how would you create a new entity at the coordinates of your mouse by pressing a key on the keyboard?

1. public Entity(float startx,float starty){
2.     x = startx;
3.     y = starty;
4.     speed = 5;
5.     selected = moving = false;
6.   }

1. void keyPressed(){
2.       entities.add(new Entity(mouseX,mouseY));
3. }

as well, when i put a background against the moving blocks, the movement of the blocks creates a copy of the entities behind their movement like a line of squares. any ideas on how to stop this from happening?