如何将值设置为存储在 ArrayList 中的特定属性？

Question

I have a lot of objects stored inside of an ArrayList called allAnimals. Each object has 4 attributes for example Animal(02,"tiger",270.0,16) //ID,name,weight,age

I have the user choose from 5 different options with a switch statement. Four cases for each one and the fifth that lets the user change every single attribute.

Inside of each case I hade a Scanner to get his input(for example name) and after that I tried to use the allAnimals.set(i, name); //i for index

And I got an error. (incompatible types: java.lang.String cannot be converted to Animal)

I was thinking storing each attribute into variables exept the one that is going to change and then remove the animal from the list and then add it back with the new attribute.

For example if user wanted to change the name. Store ID,weight,age into variables allAnimals.remove(i) allAnimals.add(new Animal(02, user_input, 270.0, 16);

But I don't think that this is efficient.

I also thought of adding some Setter methods in the Animal class but I don't know how it will work.(or if it will work at all)

I'm new to this so sorry if I didn't explain something.

Here is some of my code:

System.out.println("Choose what you want to change from the menu below.");
System.out.println("--------------------------------------------------");
System.out.println("1. Change only its ID.");
System.out.println("2. Change only its name.");
System.out.println("3. Change only its weight.");
System.out.println("4. Change only its age.");
System.out.println("5. Change everything.");

Scanner get_new_option = new Scanner(System.in);
int option = get_new_option.nextInt();

switch(option)
{
   case 1:
   //Haven't tried to change the ID cause I have to test that the given ID doesn't already exist within the ArrayList

     System.out.println("Enter its ID.");
     Scanner get_new_id = new Scanner(System.in);
     int code = get_new_id.nextInt();
   break;

  case 2:
     System.out.println("Enter its name.");
     Scanner get_new_name = new Scanner(System.in);
     String name = get_new_name.nextLine();
     AllAnimals.set(i,name); //error here


  break;  
 //case 3:
 //break;
 }

Also here is a method that I use to initialise 15 animals that already shoudl exist in the zoo. I just call the method in my main.

static ArrayList<Animal> AllAnimals = new ArrayList<Animal>();
static void InitAnimals()
{
    AllAnimals.add(new Animal(1,"turtle",90,150));
    AllAnimals.add(new Animal(2,"dolphine",80,17));
    AllAnimals.add(new Animal(3,"crocodile",75,20));
    AllAnimals.add(new Animal(4,"cheetah",120,20));
    AllAnimals.add(new Animal (5,"tiger",200,20));
    AllAnimals.add(new Animal(6,"owl",40,20));
    AllAnimals.add(new Animal(7," bonobo",80,25));
    AllAnimals.add(new Animal(8,"brown bear",450,24));
    AllAnimals.add(new Animal(9,"anacoda",60,18));
    AllAnimals.add(new Animal(10,"bald eagle",63,30));
    AllAnimals.add(new Animal(12,"panda",200,24));
    AllAnimals.add(new Animal(13,"jaguar",260,21));
    AllAnimals.add(new Animal(14,"orangutan",430,26));
    AllAnimals.add(new Animal(15,"shark",300,26));
}

Answer 1

No need to rewrite objects, just get the object you need by id and change the fields in it directly or, for example, through setters

Answer 2

Given below is how you can change the name of the animal at index, i :

System.out.print("Enter new name: ");
String name = scanner.nextLine();
Animal animal = allAnimals.get(i);
animal.setName(name);
allAnimals.set(i, animal);

where scanner is an object of Scanner and setName is public setter method for the attribute, name .

Note: You should not create a new Scanner object for each input. Remove all Scanner instantiations and create just one instance eg Scanner scanner = new Scanner(System.in); at the beginning of the method where you have created the menu. Then, you can reuse scanner for all inputs inside the method.