How do I get a string user input and increase value by +1 using Java ArrayList?

Question

I have the following code and I want to ask the user after an name that's already stored in the Arraylist and increase that (dogs) age by +1.

Here's the most important (I guess) part of the code. This is the Register Class.

import java.util.Scanner;
import java.util.ArrayList;

public class Register {

private Scanner keyboard = new Scanner(System.in); 
private ArrayList<Dog> dogs = new ArrayList<>();


private String readString() {
    return keyboard.nextLine();
}

public int readInt() {
    int i = keyboard.nextInt();
    keyboard.nextLine();
    return i;
}

public double readDouble() {
    double d = keyboard.nextDouble();
    keyboard.nextLine();
    return d;
}


public void registrateDog(){ 

    System.out.println("Dogs name: ");
    String name = readString();

    System.out.println("Dogs breed: ");
    String breed = readString();

    System.out.println("Dogs age: ");
    int age = readInt();

    System.out.println("Dogs weight: ");
    double weight = readDouble();

    Dog newDog = new Dog(name, breed, age, weight);
    dogs.add(newDog);

    System.out.println(newDog.toString() + " is added");

  }



public void increaseAge(){ //Here's the problem

    System.out.print("Enter dog who has aged: ");
    String newDogAge = readString();

    int addAge = 1;

    for (int i = 0; i < dogs.size(); i++) { 
        if(dogs.get(i).getName().equals(newDogAge))

        addAge = (dogs.get(i).getAge());
        dogs.set(i, dogs.get(i));


        System.out.println("Dog " + newDogAge + " is now " + addAge);
        return;

    }
    }

private void exitProgram(){
    System.out.println("Goodbye!");
    keyboard.close();


}

private void run(){
    setUp();
    runCommandLoop();
    exitProgram();

}

public static void main(String[] args){

    new Register().run();
    //setUp();
}


}

And

public class Dog {

private String name;
private String breed;
private int age;
private double weight;
private double tailLenght;
private String tax = "tax";

public Dog(String name, String breed, int age, double weight){
this.name = name;
this.breed = breed; 
this.age = age;
this.weight = weight;
if (breed.equals(tax)) {
    this.tailLenght = 3.7;
} else {
    this.tailLenght = (age*weight) / 10;
}
}



public String getName(){
    return name;
}

public void setName(String name) {
this.name = name;
}

public String getBreed(){
    return breed;
}

public int getAge(){
    return age;
}

public void setAge(int age){
    this.age = age;
}

public int newAge(){
    return age = age + 1;
}



public double getWeight(){
    return weight;
}

public double getTailLenght(){
return tailLenght;
}

public String toString()
   { return String.format("%s, %s, %d years old, %.1f kg, "
    + "tail lenght %.1f cm", name, breed, age, weight, tailLenght);  
   }
}

Answer 1

So in this code you're finding the Dog by its name. Which is great.

public void increaseAge() {
    System.out.print("Enter dog who has aged: ");
    String newDogAge = readString();
    int addAge = 1;

    for (int i = 0; i < dogs.size(); i++) { 
        if(dogs.get(i).getName().equals(newDogAge))
            addAge = (dogs.get(i).getAge());
        dogs.set(i, dogs.get(i));
        System.out.println("Dog " + newDogAge + " is now " + addAge);
        return;
    }
}

Inside of your Dog class you have a method which returns the age, what you want to do is modify it to:

public int newAge(){
    this.age++; // This will take the current age of the dog and add one to it
}

Now going back to the increaseAge() method you want to modify the for loop to look like:

for (int i = 0; i < dogs.size(); i++) { 
    if(dogs.get(i).getName().equals(newDogAge))
        dogs.get(i).newAge(); // This will update the Dogs age by 1 year
        System.out.println("Dog " + dogs.get(i).getName() + " is now " + dogs.get(i).getAge());
        return;
}

Answer 2

Where are you incrementing the age ? Call the newAge() method as you have defined in the Dog class.`

     Dog dog = dogs.get(i);
     dog.setAge(dog.newAge());
     dogs.set(i,dog);`

We've fetched the particular dog who's details matched. Then we incremented it's age and set it back in the list at that position.