How to use If statements with Boolean and to read user input

Question

I did a post yesterday about this problem but was completely wrong with how i wrote so ive spent the night and this morning trying again and still cant get my head around how to do it.

What i'm trying to do is test my IsInRoom method by getting the user to input two coordinates i cant figure out how to get the user input read by the IF statement and everytime is use r.IsInRoom it comes up with an error saying "the method IsInRoom(Point) in the type room is not applicable for the arguments double.

I have tried so many different ways of doing this and everytime i keep ending up back in the same place. if any one has any ideas that would be great im really new to java so would be great if you could give me some pointers on how to use these functions properly?

Ive made the changes to the If else statement but in getting this error

   Exception in thread "main" java.lang.NullPointerException
    at CurtisBaldwin.buildingconsole.Room.isInRoom(Room.java:85)
   at aCurtisBaldwin.buildingconsole.Room.main(Room.java:115)

i think this is because ive not assigned the user input to the if statement? but im not sure how you do that

import java.awt.Point;
import java.io.Reader;
import javax.swing.JOptionPane;
import java.util.Random;

public class Room {
    private static int X; 
    private static int Y; 
    private static Point P; 
    private int[] coords;
    Random ranGen;

    public Room(String rstr) {
        StringSplitter S = new StringSplitter(rstr, " ");
        coords = S.getIntegers();
    }

    public Point getRandomPoint (Random ranGen) {
        return new Point(coords[0] +1 + ranGen.nextInt(coords[2] - coords[0] -2), (coords[1] +1 + ranGen.nextInt(coords[3] - coords[1] -2)));                                               
    }

    public String toString() {
        return "Room " + coords[0] + ", " + coords[1] + ", " + coords[2] + ", " + coords[3] + " Door " + coords[4] + ", " + coords[5];
    }

    public boolean IsInRoom(Point xy) {
        P = new Point (X,Y);

        return (xy.getX() > coords[0] && xy.getX() < coords[2] && xy.getY() > coords[1] && xy.getY() < coords[3]);
    }

    public static void main(String[] args) {
        Room r = new Room("0 0 5 5 0 2"); // create room
        System.out.println(r.toString()); // and print it

        String userIn = JOptionPane.showInputDialog
            (null, "please enter two coordinates one X and one Y separated by a space");
        JOptionPane.showMessageDialog(null, r.IsInRoom(P) + userIn);

        if (r.IsInRoom(P.getX() ) ) {
            System.out.println( (int) P.getX() + "," + (int) P.getY() + "Is in room");
        }
        else if (r.IsInRoom(P.getY() ) ){
            System.out.println((int) P.getX() + "," + (int) P.getY() + "Is in room");
        else (r.IsInRoom(P.getXY() ) ) { 
            System.out.println ((int) P.getX() + "," + (int) P.getY() + "Is not in room");
        }
    }
 }

While the error is pretty obvious, there's a big problem with how you designed the class. For example the fact that you keep state inside class members but still send it around in methods. — Federico klez Culloca
– Federico klez Culloca, Commented Nov 5, 2018 at 10:40

Kevin Cruijssen · Accepted Answer · 2018-11-05 10:39:37Z

1

The error states what's wrong. Your isInRoom method expects a Point parameter, but in your if(r.isInRoom(P.getX())) or if(r.isInRoom(P.getY())) the getX() and getY() are double types, which is why your get the error..

Simply changing your if-else construction to this:

if(r.isInRoom(P)){
  System.out.println((int)P.getX() + "," + (int)P.getY() + "Is in room");
} else{
  System.out.println((int)P.getX() + "," + (int)P.getY() + "Is not in room");
}

Is enough to fix it.

PS: Methods and variables are usually in camelCase, so IsInRoom should be isInRoom. It's not a requirement, but it's best practice for Java programming.

answered Nov 5, 2018 at 10:39

Kevin Cruijssen

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2 Comments

Curtis B Over a year ago

hi thank you for your help with fixing my If else statement, how do i go about linking the user input as im currently getting an error Exception in thread "main" java.lang.NullPointerException on lines 113 and 85 which is the return statement on the isInRoom method and the joptionpane.showmessagedialog etc

Curtis B Over a year ago

i also went through and changed the name of IsInRoom to isInRoom

Federico klez Culloca · Accepted Answer · 2018-11-05 10:41:32Z

1

You did this mistake

P.getX() and P.getY() return double but in IsInRoom argument you are expecting Point :)

another point is that till java 11 we didn't support argument in else block like you did eg:

else (r.IsInRoom(P.getXY() ) )

edited Nov 5, 2018 at 10:41

Federico klez Culloca

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answered Nov 5, 2018 at 10:38

user4477122

1 Comment

Curtis B Over a year ago

Thanks for your help i appreciate it

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