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【Java】標準入力を取得するコードまとめ

Last updated at 2022-09-27Posted at 2022-09-27

環境

paiza.IO

はじめに

この記事では、Javaの標準入力を取得するコードを入力の種類別に紹介する。

nextInt() は状況に応じて nextLong() , nextDouble() 等に変更する。→ メソッド一覧

文字列（1行）

入力例

abc

Scanner.next()

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String str = sc.next();
    }
}

文字列（複数行）

入力例

3
abc
def
ghi

Scanner.next()

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        final int N = sc.nextInt();
        String[] wordArray = new String[N];
      	for(int i = 0; i < N; i++) {
      		wordArray[i] = sc.next();
      	}
    }
}

sc.nextInt() は Integer.parseInt(sc.next())（こちらの方が高速）でも可

半角スペース区切りの文字列（1行）

入力例

abc def ghi

Scanner.nextLine().split(" ")

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String[] wordArray = sc.nextLine().split(" ");
    }
}

Scanner.next()

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        final int N = 3;  // 文字列の数
        String[] wordArray = new String[N];
        for(int i = 0; i < N; i++) {
          wordArray[i] = sc.next();
        }
    }
}

半角スペース区切りの文字列（複数行）

入力例

2 3
abc def ghi
jkl mno pqr

Scanner.next()

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        final int H = sc.nextInt();
        final int W = sc.nextInt();
        String[][] wordArray = new String[H][W];
      	for(int i = 0; i < H; i++) {
        	for(int j = 0; j < W; j++) {
        		wordArray[i][j] = sc.next();
        	}
      	}
    }
}

sc.nextInt() は Integer.parseInt(sc.next())（こちらの方が高速）でも可

Scanner.nextLine().split(" ")

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        final int H = sc.nextInt();
        final int W = sc.nextInt();
        sc.nextLine();
        String[][] wordArray = new String[H][W];
      	for(int i = 0; i < H; i++) {
      	  wordArray[i] = sc.nextLine().split(" ");
      	}
    }
}

sc.nextInt() は Integer.parseInt(sc.next())（こちらの方が高速）でも可

数値（1行）

入力例

Scanner.nextInt()

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
    }
}

Integer.parseInt(Scanner.next())

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = Integer.parseInt(sc.next());
    }
}

数値（複数行）

入力例

Scanner.nextInt()

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        final int N = sc.nextInt();
        int[] numArray = new int[N];
      	for(int i = 0; i < N; i++) {
      		numArray[i] = sc.nextInt();
      	}
    }
}

Integer.parseInt(Scanner.next())

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        final int N = Integer.parseInt(sc.next());
        int[] numArray = new int[N];
      	for(int i = 0; i < N; i++) {
      		numArray[i] = Integer.parseInt(sc.next());
      	}
    }
}

半角スペース区切りの数値（1行）

入力例

100 200 300

Scanner.nextInt()

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        final int N = 3;  // 数値の数
        int[] numArray = new int[N];
    	for(int i = 0; i < N; i++) {
    		numArray[i] = sc.nextInt();
    	}
    }
}

Integer.parseInt(Scanner.next())

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        final int N = 3;  // 数値の数
        int[] numArray = new int[N];
    	for(int i = 0; i < N; i++) {
    	    numArray[i] = Integer.parseInt(sc.next());
    	}
    }
}

Scanner.nextLine().split(" ") + Integer.parseInt()

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        final int N = 3;  // 数値の数
        int[] numArray = new int[N];
        String[] strArray = sc.nextLine().split(" ");
    	for(int i = 0; i < N; i++) {
    		numArray[i] = Integer.parseInt(strArray[i]);
    	}
    }
}

半角スペース区切りの数値（複数行）

入力例

2 3
100 200 300
400 500 600

Scanner.nextInt()

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        final int H = sc.nextInt();
        final int W = sc.nextInt();
        Integer[][] numArray = new Integer[H][W];
      	for(int i = 0; i < H; i++) {
        	for(int j = 0; j < W; j++) {
        		numArray[i][j] = sc.nextInt();
        	}
      	}
    }
}

Integer.parseInt(Scanner.next())

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        final int H = Integer.parseInt(sc.next());
        final int W = Integer.parseInt(sc.next());
        Integer[][] numArray = new Integer[H][W];
      	for(int i = 0; i < H; i++) {
        	for(int j = 0; j < W; j++) {
        		numArray[i][j] = Integer.parseInt(sc.next());
        	}
      	}
    }
}

Scanner.nextLine().split(" ") + Integer.parseInt()

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        final int H = Integer.parseInt(sc.next());
        final int W = Integer.parseInt(sc.next());
        sc.nextLine();
        int[][] numArray = new int[H][W];
        String[] strArray;
      	for(int i = 0; i < H; i++) {
      	    strArray = sc.nextLine().split(" ");
            for(int j = 0; j < W; j++) {
        		numArray[i][j] = Integer.parseInt(strArray[j]);
            }
      	}
    }
}

参考

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