first commit

java/queue/ArrayQueueADT.java

@@ -0,0 +1,150 @@
+package queue;
+
+import java.util.function.Predicate;
+
+/**
+ * @author Doschennikov Nikita (me@fymio.us)
+ */
+public class ArrayQueueADT {
+    private Object[] queue;
+    private int head;
+    private int size;
+
+    public ArrayQueueADT() {
+        queue = new Object[4];
+        head = 0;
+        size = 0;
+    }
+
+    public static ArrayQueueADT create() {
+        return new ArrayQueueADT();
+    }
+
+    public static void enqueue(ArrayQueueADT q, Object element) {
+        assert q != null && element != null : "Queue and element must not be null";
+        ensureCapacity(q);
+        q.queue[(q.head + q.size) % q.queue.length] = element;
+        q.size++;
+    }
+
+    public static void push(ArrayQueueADT q, Object element) {
+        assert q != null && element != null : "Queue and element must not be null";
+        ensureCapacity(q);
+        q.head = (q.head - 1 + q.queue.length) % q.queue.length;
+        q.queue[q.head] = element;
+        q.size++;
+    }
+
+    public static Object element(ArrayQueueADT q) {
+        assert q != null && q.size > 0 : "Queue must not be null and not be empty";
+        return q.queue[q.head];
+    }
+
+    public static Object peek(ArrayQueueADT q) {
+        assert q != null && q.size > 0 : "Queue must not be null and not be empty";
+        return q.queue[(q.head + q.size - 1) % q.queue.length];
+    }
+
+    public static Object dequeue(ArrayQueueADT q) {
+        assert q != null && q.size > 0 : "Queue must not be null and not be empty";
+        Object result = q.queue[q.head];
+        q.queue[q.head] = null;
+        q.head = (q.head + 1) % q.queue.length;
+        q.size--;
+        return result;
+    }
+
+    public static Object remove(ArrayQueueADT q) {
+        assert q != null && q.size > 0 : "Queue must not be null and not be empty";
+        int tail = (q.head + q.size - 1) % q.queue.length;
+        Object result = q.queue[tail];
+        q.queue[tail] = null;
+        q.size--;
+        return result;
+    }
+
+    public static int size(ArrayQueueADT q) {
+        assert q != null : "Queue must not be null";
+        return q.size;
+    }
+
+    public static boolean isEmpty(ArrayQueueADT q) {
+        assert q != null : "Queue must not be null";
+        return q.size == 0;
+    }
+
+    public static void clear(ArrayQueueADT q) {
+        assert q != null : "Queue must not be null";
+        q.queue = new Object[4];
+        q.head = 0;
+        q.size = 0;
+    }
+
+    public static int count(ArrayQueueADT q, Object element) {
+        assert q != null && element != null : "Queue and element must not be null";
+        int cnt = 0;
+        for (int i = 0; i < q.size; i++) {
+            if (element.equals(q.queue[(q.head + i) % q.queue.length])) {
+                cnt++;
+            }
+        }
+        return cnt;
+    }
+
+    public static int countIf(ArrayQueueADT q, Predicate<Object> predicate) {
+        assert q != null && predicate != null : "Queue and predicate must not be null";
+        int cnt = 0;
+        for (int i = 0; i < q.size; i++) {
+            if (predicate.test(q.queue[(q.head + i) % q.queue.length])) {
+                cnt++;
+            }
+        }
+        return cnt;
+    }
+
+    public static int indexIf(ArrayQueueADT q, Predicate<Object> predicate) {
+        assert q != null && predicate != null : "Queue and predicate must not be null";
+        for (int i = 0; i < q.size; i++) {
+            if (predicate.test(q.queue[(q.head + i) % q.queue.length])) {
+                return i;
+            }
+        }
+        return -1;
+    }
+
+    public static int lastIndexIf(ArrayQueueADT q, Predicate<Object> predicate) {
+        assert q != null && predicate != null : "Queue and predicate must not be null";
+        for (int i = q.size - 1; i >= 0; i--) {
+            if (predicate.test(q.queue[(q.head + i) % q.queue.length])) {
+                return i;
+            }
+        }
+        return -1;
+    }
+
+    public static int indexOf(ArrayQueueADT q, Object element) {
+        assert element != null : "Predicate must not be null";
+        for (int i = 0; i < q.size; i++) {
+            if (q.queue[(q.head + i) % q.queue.length].equals(element)) return i;
+        }
+        return -1;
+    }
+
+    public static int lastIndexOf(ArrayQueueADT q, Object element) {
+        assert element != null : "Predicate must not be null";
+        for (int i = q.size - 1; i >= 0; i--) {
+            if (q.queue[(q.head + i) % q.queue.length].equals(element)) return i;
+        }
+        return -1;
+    }
+
+    private static void ensureCapacity(ArrayQueueADT q) {
+        if (q.size < q.queue.length) return;
+        Object[] newQueue = new Object[q.queue.length * 2];
+        for (int i = 0; i < q.size; i++) {
+            newQueue[i] = q.queue[(q.head + i) % q.queue.length];
+        }
+        q.queue = newQueue;
+        q.head = 0;
+    }
+}