Java: setting a objects variable in outside function

Question

    public static void main(String[] args) {

        Player Anfallare = new Player("A");
        Player Forsvarare = new Player("F");
        MotVarandra(Anfallare.getDice(1), Forsvarare.getDice(1));
    (...)
   }

Is what I have in main function, now I made a own function,

public static void MotVarandra(int a, int f){
    if(f >= a){
        Anfallare.armees-=1;
    }else{
        Forsvarare.armees-=1;
    }
}

which should set the object's variable to -=1.. But this doesn't work because the function doesnt know that Anfallare and Forsvarare is an object..

What can i do in this case?

Community · Accepted Answer · 2017-05-23 12:04:19Z

5

You need to define the Players as class fields, instead of inside the main method.

For a gentle introduction to Java, I suggest you to start reading here:

http://download.oracle.com/javase/tutorial/java/index.html

Also, there are great book suggestions here: https://stackoverflow.com/questions/75102/best-java-book-you-have-read-so-far . Some of those books are great to begin learning.

Example here:

public class Game {
  private static Player Anfallare, Forsvarare; //  <-- you define them here, so they are available to any method in the class

  public static void main(String[] args) {

    Anfallare = new Player("A");  //  <-- it is already defined as a Player, so now you only need to instantiate it
    Forsvarare = new Player("F");
    MotVarandra(Anfallare.getDice(1), Forsvarare.getDice(1));
    // ...
  }
  public static void MotVarandra(int a, int f){
    if(f >= a){
        Anfallare.armees-=1; //  <-- it is already defined and instantiated
    }else{
        Forsvarare.armees-=1;
    }
  }
}

edited May 23, 2017 at 12:04

CommunityBot

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answered May 25, 2011 at 17:08

Aleadam

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5 Comments

Karem Over a year ago

Im learning Java in school and Im trying to make a own little project game but thanks for links although could you maybe specify another link more detail about how to define the players as class fields instead inside in main?

Aleadam Over a year ago

@Karem from the oracle link, follow "Language Basics" and "Classes and Objects". It will be much more helpful than just an example. Anyway, I added the example so you know what I'm talking about.

Aleadam Over a year ago

BTW, If you need to access the players form outside the class, you need to change private to public or create a set of "getters" and "setters" as Fredrik says.

Karem Over a year ago

thank you, learned something new today! I am receiving non-static method cannot be referenced from a static content on my public static void functions. I tried to change it to public void, but then my Motvandra() in the main are saying the same, because main is public static void. What do i do? Appreciate your patience..

Aleadam Over a year ago

@Karem I was not really thinking about the main method, do I forgot to add the static modifier to the variable. In a real program, you would create a hierarchy of objects and instantiate each player as instance fields instead of class fields. See the discussion about it here: download.oracle.com/javase/tutorial/java/javaOO/classvars.html

Cooper · Accepted Answer · 2011-05-25 17:36:43Z

While Aleadam's solution is by far the best answer, another thing you could do to specifically resolve this issue is change the arguments of the function:

public static void MotVarandra(Player a, Player f){
    if(f.getDice(1) >= a.getDice(1)){
        f.armees-=1;
    }else{
        a.armees-=1;
    }
}

Ultimately, your optimal solution just depends on what your program is doing. Chances are, this is just another way of looking at it.

As a side note, be sure to use descriptive naming techniques, a and f are somewhat hard coded, and only make sense if you use only those variable names for your Players. It's best to not potentially limit your code.

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