接受用户输入并将其添加到数组中

Question

所以我正在重新学习 java 并且已经有一段时间了。我正在尝试构建一个基本程序（在代码 cmets 中进行了解释），但我无法记住如何获取用户输入并将其添加到数组中。我很难记住如何遍历用户输入并测试他们是否输入了任何内容，以及如果他们确实输入了某些内容，则将输入附加到数组中。

//This program will ask user for for there favorite four games
//If the answer is blank, it will ask again for a game title
//The program will than store there answers into an array
//The program will than display the array in random order
//it will then give the amount of games in the array with an integer



import java.util.*;

public class MultipleClassesMain {


public static void main(String[] args) {

    //Array holds 4 string inputs from user
    String gameArray[] = new String[4];

    //importing scanner element-------
    Scanner input = new Scanner(System.in);

    //Introduction---------------
    System.out.println("Hey there!!!");
    System.out.println("Please tell us four game titles you like to play!!!");

    //Asks what game user likes and takes user input into a variable
    System.out.println("So what a game you like?: ");
    String temp = input.nextLine();

    //This loop will test against blank user input
    while (temp.equals("") || (temp.equals("   ")){
        System.out.println("Your game can't be blank.  Enter again: ");

        }

    }

}

这是我到目前为止的代码。如果有人能给我一些建设性的批评和一些关于如何循环用户输入（测试输入）并将输入附加到数组的指示，我将不胜感激。

干杯

Answer 1

首先：使用List 代替数组进行用户输入。只需.add() 您的输入即可。但请参阅下文以获得更好的解决方案，即使用Set。

第二个：String 有一个 .trim() 方法，它可以删除开头和结尾的空格，使用它并使用 .isEmpty() 测试空字符串。

第三：List 不检测重复条目，但 Set 可以，前提是其条目正确实现 equals() 和 hashCode()，String 可以，因此以下代码说明了这一点（ Set 的 .add() 方法当且仅当集合因操作而被修改时才返回 true。

示例代码：

public static void main(final String... args)
{
    // Set of valid user inputs
    final Set<String> gameList = new HashSet<String>();
    // Object from which user inputs are read
    final Scanner in = new Scanner(System.in);

    // Introduction
    System.out.println("Hey there!!");
    System.out.println("Please tell us four game titles you like to play!!!");

    // What the user enters
    String input;

    // Check that 4 titles have been entered, don't get out of the loop until then
    while (gameList.size() < 4) {
        System.out.print("Enter the name of a game: ");
        // Read one input, trim all beginning and trailing whitespaces
        input = in.nextLine().trim();
        // If the resulting string is empty, input is invalid: ask for another
        if (input.isEmpty()) {
            System.out.println("Empty inputs not accepted!");
            continue;
        }
        if (!gameList.add(input))
            System.out.println("You have already selected this game (" + input + ')');
    }

    // Print out the list of inputs
    System.out.println("The list of selected games is: " + gameList);

}

Answer 2

for (int i = 0; i < 4; i++) {
        String temp = input.nextLine();
        if (temp.equals("") || (temp.equals("   "))) {
            System.out.println("Your game can't be blank.  Enter again: ");
            i--;
        } else
            gameArray[i] = temp;

    }

试试这个。这就是你要的……是吗？