How to pass a value back into a class in Java?

Kamel Mili 发表于 Dev

SputnicK

I am building an Interactive Fiction game that uses a second class to deal with commands. When I type a command it is sent to the second class to be processed. The problem is when I run the code my values (int x and int y) are not being passed back into the main class. How do I pass these values back into the main class so that northD will print?

Main class:

import java.util.Scanner;
import static java.lang.System.out;

    public class Main {

        static String cmdIF;
        static int x = 0;
        static int y = 0;
        static String northD;
        public static void main(String[] args) {

            Scanner input = new Scanner(System.in);

            out.println("Welcome to the world! Which way do you want to go?");
            cmdIF = input.nextLine();
            choosePath();
            if(x==1 || y == 0) {
             northD = "You have entered the woods.";
                out.print(northD);
            }
        }
        public static void choosePath() {
            actionClass.cmdCenter(cmdIF, x, y);
        }
    }

Second class:

import static java.lang.System.out;
public class actionClass {
 public static void cmdCenter(String cmdIF, int x, int y) {
     if(cmdIF.equalsIgnoreCase("NORTH") || cmdIF.equalsIgnoreCase("GO NORTH")){ 
      x++;
     }
     else if(cmdIF.equalsIgnoreCase("EAST") || cmdIF.equalsIgnoreCase("GO EAST")) {
      y++; 
      }
     else if(cmdIF.equalsIgnoreCase("SOUTH") || cmdIF.equalsIgnoreCase("GO SOUTH")) { 
      x--; 
      }
     else if(cmdIF.equalsIgnoreCase("WEST") || cmdIF.equalsIgnoreCase("GO WEST")) { 
      y--; 
      }
     else { out.println("You can't do that."); }
 }
}

Francesco Serra

You can return an array of integer (or better an object). This the simplest way (in my opinion)

Main class:

public class Main {

static String cmdIF;
static int x = 0;
static int y = 0;
static String northD;
public static void main(String[] args) {

    Scanner input = new Scanner(System.in);

    System.out.println("Welcome to the world! Which way do you want to go?");
    cmdIF = input.nextLine();
    choosePath();
    if(x==1 || y == 0) {
     northD = "You have entered the woods.";
        System.out.println(northD);
    } else {
        System.out.println("You have entered the home");
    }
}
public static void choosePath() {
    //Method return an array of integer
    int[] newPos = actionClass.cmdCenter(cmdIF, x, y);
    //GETX
    System.out.println(newPos[0]);
    //GETY
    System.out.println(newPos[1]);
    //set X
    x = newPos[0];
    //set Y
    y = newPos[1];
}
}

Activity class:

public class actionClass {
  public static int[] cmdCenter(String cmdIF, int x, int y) {
   if(cmdIF.equalsIgnoreCase("NORTH") || cmdIF.equalsIgnoreCase("GO NORTH")){ 
    x++;
 }
   else if(cmdIF.equalsIgnoreCase("EAST") || cmdIF.equalsIgnoreCase("GO EAST")) {
    y++; 
  }
   else if(cmdIF.equalsIgnoreCase("SOUTH") || cmdIF.equalsIgnoreCase("GO SOUTH")) { 
    x--; 
  }
   else if(cmdIF.equalsIgnoreCase("WEST") || cmdIF.equalsIgnoreCase("GO WEST")) { 
    y--; 
  }
   else { System.out.println("You can't do that."); }

 //New array, first position x, second position y
 int[] res = {x,y};
 //Return it
 return res;
}

}

Output:

Welcome to the world! Which way do you want to go?
EAST
0
1
You have entered the home

More output:

Welcome to the world! Which way do you want to go?
NORTH
1
0
You have entered the woods.

With an object

A more complex way is to use a custom object. So new class:

public class xyObj {

    public int x;
    public int y;

    //Set x and y
    public xyObj(int x,int y){
        this.x=x;
        this.y=y;
    }
    //get x
    public int getX(){
        return x;
    }
    //get y
    public int getY(){
        return y;
    }
}

Now activity class return this object:

public class actionClass {
 public static xyObj cmdCenter(String cmdIF, int x, int y) {
     if(cmdIF.equalsIgnoreCase("NORTH") || cmdIF.equalsIgnoreCase("GO NORTH")){ 
      x++;
     }
     else if(cmdIF.equalsIgnoreCase("EAST") || cmdIF.equalsIgnoreCase("GO EAST")) {
      y++; 
      }
     else if(cmdIF.equalsIgnoreCase("SOUTH") || cmdIF.equalsIgnoreCase("GO SOUTH")) { 
      x--; 
      }
     else if(cmdIF.equalsIgnoreCase("WEST") || cmdIF.equalsIgnoreCase("GO WEST")) { 
      y--; 
      }
     else { System.out.println("You can't do that."); }

     //new xyObj setting x and y
     xyObj ret = new xyObj(x, y);
     //return it
     return ret;
 }

}

We have to modify also the choosePath method

public static void choosePath() {
    xyObj xyPos = actionClass.cmdCenter(cmdIF, x, y);
    System.out.println(xyPos.getX());
    System.out.println(xyPos.getY());
    x = xyPos.getX();
    y = xyPos.getX();
}

Same output! Good luck!

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