feat: added MovingAverageQueue

Author: AlmasB

fxgl-core/src/main/kotlin/com/almasb/fxgl/core/collection/MovingAverageQueue.kt

@@ -0,0 +1,35 @@
+/*
+ * FXGL - JavaFX Game Library. The MIT License (MIT).
+ * Copyright (c) AlmasB (almaslvl@gmail.com).
+ * See LICENSE for details.
+ */
+
+package com.almasb.fxgl.core.collection
+
+/**
+ * A "buffer" queue that keeps track of the moving average based on all elements.
+ *
+ * @author Almas Baimagambetov (almaslvl@gmail.com)
+ */
+class MovingAverageQueue(private val maxSize: Int) {
+
+    private var sum = 0.0
+
+    var average = 0.0
+        private set
+
+    private val queue = ArrayDeque<Double>(maxSize)
+
+    fun put(item: Double) {
+        if (queue.size == maxSize) {
+            val oldItem = queue.removeFirst()
+
+            sum -= oldItem
+        }
+
+        queue.addLast(item)
+
+        sum += item
+        average = sum / queue.size
+    }
+}

fxgl-core/src/test/kotlin/com/almasb/fxgl/core/collection/MovingAverageQueueTest.kt

@@ -0,0 +1,53 @@
+/*
+ * FXGL - JavaFX Game Library. The MIT License (MIT).
+ * Copyright (c) AlmasB (almaslvl@gmail.com).
+ * See LICENSE for details.
+ */
+@file:Suppress("JAVA_MODULE_DOES_NOT_DEPEND_ON_MODULE")
+package com.almasb.fxgl.core.collection
+
+import org.hamcrest.MatcherAssert.assertThat
+import org.hamcrest.Matchers
+import org.junit.jupiter.api.BeforeEach
+import org.junit.jupiter.api.Test
+
+/**
+ *
+ * @author Almas Baimagambetov (almaslvl@gmail.com)
+ */
+class MovingAverageQueueTest {
+
+    private lateinit var queue: MovingAverageQueue
+
+    @BeforeEach
+    fun setUp() {
+        queue = MovingAverageQueue(100)
+    }
+
+    @Test
+    fun `Average`() {
+        repeat(50) {
+            queue.put(25.0)
+        }
+
+        assertThat(queue.average, Matchers.closeTo(25.0, 0.0001))
+
+        repeat(10) {
+            queue.put(27.0)
+        }
+
+        assertThat(queue.average, Matchers.closeTo(25.33, 0.01))
+
+        repeat(40) {
+            queue.put(27.0)
+        }
+
+        assertThat(queue.average, Matchers.closeTo(26.0, 0.0001))
+
+        repeat(100) {
+            queue.put(30.0)
+        }
+
+        assertThat(queue.average, Matchers.closeTo(30.0, 0.0001))
+    }
+}