deltaTime = (System.nanoTime() - lastDeltaTime) / 1_000_000_000.0D;
lastDeltaTime = System.nanoTime();

 public int fps; private int frames; private long fpsTimer; public double deltaTime; private double lastDeltaTime; public boolean calculatePerformance; public Thread thread = new Thread() { public void run() { while(running) { // Update, Render, etc. if(calculatePerformance) calculatePerformance(); } } }; private final void calculatePerformance() { frames++; // Add 1 to frames each update. if(System.currentTimeMillis() - fpsTimer >= 1000L) { // If 1 second has passed. fpsTimer = System.currentTimeMillis(); // Update timer to current time. fps = frames; // Set fps to frames frames = 0; // Reset frames } deltaTime = (System.nanoTime() - lastDeltaTime) / 1_000_000_000.0D; // Set delta time from last delta time lastDeltaTime = System.nanoTime(); // Set last deltaTime to current delta Time }