如何修复 nextLine 错误以便打印两个单词？ [复制]答案

【问题标题】：How to fix nextLine error so that both words are printed? [duplicate]如何修复 nextLine 错误以便打印两个单词？ [复制]
【发布时间】：2020-01-04 11:57:56
【问题描述】：

下面的代码在运行时运行良好，但如果您在“bands”问题中输入两个单词，您只会得到一个打印回来。

import java.util.Scanner;
public class Main {
  public static void main(String[] args) {
    Scanner scan = new Scanner(System.in);
    System.out.println("What is your name?");
    String name;
    name = scan.next();
    System.out.println("Hello " + name);
    System.out.println("What is your age?");
    int years;
    years = scan.nextInt();
    int ageInMonths;
    ageInMonths = years * 12;
    System.out.print("Your age is ");
    System.out.print(ageInMonths);
    System.out.println(" in months");
    System.out.println("What are your favorite two bands?");
    String bands = scan.next();
    System.out.println("I like >>" + bands + "<<too!");
  }
}

【问题讨论】：

用户 scan.nextLine() instad of next();
如果你使用 scan.nextLine 而不是 next，它不会给你回应的机会
stackoverflow.com/q/13102045/2970947
如链接中的帖子中所述，您必须从以前的读数中删除换行符（请参阅下面的答案）

标签： java

【解决方案1】：

Scanner 类中的方法 next() 将只返回下一个标记。

如 oracle 文档中所写：

从这个扫描器中查找并返回下一个完整的令牌。一种完整的令牌之前和之后是匹配的输入分隔符模式。此方法可能会在等待输入时阻塞扫描，即使之前调用 hasNext() 返回 true。

默认分隔符是空格，所以如果您的乐队名称包含多个单词，它将不起作用。

用于读取整行输入用户nextLine()

如果您想分别拥有两个乐队名称，请致电nextLine() 两次以分别获取每个输入：

System.out.println("What are your favorite two bands?");
String band1 = scan.nextLine();
String band2 = scan.nextLine();
System.out.println("I like >>" + band1 + " and " + band2 + "<<too!");

在这种情况下，用户必须在每次输入后按“输入”。

编辑：

正如 Elliott Frisch 的评论中提到的，其他 readXXX 方法不会从输入流中删除 lineendings。看： stackoverflow.com/q/13102045/2970947

您可以对每个输入使用 nextLine() 或在每次读取后删除换行符。示例代码：

    Scanner scan = new Scanner(System.in);
    System.out.println("What is your name?");
    String name;
    name = scan.next();
    scan.nextLine();
    System.out.println("Hello " + name);
    System.out.println("What is your age?");
    int years;
    years = scan.nextInt();
    scan.nextLine();
    int ageInMonths;
    ageInMonths = years * 12;
    System.out.print("Your age is ");
    System.out.print(ageInMonths);
    System.out.println(" in months");
    System.out.println("What are your favorite two bands?");
    String bands = scan.nextLine();
    System.out.println("I like >>" + bands + "<<too!");

API 参考：

next()

nextLine()

【讨论】：

【解决方案2】：

要获得包含多个单词的完整字符串（直到enter 按下），您应该使用scan.nextLine() 而不是scan.next()（scan.next() 仅用于读取下一个单词）。

不要忘记在 scan.nextInt()and beforescan.nextLine()` 之后添加一个额外的 scan.nextLine()（参见 Java Scanner class reading strings）：

public static void main(String... args) {
    try (Scanner scan = new Scanner(System.in)) {
        System.out.print("What is your name? ");
        String name = scan.nextLine();
        System.out.println("Hello " + name);

        System.out.print("What is your age? ");
        int years = scan.nextInt();
        int ageInMonths = years * 12;
        System.out.println("Your age is " + ageInMonths + " in months");

        System.out.print("What are your favorite two bands? ");
        scan.nextLine();    // extra one after scan.nextInt() - it retrieves a empty string
        String bands = scan.nextLine();
        System.out.println("I like >>" + bands + "<< too!");
    }
}

演示，控制台输出：

What is your name? John Doe
Hello John Doe
What is your age? 666
Your age is 7992 in months
What are your favorite two bands? one two three
I like >>one two three<< too!

【讨论】：