Java - 当数据超出限制时打印消息？

我的代码已经可以工作了，虽然不漂亮，但确实是工作:) 现在我想编写一段代码，如果文本文件中有 19 条或更多数据，则停止加载数据，然后显示例如，显示“输入无效”的消息。我不知道如何做到这一点，所以任何帮助将不胜感激。

package stackandqueue;

import java.util.*;
import java.util.Stack;
import java.util.Queue;
import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.util.LinkedList;
import java.util.StringTokenizer;
import java.util.Arrays;

public class StackAndQueue {

    public static void main(String[] args) throws IOException {
        // Create three empty stacks of Bays.
        // Bay 1 linked list
        Queue<String> bayoneStack = new LinkedList<String>();
        // Bay 2 linkd list.
        Queue<String> baytwoStack = new LinkedList<String>();
        // Bay 3 linked list
        Queue<String> baythreeStack = new LinkedList<String>();

        Queue<String> bayloadStack = new LinkedList<String>();

        System.out.println("***********************************************");

        // Open and read text file
        String inputFileName = "PodData4.txt";
        FileReader fileReader = new FileReader("PodData4.txt");

        // Create the FileReader object
        try (BufferedReader br = new BufferedReader(fileReader);) {
            // Sort the data into the relevant linked list by type F, T or P.
            String[] strings = br.readLine().split(",");
            for (String str : strings) {
                switch (str.charAt(0)) {
                case 'F':
                    bayoneStack.add(str);
                    break;
                case 'T':
                    baytwoStack.add(str);
                    break;
                case 'P':
                    baythreeStack.add(str);
                    break;
                default:
                    // In-case of invalid input

                }

                System.out.println(str);

            }
        } catch (IOException ex) {
            // handle exception;
        } finally {
            fileReader.close();
        }
        // Prints out the linked list stacks showing all Bays.
        System.out.println("***********************************************");

        System.out.println("Bay 1:Food: " + bayoneStack.toString());
        System.out.println("Bay 2:Technical: " + baytwoStack.toString());
        System.out.println("Bay 3:Personal: " + baythreeStack.toString());

    }
}

只需首先使用条件语句检查总长度即可。就像是

String test = br.readLine();
if (test.length() < 19) {
    String[] strings = test.split(",");
    //continue operations with string input
}
else {
    //change this to what you want the error to read.
    System.out.println("Invalid input.");
}

请注意，我改变了你的strings数组来分割test字符串而不是br.readLine()