【備忘録】Javaの変数宣言と同時に初期化、ストリームAPIでソート

備忘録

TEST.java

import java.util.ArrayList;
import java.util.Comparator;
import java.util.TreeMap;
import java.util.stream.Collectors;

public class TEST {
    private record Point(String no1, String no2, String value) {
    }

    public static void main(String[] args) {
        // 初期化
        var btree = new TreeMap<String, String>() {
            {
                put("2011-2", "1");
                put("2011-1", "1");
                put("2012-2", "1");
                put("2012-1", "1");
                put("2024-2", "1");
                put("2024-1", "1");
            }
        };
        for (var m : btree.entrySet()) {
            System.out.println(m.getKey() + ", " + m.getValue());
        }

        // 初期化
        var input = new ArrayList<Point>() {
            {
                add(new Point("2011", "2", "1"));
                add(new Point("2011", "1", "1"));
                add(new Point("2012", "2", "1"));
                add(new Point("2012", "1", "1"));
                add(new Point("2024", "2", "1"));
                add(new Point("2024", "1", "1"));
            }
        };
        var sorted = input
                .stream()
                .sorted(Comparator.comparing(Point::no1).thenComparing(Point::no2))
                .collect(Collectors.toList());

        for (var m : sorted) {
            System.out.println(m.no1() + ", " + m.no2() + ", " + m.value());
        }
    }
}

2011-1, 1
2011-2, 1
2012-1, 1
2012-2, 1
2024-1, 1
2024-2, 1
2011, 1, 1
2011, 2, 1
2012, 1, 1
2012, 2, 1
2024, 1, 1
2024, 2, 1