Unexpected ArrayIndexOutOfBoundsException
public static ArrayList<Grain> FindGrains(Point[][] p){
    ArrayList<Grain> grains = new ArrayList<Grain>();
    ArrayList<Point> growthPoints = new ArrayList<Point>();
    ArrayList<Point> previousPoints = new ArrayList<Point>();
    boolean finGrainGrow = false;
    int x = -1;
    int y = -1;
    int j, k;
    int grainNum =-1;
    double stepSize = 0.5;

    while(true){
        x = -1;
        y = -1;

        growthPoints.clear();
        previousPoints.clear();

        for(int f =0; f<p.length;f++){
            for(int r =0; r<p[0].length;r++){
                if(p[r][f].getGrainNum() == -1){
                    x = r;
                    y = f;
                    grains.add(new Grain());
                    grainNum++;
                    p[x][y].setGrainNum(grainNum);
                    grains.get(grainNum).add(p[x][y]);
                    growthPoints.add(0,p[x][y]);
                    break;
                }
            }
            if (x!=-1) break;
        }
        if (x==-1) break;

        finGrainGrow = false;

        while(!finGrainGrow){

            finGrainGrow = true;
            previousPoints.clear();
            previousPoints.ensureCapacity(growthPoints.size());
            for(int q=0;q<growthPoints.size();q++){
                previousPoints.add(q,growthPoints.get(q));
            }
            growthPoints = new ArrayList<Point>();

            for(int h = 0; h<previousPoints.size(); h++){
                j = (int)(previousPoints.get(h).getX()/stepSize);
                k = (int)(previousPoints.get(h).getY()/stepSize);
                try{
                    if(checkMisorientation(p[j][k],p[j-1][k]) && p[j-1][k].getGrainNum() ==-1){
                        grains.get(grainNum).add(p[j-1][k]);
                        growthPoints.add(p[j-1][k]);
                        p[j-1][k].setGrainNum(grainNum);
                        finGrainGrow = false;
                    }
                }
                catch(ArrayIndexOutOfBoundsException t){
                }
                try{
                    if(checkMisorientation(p[j][k],p[j+1][k]) && p[j+1][k].getGrainNum() ==-1){
                        grains.get(grainNum).add(p[j+1][k]);
                        growthPoints.add(p[j+1][k]);
                        p[j+1][k].setGrainNum(grainNum);
                        finGrainGrow = false;
                    }
                }
                catch(ArrayIndexOutOfBoundsException t){
                }
                try{
                    if(checkMisorientation(p[j][k],p[j][k-1]) && p[j][k-1].getGrainNum() ==-1){
                        grains.get(grainNum).add(p[j][k-1]);
                        growthPoints.add(p[j][k-1]);
                        p[j][k-1].setGrainNum(grainNum);
                        finGrainGrow = false;
                    }
                }
                catch(ArrayIndexOutOfBoundsException t){
                }
                try{
                    if(checkMisorientation(p[j][k],p[j][k+1]) && p[j][k+1].getGrainNum() ==-1){
                        grains.get(grainNum).add(p[j][k+1]);
                        growthPoints.add(p[j][k+1]);
                        p[j][k+1].setGrainNum(grainNum);
                        finGrainGrow = false;
                    }
                }
                catch(ArrayIndexOutOfBoundsException t){
                }
            }

        }
    }
    return grains;
}