JAVA Loop with a defined sequence of numbers

Question

I'm currently programming an autonomous robot in java and here is my problem;

I want to know the orientation of my robot at all time, considering there is only 4 possible orientations:

Up / Down / Left / Right

I define each of these positions with the following numbers:

Up and Down = 0 , Left = 1 , Right = -1

So say my robot is currently oriented "0" (say up), and I turn 90 degrees on the right then the value should change to 1. If I rotate 90 degrees on the right again it will change back to 0.

So we have the following sequence: 0 , -1 , 0 , 1 (we can start at any point).

Basically my robot will encounter different types of obstacles. Everytime he meets one he will either turn right or left. I want him to always try to turn in the "up" direction. if the robot turns while being on a "0" position it doesn't matter because it doesn't affect the Y position (if we consider a X-Y axis). But if he is on a 1 or -1 position then he will have to turn 90° * 1 or 90° * (-1).

I'm struggling with finding how to change properly my CURRENT value depending on how many "quadrants" on the right (or left) the robot is rotating. I thought of exponents of (-1) but I couldn't figure out how.

Can you please help me with that?

Thank you!

P.S. I know I could just check the value with if conditions but there are lots of different classes and I use many times the method to rotate, so it needs to be as short and simple as possible.

Like @Gurwinder I would suggest using "N,S,E,W" instead of range -1 to 1. — Alvin Bunk
– Alvin Bunk, Commented Nov 29, 2016 at 17:34
It is because of how the whole thing works and basically these values will be used as multipliers for other methods. @Gurwinder — Fred vh
– Fred vh, Commented Nov 29, 2016 at 17:34
Please provide some example code in the question how you're using it and where exactly you face the issue. — Gurwinder Singh
– Gurwinder Singh, Commented Nov 29, 2016 at 17:38

JFPicard · Accepted Answer · 2016-11-29 17:58:27Z

2

Your problem seems a good candidate to experiment with sinus or cosinus functions.

If you use your problem as a quadrant, you can use the proprieties of the sinus like:

sin(0) = 0 
sin(90) = 1 
sin(180) = 0 
sin(270) = -1

In that case, the 0 and 180 degrees are 0 (N and S) and E - W are 1 and -1 respectively.

Can that help you ?

answered Nov 29, 2016 at 17:58

JFPicard

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2 Comments

Fred vh Over a year ago

Thanks I'm going to try it out!

timgeb Over a year ago

@FredV if an answer worked for you, remember that you can accept it to say thanks!

user180100 · Accepted Answer · 2016-11-29 17:58:51Z

You could use some enum to do what you need:

enum Orientation {
    NORTH, EAST, SOUTH, WEST;

    // clockwise
    public Orientation turnRight() {
        Orientation[] values = values();
        int ordinal = this.ordinal();
        if (ordinal == values.length - 1) {
            return NORTH;
        }
        return values[ordinal+ 1];
    }

    // counter-clockwise
    public Orientation turnLeft() {
        Orientation[] values = values();
        int ordinal = this.ordinal();
        if (ordinal == 1) {
            return WEST;
        }
        return values[ordinal - 1];
    }
}

(Live demo).

If you need the numeric values, just add a field (and a constructor) to the enum:

enum Orientation {
    NORTH(0), EAST(1), SOUTH(0), WEST(-1);

    private final int foo;

    private Orientation(final int foo) {
        this.foo = foo;
    }

    // getter for "foo"

then Orientation.NORTH.turnLeft().turnLeft().turnLeft().getFoo();

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