Mars Rover Project

Question

When getting the input in the main() function.... the input for the String object instSet' gets skipped.... can someone explain why this happens and how to rectify...for now i am only enclosing my public class. if required ill add the other classes later...

import java.util.Scanner;

public class MarsRover {

    private String inst_set;
    private Plateau p;
    private Cell currentLocation;

    public enum Direction{N,S,E,W}

    Direction dir;

    public MarsRover(Plateau p1, int x, int y, Direction dir, String instSet) {

        p=p1;
        inst_set=instSet;
        this.dir=dir;
        currentLocation=new Cell(x, y);


    }


    public void executeInst() {

        int i = 0;
        System.out.println(inst_set.length());
        while (i < inst_set.length()) {

            //System.out.println("Check");
            char inst = inst_set.charAt(i++); //get each inst seperately as a character

            if (inst=='M') {
                Cell temp=p.getNeighbour(dir, currentLocation);

                if (temp != null)
                     currentLocation=temp;

                else
                    continue;

            }

            if(inst=='L'||inst=='R'){

                dir=setDirection(dir,inst);

            }
        }



    }

    private Direction setDirection(Direction dir, char inst) {

        if(inst=='L') {
            switch (dir) {
                case N:
                    dir = Direction.W;
                    break;
                case W:
                    dir = Direction.S;
                    break;
                case S:
                    dir = Direction.E;
                    break;
                case E:
                    dir = Direction.N;
                    break;
            }

        }

        else if(inst=='R'){

            switch (dir) {
                case N:
                    dir = Direction.E;
                    break;
                case W:
                    dir = Direction.N;
                    break;
                case S:
                    dir = Direction.W;
                    break;
                case E:
                    dir = Direction.S;
                    break;
            }

        }

        return dir;

    }




    public static void main(String... a){

        Plateau p1=new Plateau();
        Scanner in = new Scanner(System.in);

        int x,y;
        String instSet;

        System.out.println("Enter the Initial XLocation:");
        x=in.nextInt();
        System.out.println("Enter the Initial YLocation:");
        y=in.nextInt();

        System.out.println("Enter the Instructions");
        instSet=in.nextLine();

        String dir;
        System.out.println("Enter the direction the rover is Headed");
        dir=in.nextLine();

        MarsRover mr1=new MarsRover(p1,x,y,Direction.valueOf(dir),instSet);
        mr1.executeInst();


    }

}

Can you tell us how did you observe it gets skipped? is there an error message? — milez, Jul 20 '15 at 11:08
@milez you would need to run the code and have a look by your own. — Rahul Winner, Jul 21 '15 at 03:36
There is no error message... i tries using instSet.length which returned 0. since it is 0. there are other parts of my code taht does not run. — leoOrion, Jul 22 '15 at 15:05

Rahul Winner · Accepted Answer · 2015-07-20T11:28:41.893

Simple Solution: you should simply call

instSet=in.next() + in.nextLine();

instead of

in.nextLine()

next() returns very first token from standard input. And nextLine() returns next line after this token.

Another solution: nextLine() after every nextInt(), like as below

    System.out.println("Enter the Initial XLocation:");
    x=in.nextInt();
    in.nextLine();
    System.out.println("Enter the Initial YLocation:");
    y=in.nextInt();
    in.nextLine();
    System.out.println("Enter the Instructions\t");
    instSet=in.nextLine();

If you use Scanner#next###() (except for nextLine), and you reach an end of line token as when the user presses enter, if you don't handle the end of line token, it will prevent the Scanner object from working appropriately. So, nextInt() is not reading the and that is being read by nextLine()

Hope it clarifies

@leoOrion would you like to accept the answer if it helps. Thanks. — Rahul Winner, Jul 21 '15 at 03:36

Mars Rover Project

1 Answers1