Optimized version of the mass sprite sheet loading where no memory spike happens

MemoryUsageOptimizedClient.java

import com.badlogic.gdx.Game;
import com.badlogic.gdx.Gdx;
import com.badlogic.gdx.backends.lwjgl.LwjglApplication;
import com.badlogic.gdx.backends.lwjgl.LwjglApplicationConfiguration;
import com.badlogic.gdx.files.FileHandle;
import com.badlogic.gdx.graphics.GL20;
import com.badlogic.gdx.graphics.Texture;
import com.badlogic.gdx.graphics.g2d.Animation;
import com.badlogic.gdx.graphics.g2d.BitmapFont;
import com.badlogic.gdx.graphics.g2d.SpriteBatch;
import com.badlogic.gdx.graphics.g2d.TextureRegion;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.lang.management.ManagementFactory;
import java.util.*;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.stream.IntStream;

public class MemoryUsageOptimizedClient {

    private static final Logger logger = LoggerFactory.getLogger(MemoryUsageOptimizedClient.class);

    public static void main(String... args){
        LwjglApplicationConfiguration config = new LwjglApplicationConfiguration();

        config.width = 1900;
        config.height = 1280;

        final int[] renderingCounter = {0};

        new LwjglApplication(new Game() {

            private static final int nbAnimations = 500;
            private static final int nbDistinctSheets = 500;

            private BitmapFont font;
            private SpriteBatch batch;
            private Map<AbstractMap.SimpleEntry, Animation<TextureRegion>> testAnimations;
            private List<TextureRegion[][]> spriteSheets;
            private double stateTime;

            @Override
            public void create() {
                System.out.println("Starting to create!");

                this.batch = new SpriteBatch();
                this.font = new BitmapFont();
                this.stateTime = 0;
                this.testAnimations = new HashMap<>();

                //Explicit full gc calls not really necessary here, but just in case
                System.gc();
                System.out.println("Getting ready to load textures, memory = " + (getTotalMemory() - getFreeMemory()) / 1024 / 1024 + " MB");
                initSpriteSheets();
                System.gc();
                System.out.println("Finished loading textures, memory = " + (getTotalMemory() - getFreeMemory()) / 1024 / 1024 + " MB");

                System.out.println("App created, now rendering.");
            }

            private void initSpriteSheets() {
                this.spriteSheets = new ArrayList<>();
                batch.begin();
                IntStream.iterate(0, n -> n+1).limit(nbDistinctSheets).forEach(n -> {
                    System.out.println("Loading sheet #" + n + "...");
                    Texture texture = new Texture(new FileHandle("./pv-client/src/test/resources/ant_running_17frames.png"));
                    TextureRegion[][] singleDimensionalArray = TextureRegion.split(texture, 384, 384);
                    this.spriteSheets.add(singleDimensionalArray);

                    TextureRegion[][] electedSheet = spriteSheets.get(n);
                    Animation<TextureRegion> animation = new Animation<>(18, electedSheet[0]);
                    animation.setPlayMode(Animation.PlayMode.LOOP);
                    int spreadFactor = 1000 / nbAnimations;
                    int x = (int)Math.round(Math.random()*(nbAnimations/2) * spreadFactor);
                    int y = (int)Math.round(Math.random()*(nbAnimations/2) * spreadFactor);
                    testAnimations.put(new AbstractMap.SimpleEntry(x, y), animation);

                    batch.draw(electedSheet[0][0], 0,0);

                    if(n % 100 == 0) {
                        System.out.println("Every 10th sheet loaded, memory = " + (getTotalMemory() - getFreeMemory()) / 1024 / 1024 + " MB");
                    }

                });
                batch.end();
            }

            @Override
            public void render() {
                renderingCounter[0]++;
                if(renderingCounter[0] % 100 == 0) {
                    System.out.println("Main render loop, memory = " + (getTotalMemory() - getFreeMemory()) / 1024 / 1024 + " MB");
                }
                actuallyRender();
            }

            private void actuallyRender() {
                Gdx.gl20.glClearColor(0f / 255f, 0f / 255f, 0f / 255f, 1f);
                //Gdx.gl20.glClearColor(255f / 255f, 255f / 255f, 255f / 255f, 1f);
                Gdx.gl20.glClear(GL20.GL_COLOR_BUFFER_BIT);

                this.stateTime+=Gdx.graphics.getDeltaTime()*1024;
                batch.begin();
                AtomicInteger currentIdx = new AtomicInteger();
                testAnimations.entrySet().forEach(e -> {
                    currentIdx.getAndIncrement();
                    float floatStateTime = (float) (stateTime + currentIdx.get() * 1024);
                    //System.out.println("Drawing from sheet #");
                    TextureRegion keyFrame = e.getValue().getKeyFrame(floatStateTime);
                    //System.out.println("time=" + floatStateTime + "; idx=" + testAnimation.getKeyFrameIndex(floatStateTime) + " -> u=" + keyFrame.getU() + "; v=" + keyFrame.getV() + "; u2=" + keyFrame.getU2() + "; v2=" + keyFrame.getV2() + "; ");
                    batch.draw(keyFrame, (Integer)e.getKey().getKey(), (Integer)e.getKey().getValue());
                });
                batch.end();

                drawFps();
            }

            private void drawFps() {
                int width = Gdx.graphics.getWidth();
                int height = Gdx.graphics.getHeight();
                batch.getProjectionMatrix().setToOrtho2D(0, 0, width, height);
                batch.begin();
                font.draw(batch, "FPS: " + Gdx.graphics.getFramesPerSecond(), 50, height - 50);
                batch.end();
            }

            private long getFreeMemory() {
                return ((com.sun.management.OperatingSystemMXBean)
                        ManagementFactory.getOperatingSystemMXBean()).getFreePhysicalMemorySize();
            }

            private long getTotalMemory() {
                return ((com.sun.management.OperatingSystemMXBean)
                        ManagementFactory.getOperatingSystemMXBean()).getTotalMemorySize();
            }

        });

    }
}