Java

<Java>日付間の日数、週数を取得

import java.time.LocalDate; import java.time.temporal.ChronoUnit; public class Main { public static void main(String[] args) { var date1 = LocalDate.of(1992, 1, 1); var date2 = LocalDate.of(2021, 1, 7); var days = ChronoUnit.DAYS.between(d…

<Java>int[]を降順にソート

import java.util.*; public class Main { public static void main(String[] args) { var numbers = new int[]{ 6, 1, 2, 5, 4, 8, 7, 3, 9 }; System.out.println(Arrays.toString(numbers)); numbers = Arrays.stream(numbers) .boxed() .sorted((n, m) -…

<Java>順位をつける

import java.util.*; public class Sample { public static void main(String[] args) throws Exception { var numbers = new int[]{ 1, 1, 2, 3, 3, 3, 4, 5, 6 }; var ranking = new int[numbers.length]; var rank = 1; ranking[0] = rank; var prev = nu…

<Java>和暦で日付を表示

import java.util.Scanner; import java.util.Locale; import java.time.LocalDate; import java.time.format.DateTimeFormatter; import java.time.chrono.JapaneseDate; import java.time.chrono.JapaneseChronology; public class Main { public static v…

<Java>順列を生成する

import java.util.*; public class Sample { public static void main(String[] args) { var list = new ArrayList<Integer>(); list.add(1); list.add(2); list.add(3); list.add(4); var perm = Permutation.generate(list); perm.forEach(System.out::println); } </integer>…

<Java>組み合わせを作る

import java.util.*; public class Sample { public static void main(String[] args) { var list = new ArrayList<Integer>(); list.add(1); list.add(2); list.add(3); list.add(4); var empty = new ArrayList<Integer>(); var result = new ArrayList<List<Integer>>(); for(var i = 1; i </list<integer></integer></integer>…

<Java>Streamで文字列を編集

public class Sample { public static void main(String[] args) { var string = "123"; var result = string.chars() .map(c -> c - '1' + 'A') .collect(StringBuilder::new, (sb, c) -> sb.append((char)c), StringBuilder::append) .toString(); System.…

<Java>Scannerで一文字ずつ読み込む

import java.util.Scanner; public class Sample { public static void main(String[] args) { var sc = new Scanner(System.in); sc.useDelimiter(""); while(sc.hasNext()) { var c = sc.next(); System.out.print(c); } } }