在Java中打印来自2d数组的值

Question

我正在开发一个程序，允许用户将值添加到2d数组，然后搜索数组并显示值。 信息已正确存储，但是我只能显示动物名称而不是食物。 在被烤之前，我已经搜索并实现了许多不同的方法来尝试获得正确的输出。 我敢肯定，如果有人可以帮助我理解我的错误，那就非常简单了，谢谢！

/*This program will allow a user to enter information into the zoo
or search by animal for the type of food it eats*/

import java.util.Scanner;

class zoo {
    //create array
    static String[][] animalFood;

    String[][] addArray(int x) {

    animalFood = new String[x][2];
    Scanner in = new Scanner(System.in);

   //loop through array and add amount of items user chose
    for (int row = 0; row < animalFood.length; row++){
        System.out.print("Enter an animal name: ");
        animalFood[row][0] = in.nextLine();
        System.out.print("Enter the food the animal eats: ");
        animalFood[row][1] = in.nextLine();
        }

        System.out.println("Thank you for adding information to the zoo!");
        System.out.println("You entered the following information: ");

        //loop through and print the informationa added
        for(int i = 0; i < animalFood.length; i++)
        {
           for(int j = 0; j < animalFood[i].length; j++)
           {
            System.out.print(animalFood[i][j]);
            if(j < animalFood[i].length - 1) System.out.print(" - ");
             }
            System.out.println();
}
       //prompt the user to search or quit
       System.out.println("Please enter the name of the animal to search for or Q to quit: ");
          String animalName = in.nextLine();
        animalName = animalName.toUpperCase();
        if(animalName.equals("Q")){
         System.out.println("Thanks for using the program!");
        }
        else {
           searchArray(animalName);
        }

         return animalFood;

}

String[][] searchArray(String name) {

   String matchResult = "There was no " + name + " found in the zoo!"; 
   String itemToMatch = name.toUpperCase();
   String arrayItem = "";
   String food = "";
   for (int i = 0; i < animalFood.length; i++) {
      for (int j = 0; j < animalFood.length; j++) {
         arrayItem = animalFood[i][j];
         arrayItem = arrayItem.toUpperCase();
         if(arrayItem.equals(itemToMatch)){ 
            matchResult = "The animal " + name + " was found in the zoo! It eats " + animalFood[j];        
         }
         else {
            //nothing found
         }      

      }
    }
    System.out.println(matchResult);
    if (food != null) {
    System.out.println(food);
    }
    return animalFood;
}

//constructor
public zoo() {

}

//overloaded constructor
public zoo(int x) {

   int number = x;
   animalFood = addArray(x);
}

//method to get users choice
public static int menu() {

    int selection;
    Scanner input = new Scanner(System.in);

    System.out.println("Please make a choice in the menu below");
    System.out.println("-------------------------\n");
    System.out.println("1 - Add animals and the food they eat.");
    System.out.println("2 - Search for an animal in the zoo.");
    System.out.println("3 - Exit the program");

    selection = input.nextInt();
    return selection;    
}

//main method
public static void main(String[] args) {

    //create a new object
    zoo myZoo = new zoo();

    //variables and scanner
    int userChoice;
    int numberAnimals;
    String animalName = "";
    Scanner input = new Scanner(System.in);

    //call the menu
    userChoice = menu();

    //actions based on user choice
    if (userChoice == 1) {
        System.out.println("How many animals would you like to enter information for?");
        numberAnimals = input.nextInt();
        myZoo.addArray(numberAnimals);
    }

    if (userChoice == 2) {
        System.out.println("Please enter the name of the animal to search for: ");
        animalName = input.nextLine();
        myZoo.searchArray(animalName);
    }

    if (userChoice == 3) {
        System.out.println("Thank you for using the program!");
    }
}
}

Answer 1

在我看来，你的问题在于searchArray 。 您的嵌套for循环迭代超过数组的一个维度的大小：

for (int i = 0; i < animalFood.length; i++) {
  for (int j = 0; j < animalFood.length; j++) {
    ...
  }
}

用animalFood[i].length替换animalFood.length ，就像你在addArray方法中正确使用addArray 。

编辑

它看起来也像你的输出方法不正确。

matchResult = "The animal " + name + " was found in the zoo! It eats " + animalFood[j];

在这一行中， animalFood[j]应该是animalFood[i][j] 。 您看到的奇怪输出是Java尝试将数组转换为String。

第二次编辑

在检查了addArray方法之后，似乎我对你的数组做了一个不正确的假设。 看起来您的数组的结构使得每个索引都有2个项目，即动物及其食物。 所以它看起来像这样：

animalFood [0] [0] ='猫'
animalFood [0] [1] ='猫食'
animalFood [1] [0] ='狗'
animalFood [1] [1] ='狗粮'
等等

如果是这种情况，那么您将需要更改循环以仅对外部索引进行迭代。 这意味着删除searchArray内部的for循环。 然后，你只是将内部数组的第一个索引与你想要匹配的项目进行比较，如果匹配，那么食物将是第二个索引。 我会把实现留给你（因为这看起来像是一个家庭作业问题）。 如果我在这里说的话听起来不对，请告诉我。