How to take a variable within a method of another class

Question

Good evening, I’m starting to learn Java and I came across this problem and I need help. I want to call a variable for my Main, only it is within a method. I’ve tried using player.Pawn(), but this only works if the method is returning something, and that’s not quite what I want.

Main:

public class Main {

public static void main(String[] args) {
    
    System.out.println("Bem vindo ao jogo!");
    System.out.println("Pressione qualquer tecla para começar");
    Scanner in = new Scanner(System.in);
    String start = in.nextLine();
    
    Player player = new Player();
    player.spawn();
    
    while(vivo)//variável que eu quero chamar
    {
        System.out.println("It just works");
    }
}

Player:

public class Player {

           public void spawn()
       {
           System.out.println("Jogador spawnado");
           boolean vivo = true;
           int vida = 3;
           int dano = 1;
           int defesa = 1;
           }

}

Answer 1

The correct way would be to create a getter method, to be able to access the live value, from within the Player class.

Follow an example:

Java player.

public class Player {
       private boolean vivo;
       public Player() {
             vivo = true;
       }
       public void spawn(){
           System.out.println("Jogador spawnado");
           int vida = 3;
           int dano = 1;
           int defesa = 1;
       }
       public boolean getVivo() {
          return vivo;
       }
}

Then in your class main.java, just call the method getVivo():

while(player.getVivo())//variável que eu quero chamar
{
    System.out.println("It just works");
}

Notice that in my solution we made the following steps:

1. put the live variable as an instance variable of the Player class.
2. We added a constructor method only to start the value of the live variable. (we could create (more than one constructor for example to have one that accepts parameters, to instill our class in a more adaptable way)
3. We added a getter for the value of the live variable.
4. In our main method we use the method getVivo()

Note that from this we are breaking some principles of object orientation programming using our class in this way, one of them is encapsulation.

If we do not want to break the encapsulation we must have a getter and a Setter for each attribute of our class. A more object-oriented version of our class would be:

Java player.

public class Player {
   private boolean vivo;
   private int vida;
   private int dano;
   private int defesa;

   public Player() {
   //construtor padrão
   }
   public Player(boolean vivo, int vida, int dano, int defesa) {
      this.vivo = vivo;
      this.vida = vida;
      this.dano = dano;
      this.defesa = defesa;
      System.out.println("Jogador spawnado");
   }
   
  public boolean getVivo() {
      return vivo;
  }
  public int getVida() {
      return vida;
  }
  public int getDano() {
      return dano;
  }
  public int getDefesa() {
      return defesa;
  }
  public void setVivo(boolean vivo){
      this.vivo = vivo;
  }
  public void setVida(int vida) {
      this.vida = vida;
  }
  public void setDano(int dano) {
       this.dano = dano;
  }
  public void setDefesa(int defesa) {
       this.defesa = defesa;
  }
}

Then in his main.java simply call the player class constructor with the values to instantiate its class.

Main java.

public class Main {

public static void main(String[] args) {
    
    System.out.println("Bem vindo ao jogo!");
    System.out.println("Pressione qualquer tecla para começar");
    Scanner in = new Scanner(System.in);
    String start = in.nextLine();
    
    //aqui usamos os valores que estavam dentro do método spawn()
    Player player = new Player(true, 3, 1, 1);
    //player.spawn(); -->não é mais necessário pois estamos utilizando o construtor
    
    while(player.getVivo())//variável que eu quero chamar
    {
        System.out.println("It just works");
    }
}