如何从if语句动态调用对象的引用名称？

Question

Please forgive my terminology and lack of understanding of Objects in Java. I'm making a console Monopoly game with some classes, Monopoly, Players, Property etc with Monopoly having my main in it. I've declared Property and Player objects in the Monopoly class. After a player has landed on a bought property I'm trying to dynamically call the owner of that property to add money into its .money variable of that player from the Property class.

I've tried making a method with if statement to return a Player object as well as just a method that would return a String version of the name of the owner of the property. My problem is I don't know how to use that to actually use as a reference to the player that owns it.

Property Class

public class Property {


    boolean available=false;
    Object owner;
    int rent = 0;
    int houses = 0;
    int hotels = 0;



}

Players Class

public class Players{
        Players(){
            int money=1500;
    }

        String name="";
        int money=0;
        int pos=0;
        int goCount=0;
        int diceDoubles=0;
        int rollsInJail=0;
        boolean outOfJailFreeCard=false;
        boolean jail=false;
        String player="";

        Scanner in=new Scanner(System.in);
        String getName(){
            name=(String) in.next();
            return name;
        }

    }

Position Class

public class Position {


public static Players playerFind(Object str, Players obj){
    if(str.equals(Monopoly.player1)){
        return Monopoly.player1;
    }
    else if(str.equals(Monopoly.player2)){
        return Monopoly.player2;
    }
    else if(str.equals(Monopoly.player3)){
        return Monopoly.player3;
    }
    else if(str.equals(Monopoly.player4)){
        return Monopoly.player4;
    }
    else if(str.equals(Monopoly.player5)){
        return Monopoly.player5;
    }
    else if(str.equals(Monopoly.player6)){
        return Monopoly.player6;
    }
    return obj;
}    

public static void place(int num, Players obj, Property prop)
    {
        Scanner in=new Scanner(System.in);



        if(num==1) {

            System.out.println(obj.name+" landed on Mediterranean Avenue.");
            if(Monopoly.mediterranean.available==true){
                System.out.println("Would you like to buy this property?(Yes or No)");
                String str = in.next();
                if(str.startsWith("y") || str.startsWith("Y")){
                    Monopoly.mediterranean.available=false;
                    Monopoly.mediterranean.owner=obj;
                    obj.money-=60;
                    System.out.println("You now own Meditarreanean Avenue!");
                    System.out.println("Your balance is "+obj.money);
                }
            }
            else{
                Players obj2 = playerFind(Monopoly.mediterranean.owner, obj);    
                System.out.println("Rent is due! "+Monopoly.mediterranean.owner+" owns this property. M2 has been subtracted from your account"
                       + " and added into "+Monopoly.mediterranean.owner+"'s bank roll.");
                Players.obj2.money+=2;
                System.out.println("Your balance is "+obj.money);

                }
        }
        else if(num==2) {
            System.out.println(obj.name+" landed on Community Chest.");


        }//etc...

Monopoly Class

public class Monopoly {
        static Players player1 = new Players();
        static Players player2 = new Players();
        static Players player3 = new Players();
        static Players player4 = new Players();
        static Players player5 = new Players();
        static Players player6 = new Players();
        //static Position position= new Position();
        static CommunityChest chest=new CommunityChest();
        static Property property=new Property();
        static Property mediterranean=new Property();
        static Property baltic=new Property();
        static Property reading=new Property();
        static Property oriental=new Property();
        static Property vermont=new Property();
        static Property connecticut=new Property();
        static Property stCharles=new Property();
        static Property states=new Property();
        static Property virginia=new Property();
        static Property pennRail=new Property();
        static Property stJames=new Property();
        static Property tennessee=new Property();
        static Property newYork=new Property();
        static Property kentucky=new Property();
        static Property indiana=new Property();
        static Property illinois=new Property();
        static Property bAndC=new Property();
        static Property atlantic=new Property();
        static Property ventor=new Property();
        static Property marvin=new Property();
        static Property pacific=new Property();
        static Property northCar=new Property();
        static Property pennAve=new Property();
        static Property shortLine=new Property();
        static Property parkPlace=new Property();
        static Property board=new Property();
        static Property electric=new Property();
        static Property water=new Property();

