Is it square

Given coordinates of four points, say if they will form a square or not
https://github.com/mission-peace/interview/blob/master/src/com/interview/misc/FourPointsFormSquare.java
* Given four points in any order determine if they form a square
* Test cases
* Less than or more than 4 points in input
* Points could be in any quadrants e.it neg and pos allowed
    public boolean isSquare(Cordinate[] cordinates){
        Cordinate startPoint = cordinates[0];
        int a1 = distanceSquare(startPoint, cordinates[1]);
        int a2 = distanceSquare(startPoint, cordinates[2]);
        int a3 = distanceSquare(startPoint, cordinates[3]);
     
     
        if(a1 == a2){ //then 0,3 is diagonal
            return compare(cordinates[3],cordinates[1],cordinates[2],a1,a3);
        }else if(a1 == a3){
            return compare(cordinates[2],cordinates[1],cordinates[3],a1,a2);
        }else if(a2 == a3){
            return compare(cordinates[1],cordinates[2],cordinates[3],a2,a1);
        }else{
            return false;
        }
    }
 
    private boolean compare(Cordinate startPoint, Cordinate point1, Cordinate point2,int len, int diag){
        if(2*len != diag){ //?
            return false;
        }
        int a1 = distanceSquare(startPoint,point1);
        int a2 = distanceSquare(startPoint,point2);
        if(a1 != len || a2 != len){
            return false;
        }
        return true;
    }
 
    private int distanceSquare(Cordinate c1, Cordinate c2){
        return (int)(Math.pow(Math.abs(c1.x - c2.x) ,2) +
                Math.pow(Math.abs(c1.y-c2.y), 2));
    }