New to java: I'm not sure how to store the objects in the arrays after it is created. The program gets rid of it, making it null

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The main objective was to have a lake and add fish objects to it, which have details about their weight etc. But however, every time a new fish is created, the previous object appears as null instead of its location, which I could use my getName to get the name.

package com. company;

public class Main {

    public static void main(String[] args) {
        Lake l = new Lake("jersey", 1, 2, 3,4 );
        l.addFish("carp", 20, 1);
        l.addFish("josh",20,1);

        Lake n = new Lake("york",1,2,4,20);
        n.addFish("catfish",20,30);
        n.addFish("tot",20,30);
        n.addFish("salmon",20,30);
        n.addFish("shrimp",20,30);
        n.addFish("swordfish",20,30);


    }
}

package com. company;

import java.lang.reflect.Array;
import java.util.Arrays;

public class Lake {
    private String name;
    private double length;
    private double width;
    private double depth;
    private final int amountOfFish;
    private int currentFishAmount = 0 ;

    Lake(String name, double length, double width, double depth, int amountOfFish)
    {
        this.name = name;
        this.length = length;
        this.width = width;
        this.depth = depth;
        this.amountOfFish = amountOfFish;
    }

    public void addFish (String name, double length, double weight)
    {
        Fish fishInLake []  = new Fish[amountOfFish];
        fishInLake[currentFishAmount]= new Fish(name, length, weight);
        System.out.println("Lake: " + this.name +  "|" + "Fish:" + ""+ fishInLake[currentFishAmount].getName() + fishInLake[currentFishAmount].getLength());
        System.out.println(currentFishAmount);
        currentFishAmount++;
        System.out.println(Arrays.toString(fishInLake));
    }



}
package com.company;

import java.lang.reflect.Array;

public class Fish {
    private String name;
    private double length;
    private double weight;


    Fish (String name, double length, double weight){
        this.name = name;
        this.length = length;
        this.weight = weight;
    }

   public String getName(){
        return this.name;
   }

   public double getLength(){
        return this.length;
   }

   public double getWeight(){
        return this.weight;
   }

}

The main objective was to have a lake and add fish objects to it, which have details about their weight etc. But however, every time a new fish is created, the previous object appears as null instead of its location, which I could use my getName to get the name.

arrays java
2 Answers

First off, to make your output a bit more readable, add a toString() method in your Fish class:

 public String toString(){
    return this.name;
  }

Next, since you want the array to be saved every time a new fish is added to the lake, we want to make the array a private instance variable, and then initialize it in our constructor:

package com. company;

import java.lang.reflect.Array;
import java.util.Arrays;

public class Lake {
    private String name;
    private double length;
    private double width;
    private double depth;
    private final int amountOfFish;
    private int currentFishAmount = 0 ;
    private Fish[] fishInLake;

    Lake(String name, double length, double width, double depth, int amountOfFish)
    {
        this.name = name;
        this.length = length;
        this.width = width;
        this.depth = depth;
        this.amountOfFish = amountOfFish;
        this.fishInLake = new Fish[amountOfFish];
    }

    public void addFish (String name, double length, double weight)
    {
        fishInLake[currentFishAmount]= new Fish(name, length, weight);
        System.out.println("Lake: " + this.name +  "|" + "Fish:" + ""+ fishInLake[currentFishAmount].getName() + fishInLake[currentFishAmount].getLength());
        System.out.println(currentFishAmount);
        currentFishAmount++;
        System.out.println(Arrays.toString(fishInLake));
    }
}
user_146451010

better to create a static method or a static Array, otherwise every time that tries to insert data, the previous data will be disappearing, with a static Array the whole data will be there until program execution finish.

user_165571920
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