CODEWITHSUNDEEP
javaswitch-statement
maclunian
maclunian

Reputation: 8023

Java Switch Statement to manipulate Enum case

I have the following segment of a java file:

Integer x; Integer y; Face facing;

enum Rotate { Clockwise, Anticlockwise };

enum Face { East, North, West, South };

and am having trouble figuring out how to implement a function to change the Face of an object (i.e. the direction that the object is facing).

The function begins as follows

private void rotateIt(Rotate rotateIt) {
    {

I have begun using the switch statement as follows ( below text is inside braces above ):

switch (facing)
case North  : ...?;
case West   : ...?;
case East   : ...?;
case South  : ...?;

I'd like to use the Clockwise enumeration to turn it from East to South etc. and Anticlockwise to do the reverse IYGWIM.

Upvotes: 0

Views: 1173

Answers (5)

Blindy
Blindy

Reputation: 67380

switch (facing) {
  case North  : facing=rotateIt==Rotate.Clockwise?Face.East:Face.West; break;
  case West   : facing=rotateIt==Rotate.Clockwise?Face.North:Face.South; break;
  case East   : facing=rotateIt==Rotate.Clockwise?Face.South:Face.North; break;
  case South  : facing=rotateIt==Rotate.Clockwise?Face.West:Face.East; break;
}

I should get a large percent of your grade retroactively!

Upvotes: 4

Peter Lawrey
Peter Lawrey

Reputation: 533492

Another option is to use the enum to do the work.

enum Face { 
    North, East, South, West; // must be clockwise order.
}

enum Rotate { 
    private static final Face[] FACES = Face.values();
    Clockwise {
        public Face rotate(Face face) {
            return FACES[(ordinal()+1)%FACES.length];
        }
    }, 
    Anticlockwise {
        public Face rotate(Face face) {
            return FACES[(ordinal()+FACES.length-1)%FACES.length];
        }
    }
    public abstract Face rotate(Face face);
};

facing = rotateIt.rotate(facing);

Upvotes: 1

maasg
maasg

Reputation: 37435

I would implement rotate as a function of the Face orientation:

 enum RotationDirection { Clockwise, CounterClockwise };
 enum Face {
    East, North, West, South ;

    Face rotate(RotationDirection direction ) {
        int tick  = (direction == RotationDirection.Clockwise)?-1:1;
        int index = this.ordinal()+tick ;
        int length = Face.values().length-1;
        if (index <0) index = length;
        if (index >length) index = 0;
        return Face.values()[index];
    }

Then you can do things like:

 Face face = Face.North;
 face.rotate(RotationDirection.Clockwise); // East
 face.rotate(RotationDirection.CounterClockwise); //West

This code makes use of the seldom used 'ordinal' property of Enums. It therefore requires that the values are in a logical turning order e.g. (east, north, west, south)

Upvotes: 2

J&#233;r&#244;me Verstrynge
J&#233;r&#244;me Verstrynge

Reputation: 59576

You are starting fine. Here is a more complete version of what you have to do regarding enum manipulation:

public void RotateIt(Rotate toRotate, Face facing) {

switch (facing) {
    case North:
        // Include code to rotate from north
        break;
    case West:
        // Include code to rotate from west
        break;
    case East:
        // Include code to rotate from east
        break;
    default: // South
        // Include code to rotate from south
        break;
}

}

Of course, this code could be optimized, but it gives you an idea of how to handle enums in switch statements.

Upvotes: 0

Grammin
Grammin

Reputation: 12205

case North:
{
  if(rotateIt == Rotate.Clockwise)
    facing = Face.EAST
  else
    facing = Face.WEST
  break;
}

and so on...

Upvotes: 0

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