add examples on deffered operation and manual staging

Author: elebras1

examples/src/main/java/com/github/elebras1/flecs/examples/DeferredOperationsExample.java

@@ -0,0 +1,39 @@
+package com.github.elebras1.flecs.examples;
+
+import com.github.elebras1.flecs.Entity;
+import com.github.elebras1.flecs.Query;
+import com.github.elebras1.flecs.World;
+import com.github.elebras1.flecs.examples.components.Health;
+
+public class DeferredOperationsExample {
+
+    public static void main(String[] args) {
+        try(World world = new World()) {
+            world.component(Health.class);
+
+            for(int i = 0; i < 1000; i++) {
+                Entity entity = world.obtainEntity(world.entity("entity_" + i));
+                entity.set(new Health(i));
+            }
+
+            Query query = world.query().with(Health.class).build();
+
+            world.deferBegin();
+            for(int i = 10; i < 20; i++) {
+                long entityId = world.lookup("entity_" + i);
+                Entity entity = world.obtainEntity(entityId);
+                entity.remove(Health.class);
+            }
+            if(query.count() != 1000) {
+                throw new RuntimeException("Expected 1000 entities, but got " + query.count());
+            }
+            world.deferEnd();
+
+            if(query.count() != 990) {
+                throw new RuntimeException("Expected 990 entities, but got " + query.count());
+            }
+
+            query.close();
+        }
+    }
+}

examples/src/main/java/com/github/elebras1/flecs/examples/ManualStagingExample.java

@@ -0,0 +1,57 @@
+package com.github.elebras1.flecs.examples;
+
+import com.github.elebras1.flecs.Entity;
+import com.github.elebras1.flecs.Query;
+import com.github.elebras1.flecs.World;
+import com.github.elebras1.flecs.examples.components.Health;
+
+import java.lang.foreign.MemorySegment;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.concurrent.ExecutionException;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.Future;
+
+import static jdk.internal.jrtfs.JrtFileAttributeView.AttrID.size;
+
+public class ManualStagingExample {
+    private static final int THREADS = 4;
+
+    public static void main(String[] args) {
+        ExecutorService executor = Executors.newFixedThreadPool(THREADS);
+        List<Future<?>> futures = new ArrayList<>();
+
+        try (World world = new World()) {
+            world.setStageCount(THREADS);
+            world.component(Health.class);
+
+            for (int i = 0; i < 1000; i++) {
+                Entity entity = world.obtainEntity(world.entity("entity_" + i));
+                entity.set(new Health(i));
+            }
+
+            for (int i = 0; i < THREADS; i++) {
+                final int stageId = i;
+                futures.add(executor.submit(() -> {
+                    World stage = world.getStage(stageId);
+                    for(int j = stageId * 250; j < (stageId + 1) * 250; j++) {
+                        long entityId = world.lookup("entity_" + j);
+                        Entity entity = stage.obtainEntity(entityId);
+                        entity.set(new Health(j));
+                    }
+                }));
+            }
+
+            for (Future<?> f : futures) {
+                f.get();
+            }
+
+            world.merge();
+            executor.shutdown();
+
+        } catch (ExecutionException | InterruptedException e) {
+            throw new RuntimeException(e);
+        }
+    }
+}