Question

在我开始之前，我想说;我之前已经问过这个问题，并且被我改变程序的方式所淹没，而不是我的问题的明确答案 - 我很满意我的代码我只想验证它：）

就像标题暗示我试图验证我的字符串数组一样，我是Java新手并且一直试图在for循环中放置几个布尔条件但是代码似乎总是忽略循环并继续正常运行，例如我写＆＃34; if（words == null）print＆＃34; Error＆＃34;＆＃34;程序正常运行，就好像条件不存在，即使数组位置为空。

String [] football_list = new String [100];         //Declare the array 
int counter = 0;                                //Initialize counter integer

scanner = new Scanner(System.in);{      //Import Scanner
System.out.println("Input as follows; "); {     //User instructions
System.out.println("Home team : Away team : Home score : Away score");

String line = null; { // Creates a blank string

while (!(line = scanner.nextLine()).equals("")) { // The code in the loop will process only if it is not empty

    if (line.equals("quit")) { // When the user is finished this exits the program
           break;
    } else {
        football_list[counter] = line; // The below String is printed for the amount of values inside the counter integer

        System.out.println("Home team : Away team : Home score : Away score");
    }

    counter++;  // counter is incremented
}

}
for (int i = 0; i < counter; i++) { // A loop to control the Array 
    String[] words = football_list[i].split(":"); // Splits the input into 4 strings
    if(words.equals(null)){

        System.out.println("Null");
        }
    else
    System.out.println(words[0].trim() + " [" + words[2].trim() + "]" + " | " + words[1].trim() + " [" + words[3].trim() + "]"); // Formats and prints the output    

    }



}
    }
        }
            }

我的代码根据用户输入创建了一个运动结果表。用户输入这样的输入＆＃34; Home_Team：Away_Team：Home_Score：Away_Score＆＃34;，我想生成一条错误消息，并在其中一个插槽为空时停止该程序。

新错误

for (int i = 0; i < counter; i++) { // A loop to control the Array 
    String[] words = football_list[i].split(":"); // Splits the input into 4 strings
    if (words.length != 4) { // If the length of the array elements does not equal 4 then print error message
        System.out.println("Input was not valid");
        //counter--;
        //i--;
    } else
    {

    System.out.println(words[0].trim() + " [" + words[2].trim() + "]" + " | " + words[1].trim() + " [" + words[3].trim() + "]"); // Formats and prints the output    


   }
   }
   }
    System.out.println("                 ");
    System.out.println("                 ");
    System.out.println("                 ");
    System.out.println("        Totals        ");
    System.out.println("-------------------------");
    System.out.println("Total games played: " +  counter);


    }

Answer 1

如果您尝试检测

等输入

Tigers:Lions:7

找出words的长度并检查它是否为4。

if (words.length != 4){

    System.out.println("Input was not valid.");
}
else{
    // Print formatted string 
}

另一方面，请确保您了解空数组/字符串和空数组/字符串不相同。空数组{}或空字符串“”有一个值，即使它是空的。

String[] words = football_list[i].split(":"); // Splits the input into 4 strings
if(words.equals(null)){
    System.out.println("Null");
}

此处words永远不会是null，因为您已将其初始化为football_list[i].split(":")。另外，请注意它也永远不会是空数组。

如果在:中找不到football_list[i]，则数组将包含一个元素words[0] = football_list[i]。

将某些内容初始化为null没有用，因为String line;已经line为null。

完整代码应该类似于：

import java.util.Scanner;

public class circle {
    public static void main(String[] args) {
        String[] football_list = new String[100]; // Declare the array
        int counter = 0; // Initialize counter integer

        Scanner scanner = new Scanner(System.in); // Import Scanner
        System.out.println("Input as follows; "); // User instructions
        System.out.println("Home team : Away team : Home score : Away score");

        String line = null; // Creates a blank string

        while (!(line = scanner.nextLine()).equals("")) { // The code in the
                                                        // loop will process
                                                        // only if it is not
                                                        // empty

            if (line.equals("quit")) { // When the user is finished this exits
                                    // the program
                break;
            } else {
                football_list[counter] = line; // The below String is printed
                                            // for the amount of values
                                            // inside the counter integer

                System.out.println("Home team : Away team : Home score : Away score");
            }

            counter++; // counter is incremented
        }

        for (int i = 0; i < counter; i++) { // A loop to control the Array
            String[] words = football_list[i].split(":"); // Splits the input
                                                        // into 4 strings
            if (words.length != 4) {
                System.out.println("Input was not valid.");
            } else
                System.out.println(words[0].trim() + " [" + words[2].trim() + "]" + " | " + words[1].trim() + " ["
                    + words[3].trim() + "]"); // Formats and prints the output

        }

    }
}

考虑使用验证器方法，因为有很多验证要做。

它看起来像这样：

public static boolean validateString(String input) {
    if (input.split(":").length != 4) {
        return false;
    }
    for (String info : input.split(":")) {
        if (info.length() == 0) {
            return false;
        }
    }
    return true;
}

你的for-loop逻辑可能是

for (int i = 0; i < counter; i++) { // A loop to control the Array
        String[] words = football_list[i].split(":"); // Splits the input
                                                        // into 4 strings
        if (Main.validateString(football_list[i])) {
            System.out.println(words[0].trim() + " [" + words[2].trim() + "]" + " | " + words[1].trim() + " ["
                    + words[3].trim() + "]"); // Formats and prints the output
        }
        else{
            System.out.println("Your input of " + football_list[i] + " was not valid.");
        }
    }

另外，请考虑使用ArrayList而不是数组。您不必保留counter或将最大输入数设置为100.

Answer 2

如果您执行此类操作以检查数组是空还是空，该怎么办：

if(words[0] != null && words[0].length() > 0) {
   //it is not null and it is not empty
}else{
   //you can have the error message here
   System.out.println("It's null or empty");
}

如何验证字符串数组中的用户输入？

2 个答案: