Java:找不到符号

Question

在这个类中，我正在制作一个 catchFish 方法，它基本上从池塘中返回一条随机鱼，应该将鱼从池塘中删除并从方法中返回，如果没有鱼，则将返回 null

这是我的代码

import java.util.Random;

public class Pond {

  private int     MAX_FISH = 10;
  private Fish[]  fish = new Fish[MAX_FISH];
  private int     numFish;


  public Pond (int numFish, Fish[] fish) {
    this.numFish = numFish;
    this.fish = fish;
  }


  public int getNumFish() {
    return numFish;
  }


  boolean isFull(){
    if (numFish < MAX_FISH) {
      return false;
    } else {
      return true;
    }
  }

  public String toString(){
    return "Pond with " + numFish + " fish";
  }

  public void listFish() {
    System.out.println("Pond with " + numFish + " as follows:");
    for (int i = 0; i < numFish ; i++) {
      Fish f = fish[i];
      System.out.println("A " + f.getSize() + " cm " + f.getSpecies());
    }
  }

  public void add(Fish f) {
    if (isFull()) {
      System.out.println("Sorry, the pond is full!");
    } else {
      numFish++;
      fish[numFish-1] = f;
    }
  }

  public Fish catchAFish() {
    if (numFish == 0) {
      System.out.println("Sorry, the pond is empty!");
      return null;
    } else {
      Fish f = new Fish();
      int r = (int)Math.random()*(numFish-1);
      f = fish[r];
      if (r == (numFish -1)) {
        fish[r] = null;
      } else {
        fish[r] = fish[numFish-1];
      }
      numFish--;
      return f;
    }
  }
}

在 catchAFish 方法中，该行

Fish f = new Fish(); gives an error:

java:55: cannot find symbol

symbol : constructor Fish()

location: class Fish

我不明白我做错了什么？

编辑:

鱼类

public class Fish {

  private String      species;
  private int         size;


  public Fish(int size, String species) {
    this.size = size;
    this.species = species;
  }


   public String toString() {
          return " A " + size + " cm " + species;
    }

  public String getSpecies() {
    return species;
  }

  public int getSize() {
    return size;
  }


}

Answer 1

基本上...Fish 必须有一个非空构造函数，要求您在创建 Fish 实例时提供一个或多个参数。

查看 Fish 代码，您提供的唯一构造函数是...

 public Fish(int size, String species) {

没有“默认”构造函数(允许您使用new Fish())。

但我不相信您实际上需要创建一个新实例，因为您几乎立即重新分配它。

 Fish f = new Fish();
 int r = (int)Math.random()*(numFish-1);
 // Overridden...
 f = fish[r];

相反，您可以简单地使用...

 int r = (int)Math.random()*(numFish-1);
 Fish f = fish[r];