkedList<>();
        for (int i = 1; i <= 10; i++) {
            numbers.add(i);
        }

        return numbers;
    }

    public static void main(String... args) {
        new NumberAdder();
    }
}

ScoreFinder.java

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

public class ScoreFinder {
    private Random random = new Random();

    public ScoreFinder() {
        List<Student> students = initStudents();
        
        
        // ここに最大の成績を求める処理を記入
        
        
    }
    
    private List<Student> initStudents() {
        List<Student> students = new ArrayList<>();
        for (int i = 0; i <= 5_000_000; i++) {
            students.add(new Student(""+i, random.nextInt(12)+2000, random.nextInt(101)));
        }
        
        return students;
    }
    
    public static void main(String... args) {
        new ScoreFinder();
    }
}

Student.java

public class Student {
    private String name;
    private int gradYear;
    private int score;
 
    public Student(String name, int gradYear, int score) {
        this.name = name;
        this.gradYear = gradYear;
        this.score = score;
    }
 
    public String getName() {
        return name;
    }
 
    public int getGradYear() {
        return gradYear;
    }
 
    public int getScore() {
        return score;
    }

    public String toString() {
	return "["+name+", year:" + gradYear + ", score:" + score + "]";
    }
}

SwingDemo.java

import java.awt.BorderLayout;
import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.SwingUtilities;

public class SwingDemo {
    private JTextField field;
    private JLabel label;

    public SwingDemo() {
        JFrame frame = new JFrame("Swing Demo");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(400, 150);

        JPanel panel = new JPanel();
        panel.setLayout(new FlowLayout(FlowLayout.CENTER, 20, 20));

        field = new JTextField(20);
        panel.add(field);

        JButton button = new JButton("Update");
        panel.add(button);
        frame.add(panel, BorderLayout.NORTH);

        label = new JLabel();
        label.setHorizontalAlignment(JLabel.CENTER);
        frame.add(label, BorderLayout.CENTER);

        ActionListener listener = new ActionListener() {
            public void actionPerformed(ActionEvent event) {
                label.setText(field.getText());
            }
        };
        field.addActionListener(listener);
        button.addActionListener(listener);

        frame.setVisible(true);
    }

    public static void main(String... args) {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                new SwingDemo();
            }
        });
    }
}