Java 班级获胜'；无法识别用户输入？

程序将无法识别我为gerbil.foodTypes输入的值（为gerbil.foodName.length输入的值为0。为什么

class Gerbil {
public int foodTypes;
public String[] foodName = new String[foodTypes];
}
public class mainmethod {
public static void main(String args[]) {
    Scanner keyboard = new Scanner(System.in);
    Gerbil gerbil = new Gerbil();
    System.out.println("How many types of food do the gerbils eat?");
    gerbil.foodTypes = keyboard.nextInt();
    for (int x = 0; x < gerbil.foodTypes ; x++) { 
        System.out.println("Enter the name of food item " + (x+1));
        gerbil.foodName[x] = keyboard.nextLine();
        keyboard.nextLine();
        System.out.println("Maximum consumed per gerbil:");
        gerbil.foodMax[x] = keyboard.nextInt();
    }

类沙鼠{
公共int食物类型；
公共字符串[]foodName=新字符串[foodTypes]；
}
公共类方法{
公共静态void main（字符串参数[]）{
扫描仪键盘=新扫描仪（System.in）；
沙鼠沙鼠=新沙鼠（）；
沙鼠吃多少种食物；
gerbil.foodTypes=keyboard.nextInt（）；
对于（int x=0；x

当计算新字符串[foodTypes]时，

foodTypes

为0，因此

foodName

始终为零长度数组

可能会添加一个采用

foodTypes

的构造函数

Gerbil gerbil = new Gerbil(keyboard.nextInt());

---

构造类时，数组“foodName”以零长度启动。原因是当您声明一个整数时，例如

public int foodTypes'

，编译器看到的是

public int foodTypes=0；

数组初始化后无法调整大小，因此无法“重置”数组的大小

我将添加一个构造函数，该构造函数从输入中获取一个数字并将其分配给foodTypes，因此它不是0

以下是一些未经测试的代码：

class Gerbil {
public int foodTypes;
public String[] foodName;

public Gerbil(int num){
    this.foodTypes = num;
    this.foodName = new String[foodTypes];
}
}
public class Assignment4 {
public static void main(String args[]) {
    Scanner keyboard = new Scanner(System.in);
    System.out.println("How many types of food do the gerbils eat?");
        Gerbil gerbil = new Gerbil(keyboard.nextInt());
    for (int x = 0; x < gerbil.foodTypes ; x++) { 
        System.out.println("Enter the name of food item " + (x+1));
        gerbil.foodName[x] = keyboard.nextLine();
        keyboard.nextLine();
        System.out.println("Maximum consumed per gerbil:");
        gerbil.foodMax[x] = keyboard.nextInt();
    }

类沙鼠{
公共int食物类型；
公共字符串[]foodName；
公共沙鼠（国际数量）{
this.foodTypes=num；
this.foodName=新字符串[foodTypes]；
}
}
公共课堂作业4{
公共静态void main（字符串参数[]）{
扫描仪键盘=新扫描仪（System.in）；
沙鼠吃多少种食物；
沙鼠沙鼠=新沙鼠（keyboard.nextInt（））；
对于（int x=0；x

---

是关于数组的进一步文档。

构造函数是做什么的？我尝试了你所说的，但没有成功。

class Gerbil {
public int foodTypes;
public String[] foodName;

public Gerbil(int num){
    this.foodTypes = num;
    this.foodName = new String[foodTypes];
}
}
public class Assignment4 {
public static void main(String args[]) {
    Scanner keyboard = new Scanner(System.in);
    System.out.println("How many types of food do the gerbils eat?");
        Gerbil gerbil = new Gerbil(keyboard.nextInt());
    for (int x = 0; x < gerbil.foodTypes ; x++) { 
        System.out.println("Enter the name of food item " + (x+1));
        gerbil.foodName[x] = keyboard.nextLine();
        keyboard.nextLine();
        System.out.println("Maximum consumed per gerbil:");
        gerbil.foodMax[x] = keyboard.nextInt();
    }