java how to calculate fps

To calculate the frames per second (FPS) in Java, you can keep track of the time elapsed between successive frames and divide the number of frames by the elapsed time.

Here is an example of how to calculate FPS in a simple game loop:

long startTime = System.nanoTime();
int frameCount = 0;
while (gameRunning) {
    // update game state and render frame
    frameCount++;
    long elapsedTime = System.nanoTime() - startTime;
    if (elapsedTime >= 1000000000) { // 1 second
        float fps = (float) frameCount / (elapsedTime / 1000000000f);
        System.out.println("FPS: " + fps);
        startTime = System.nanoTime();
        frameCount = 0;
    }
}

In this example, the startTime variable is initialized to the current time in nanoseconds using the System.nanoTime method. The frameCount variable is used to keep track of the number of frames that have been rendered.

The game loop runs until the gameRunning variable is true. Inside the loop, the game state is updated and a frame is rendered. The frameCount variable is incremented to keep track of the number of frames that have been rendered.

After each frame is rendered, the elapsed time is calculated by subtracting the startTime from the current time using the System.nanoTime method. If the elapsed time is greater than or equal to 1 second (1000000000 nanoseconds), the FPS is calculated by dividing the frameCount by the elapsed time in seconds. The FPS is then printed to the console using the println method of the System.out object. The startTime and frameCount variables are reset to start a new FPS measurement.

This example will print the FPS to the console every second, based on the number of frames rendered during that time.

Note that this is a simple example and may not be suitable for all applications. You may need to adjust the time interval for measuring the FPS and the method of calculating the FPS based on the specific needs of your application.