need to get the pixel screen height

Question

I need to get the image position print string it's position and y+= _speed moves the image up the screen I need to descend the image if it reaches the screen height position

public void update()
{
    // put your code here
    double ypos;
    y += _speed;
    if (ypos = true) y -= _speed;
    else                   System.out.println(x + " is not positive");

}

Answer 1

I want to detect the screen edge with image

 public SeaHorse()
{
    // initialise instance variables
    super("models/billboard/billboard.obj", "textures/javaFish/Seahorse.png", 0.4);
    setPosition(1.0,1.0,1.0);
    setOrientation(90,0,0);