我有一個字符串，當輸入超出指定值時，該字符串被設置為默認值，但它不斷返回null而不是默認值。我缺少什么代碼才能獲得正確的輸出？我發現我的整數和雙精度值正確使用默認值，但我的字符串沒有。這是我的前端剪輯import java.util.Scanner;public class AnimalFrontEnd {    public static final int ARRAY_SIZE = 10;    Scanner keyboard = new Scanner(System.in) ;    public static void main(String[] args) {        boolean cont = true;        int input = 0;        int type = 0;        AnimalCollection collection = new AnimalCollection(ARRAY_SIZE);        Scanner keyboard = new Scanner(System.in) ;        String rName = "";        System.out.println("Welcome to the Cat and Dog Collection");        while(cont) {            System.out.println("1. Add a cat or dog \n2. Remove a cat or dog \n3. Quit \nEnter a selection");            input = Integer.parseInt(keyboard.nextLine());            switch(input) {            case 1:                System.out.println("Would you like to add \n1. A House Cat \n2. A Leopard \n3. A Domestic Dog \n4. A Wolf");                type = Integer.parseInt(keyboard.nextLine());                switch(type) {                case 1:                    HouseCat kitty = getHCat();                    collection.addAnimal(kitty);                    break;在我的前端進一步向下private static HouseCat getHCat() {        String name;        double weight;        String mood;        String cType;        Scanner keyboard = new Scanner(System.in) ;        System.out.println("Enter the cat's name, weight, mood, and type");        name = keyboard.nextLine();        weight = Double.parseDouble(keyboard.nextLine());        mood = keyboard.nextLine();        cType = keyboard.nextLine();        return new HouseCat(name, weight, mood, cType);    }