一、next()

• 用于从标准输入读取下一个字符串。该方法会扫描输入流并返回下一个非空白字符序列，以空格、制表符或换行符作为分隔符

1、next()会以空格作为分隔符,一行输入1 2 3,只会打印出1

import java.util.Scanner;

public class IOTest {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String input = sc.next();
        System.out.println(input);
    }
}

2、针对输入的一行内容,next()会根据空格、制表符或换行符当成多个输入

import java.util.Arrays;
import java.util.Scanner;

public class IOTest {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String[] str = new String[3];
        for (int i = 0; i < 3; i++){
            str[i] = sc.next();
        }
        System.out.println(Arrays.toString(str));
    }
}

注:nextInt、nextDouble、nextLong等与next()用法类似

二、nextLine()

1、读取一行内容,以换行作为结束

import java.util.Arrays;
import java.util.Scanner;

public class IOTest {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String input = sc.nextLine();
        System.out.println(input);
    }
}

2、会读取next()、nextInt、nextLong后的换行符

import java.util.Arrays;
import java.util.Scanner;

public class IOTest {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String s1 = sc.next();
        String s2 = sc.nextLine();
        System.out.println(s1 + s2);
    }
}

大家可以试一下,这里有两个输入,next()和nextLine(),但是输入ni后程序就会结束,这是因为nextline()读取了next()后的换行符
如何解决呢?

• 只需在next()后再接一行sc.nextLine()读取换行符即可

import java.util.Arrays;
import java.util.Scanner;

public class IOTest {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        String s1 = sc.next();
        sc.nextLine();
        String s2 = sc.nextLine();
        System.out.println(s1 + s2);
    }
}

三、应用

如何实现以下输入?
1、

import java.util.Arrays;
import java.util.Scanner;

public class IOTest {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        while (sc.hasNext()){
            int n = sc.nextInt();
            String[] arrayStr = new String[n];
            Long[] arrayLong = new Long[n];
            for (int i = 0; i < n; i++){
                arrayLong[i] = sc.nextLong();
            }
            for (int i = 0; i < n; i++){
                arrayStr[i] = sc.next();
            }
            System.out.println(Arrays.toString(arrayLong) + " " + Arrays.toString(arrayStr));
        }
    }
}

2、输入一个3 * 3的九宫格

• 放入HashSet中

import java.util.Arrays;
import java.util.HashSet;
import java.util.Scanner;

public class IOTest {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        sc.nextLine();
        HashSet set = new HashSet();
        for (int i = 0; i < n; i++) {
            String line = sc.nextLine();
            String[] str = line.split(" ");
            for (int j = 0; j < str.length; j++){
                set.add(str[j]);
            }
        }
        System.out.println(set.size());
    }
}

• 放在数组中

import java.util.Arrays;
import java.util.HashSet;
import java.util.Scanner;

public class IOTest {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int m = sc.nextInt();
        int n = sc.nextInt();
        sc.nextLine();
        int[][] dp = new int[m][n];
        for (int i = 0; i < m; i++){
            for (int j = 0;j < n; j++){
                dp[i][j] = sc.nextInt();
            }
        }
        for (int i = 0; i < m; i++){
            for (int j = 0; j < n; j++){
                System.out.print(dp[i][j]);
            }
            System.out.println();
        }
    }
}