first commit

java/queue/ArrayQueueModule.java

@@ -0,0 +1,137 @@
+package queue;
+
+import java.util.function.Predicate;
+
+/**
+ * @author Doschennikov Nikita (me@fymio.us)
+ */
+public class ArrayQueueModule {
+    private static Object[] queue = new Object[4];
+    private static int head = 0;
+    private static int size = 0;
+
+    public static void enqueue(Object element) {
+        assert element != null : "Element must not be null";
+        ensureCapacity();
+        queue[(head + size) % queue.length] = element;
+        size++;
+    }
+
+    public static void push(Object element) {
+        assert element != null : "Element must not be null";
+        ensureCapacity();
+        head = (head - 1 + queue.length) % queue.length;
+        queue[head] = element;
+        size++;
+    }
+
+    public static Object element() {
+        assert size > 0 : "Queue is empty";
+        return queue[head];
+    }
+
+    public static Object peek() {
+        assert size > 0 : "Queue is empty";
+        return queue[(head + size - 1) % queue.length];
+    }
+
+    public static Object dequeue() {
+        assert size > 0 : "Queue is empty";
+        Object result = queue[head];
+        queue[head] = null;
+        head = (head + 1) % queue.length;
+        size--;
+        return result;
+    }
+
+    public static Object remove() {
+        assert size > 0 : "Queue is empty";
+        int tail = (head + size - 1) % queue.length;
+        Object result = queue[tail];
+        queue[tail] = null;
+        size--;
+        return result;
+    }
+
+    public static int size() {
+        return size;
+    }
+
+    public static boolean isEmpty() {
+        return size == 0;
+    }
+
+    public static void clear() {
+        queue = new Object[4];
+        head = 0;
+        size = 0;
+    }
+
+    public static int count(Object element) {
+        assert element != null : "Element must not be null";
+        int cnt = 0;
+        for (int i = 0; i < size; i++) {
+            if (element.equals(queue[(head + i) % queue.length])) {
+                cnt++;
+            }
+        }
+        return cnt;
+    }
+
+    public static int countIf(Predicate<Object> predicate) {
+        assert predicate != null : "Predicate must not be null";
+        int cnt = 0;
+        for (int i = 0; i < size; i++) {
+            if (predicate.test(queue[(head + i) % queue.length])) {
+                cnt++;
+            }
+        }
+        return cnt;
+    }
+
+    public static int indexIf(Predicate<Object> predicate) {
+        assert predicate != null : "Predicate must not be null";
+        for (int i = 0; i < size; i++) {
+            if (predicate.test(queue[(head + i) % queue.length])) {
+                return i;
+            }
+        }
+        return -1;
+    }
+
+    public static int lastIndexIf(Predicate<Object> predicate) {
+        assert predicate != null : "Predicate must not be null";
+        for (int i = size - 1; i >= 0; i--) {
+            if (predicate.test(queue[(head + i) % queue.length])) {
+                return i;
+            }
+        }
+        return -1;
+    }
+
+    public static int indexOf(Object element) {
+        assert element != null : "Predicate must not be null";
+        for (int i = 0; i < size; i++) {
+            if (queue[(head + i) % queue.length].equals(element)) return i;
+        }
+        return -1;
+    }
+
+    public static int lastIndexOf(Object element) {
+        assert element != null : "Predicate must not be null";
+        for (int i = size - 1; i >= 0; i--) {
+            if (queue[(head + i) % queue.length].equals(element)) return i;
+        }
+        return -1;
+    }
+
+    private static void ensureCapacity() {
+        if (size < queue.length) return;
+        Object[] newQueue = new Object[queue.length * 2];
+        for (int i = 0; i < size; i++) {
+            newQueue[i] = queue[(head + i) % queue.length];
+        }
+        queue = newQueue;
+        head = 0;
+    }
+}