        static int playerNum=intro();

public static void play(int num, int rollCount){
        int roll1=0, roll2, i=0;


        while(i<rollCount-1){
            int i1=i+1;
            System.out.println("Beginning of turn "+i1);

            if(num>0){
                turn(player1);
                System.out.println(player1.name+" money count:M"+player1.money);
            }
            if(num>1){
                turn(player2);
                System.out.println(player2.name+" money count:M"+player2.money);
            }
            if(num>2){
                turn(player3);
            }
            if(num>3){
                turn(player4);
            }
            if(num>4){
                turn(player5);
            }
            if(num==6){
                turn(player6);
            }
            System.out.println("End of turn "+i1+"\n");
            i++;

        }
    }

    public static void turn(Players obj){
        Scanner in1=new Scanner(System.in);

        int roll1=roll();
        int roll2=roll();
        obj.pos=obj.pos + roll1 + roll2;
        System.out.println(obj.name+" rolled a "+roll1+" and a "+roll2);
        if(obj.jail==false){
            System.out.println(obj.name + " has landed on "+place(obj.pos));
        }

        if(roll1!=roll2){
            obj.diceDoubles=0;
        }

        Position.place(obj.pos, obj, property);

        if(obj.jail==true){//roll while in jail, check first in case they roll doubles and continue their turn. Turn must end after going to jail
            if(obj.outOfJailFreeCard==true){//if get out of jail card, prompt to use it rightaways
                    System.out.println("You've rolled thrice doubles in a row and have ended in up jail. Luckily you have a 'Get out of jail free' card!");
                    System.out.print("Would you like to use your 'Get out of jail free' card right now?: (Y/N)");
                    String check=in1.next();
                    if(check.startsWith("y") || check.startsWith("Y")){
                        obj.pos=10;
                        obj.outOfJailFreeCard=false;
                    }
                }
            if(roll1!=roll2){
                obj.rollsInJail+=1;
                if(obj.rollsInJail==3){
                    obj.pos=10+roll1+roll2;
                    obj.money-=50;
                    obj.rollsInJail=0;
                }return;//does this break out of method to end turn??
            }
            if(roll1==roll2){
                obj.pos=10+roll1+roll2;
                obj.rollsInJail=0;
            }return;//does this break out of method to end turn??
        }

        while(roll1==roll2 && obj.diceDoubles<3){//check for doubles
            obj.diceDoubles+=1;
            if(obj.diceDoubles==3){
                obj.jail=true;
                obj.diceDoubles=0;
                System.out.println("You've rolled doubles 3 times in a row. You are now in jail!");
                break;
            }
            else{turn(obj);
            break;}
        }

        if(obj.pos>39){//pass go, collect M200
            obj.pos=obj.pos - 39;
            obj.goCount=obj.goCount+1;
            obj.money+=200;
        }

        in1.close();// close scanner
    }

    public static void main(String[] args) {

        play(playerNum, 60);
    }

I'm trying to dynamically find the owner and make a reference to the actual object instance to add to its .money variable.

Answer 1

The problem is that you have owner as an Object reference, which doesn't have the money field. You need to use the Player class instead:

public class Property
{
 boolean available=false;
 Player owner;
 int rent = 0;
 int houses = 0;
 int hotels = 0;
}

And then you can directly move the rent between the two players, eg:

Property property = Monopoly.mediterranean;
activePlayer.money-= property.rent;
property.owner.money+= property.rent;

In a real game you would then add more checks, eg does the player have enough money to cover the rent or are there problems with parallelism that need to be covered, but that is the basic solution to your problem.