Here is the hammer code :
public void act()
{
checkMouse();
}
public void checkMouse()
{
MouseInfo mouse = Greenfoot.getMouseInfo();
if(mouse!=null){
int button = mouse.getButton();
if(button == 1) {
int mouseX=mouse.getX();
int mouseY=mouse.getY();
setLocation(mouseX, mouseY);
}
}
}