Exception in thread error when running Interface

Question

I have written a code in which I have made an interface and a class that implements that interface. Now when I run the code, i give my self 2 options i.e. 1 to Enter string and 2 to quit. Now when i run the code, if i select 1, it lets me put in string, but after this when i press 0, it gives me error: Exception in thread "main" java.lang. Can some body please help me figure out what I am missing here. Below is the code:

import java.util.ArrayList;
import java.util.List;

public interface ITimsSaveable {

    List<String> write();  // this will save the data;
    void read (List<String> savedValues);  //this will print the data

}


import java.util.ArrayList;
import java.util.List;

public class TimsPlayers implements ITimsSaveable {
    private String name;
    private int hitPoints;
    private int strength;
    private String weapon;

    public TimsPlayers(String name, int hitPoints, int strength) {
        this.name = name;
        this.hitPoints = hitPoints;
        this.strength = strength;
        this.weapon = "Sword";
    }

    public String getName() {
        return name;
    }

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

    public int getHitPoints() {
        return hitPoints;
    }

    public void setHitPoints(int hitPoints) {
        this.hitPoints = hitPoints;
    }

    public int getStrength() {
        return strength;
    }

    public void setStrength(int strength) {
        this.strength = strength;
    }

    public String getWeapon() {
        return weapon;
    }

    public void setWeapon(String weapon) {
        this.weapon = weapon;
    }
    //now go to generate > to string method

    @Override
    public String toString() {
        return "TimsPlayers{" +
                "name='" + name + '\'' +
                ", hitPoints=" + hitPoints +
                ", strength=" + strength +
                ", weapon='" + weapon + '\'' +
                '}';
    }
    //now let us create stubs, i.e. the empty methods from interface

    @Override
    public List<String> write() {
        List<String > values = new ArrayList<String >();
        values.add(0,this.name);
        values.add(1,""+this.hitPoints); //"" is quick trick to convert int to String
        values.add(2,""+this.strength);
        values.add(3,this.weapon);
        return values;
    }

    @Override
    public void read(List<String> savedValues) {
        if ((savedValues != null) && (savedValues.size() > 0)) {
           this.name = savedValues.get(0);
           this.hitPoints = Integer.parseInt(savedValues.get(1));
           this.strength = Integer.parseInt(savedValues.get(2));
           this.weapon = savedValues.get(3);
        }
        // now let us go back to our main class
    }
}


public class Main {

    public static void main(String[] args) {

    TimsPlayers tim = new TimsPlayers("Tim",10,15);
        System.out.println(tim.toString());
        saveObject(tim);

        tim.setHitPoints(8);
        System.out.println(tim);
        tim.setWeapon("Stormbringer");
        saveObject(tim);
        loadObject(tim);
        System.out.println(tim);

    }
    public static ArrayList<String> readValues() {
        ArrayList<String> values = new ArrayList<String>();

        Scanner scanner = new Scanner(System.in);
        boolean quit = false;
        int index = 0;
        System.out.println("Choose\n" +
                "1 to enter a string\n" +
                "0 to quit");

        while (!quit) {
            System.out.print("Choose an option: ");
            int choice = scanner.nextInt();
            scanner.nextLine();
            switch (choice) {
                case 0:
                    quit = true;
                    break;
                case 1:
                    System.out.print("Enter a string: ");
                    String stringInput = scanner.nextLine();
                    values.add(index, stringInput);
                    index++;
                    break;
            }
        }
        return values;
    }

    public static void saveObject(ITimsSaveable objectToSave) { //ITims is the interface that is being implemented by the player
    

//class,so we can use ITims as object type
    for (int i = 0; i < objectToSave.write().size(); i++) {
        System.out.println("Saving " + objectToSave.write().get(i) + " to storage device");
    }
    }
        public static void loadObject (ITimsSaveable objectToLoad) {
            ArrayList<String > values = readValues();
            objectToLoad.read(values);
    
    }
    }

Stacktrace:

Exception in thread "main" java.lang.IndexOutOfBoundsException: Index 1 out of bounds for length 1 at java.base/jdk.internal.util.Preconditions.outOfBounds(Preconditions.java:64) at java.base/jdk.internal.util.Preconditions.outOfBoundsCheckIndex(Preconditions.java:70) at java.base/jdk.internal.util.Preconditions.checkIndex(Preconditions.java:248) at java.base/java.util.Objects.checkIndex(Objects.java:373) at java.base/java.util.ArrayList.get(ArrayList.java:427) at org.mm.sandbox.so.TimsPlayers.read(TimsPlayers.java:77) at org.mm.sandbox.so.Main.loadObject(Main.java:62) at org.mm.sandbox.so.Main.main(Main.java:17)

Answer 1

This method

@Override
public void read(List<String> savedValues) {
    if ((savedValues != null) && (savedValues.size() > 0)) {
        this.name = savedValues.get(0);
        this.hitPoints = Integer.parseInt(savedValues.get(1));
        this.strength = Integer.parseInt(savedValues.get(2));
        this.weapon = savedValues.get(3);
    }
    // now let us go back to our main class
}

expects the savedValues to be completely filled, i.e. having 4 elements - name, HP, strength and weapon. You do savedValues.size() > 0 but that doesn't mean you didn't just input one of the required and then stopped and it still tries to access an element which does not exist - this.hitPoints = Integer.parseInt(savedValues.get(1));