Add: generic queue implementation.

KyleScharnhorst · KyleScharnhorst · commit 7ea76784d8ac · 2017-10-07T20:40:48.000-07:00
Uses an arraylist its underlying datastructure.
diff --git a/data_structures/Queues/GenericArrayListQueue.java b/data_structures/Queues/GenericArrayListQueue.java
@@ -0,0 +1,42 @@
+import java.util.ArrayList;
+
+public class GenericArrayListQueue<T> {
+    ArrayList<T> _queue = new ArrayList<T>();
+
+    private boolean hasElements() {
+        return !_queue.isEmpty();
+    }
+
+    public T peek() {
+        T result = null;
+        if(this.hasElements()) { result = _queue.get(0); }
+        return result;
+    }
+
+    public boolean add(T element) {
+        return _queue.add(element);
+    }
+
+    public T poll() {
+        T result = null;
+        if(this.hasElements()) { result = _queue.remove(0); }
+        return result;
+    }
+
+    public static void main(String[] args) {
+        GenericArrayListQueue<Integer> queue = new GenericArrayListQueue<Integer>();
+        System.out.println("Running...");
+        assert queue.peek() == null;
+        assert queue.poll() == null;
+        assert queue.add(1) == true;
+        assert queue.peek() == 1;
+        assert queue.add(2) == true;
+        assert queue.peek() == 1;
+        assert queue.poll() == 1;
+        assert queue.peek() == 2;
+        assert queue.poll() == 2;
+        assert queue.peek() == null;
+        assert queue.poll() == null;
+        System.out.println("Finished.");
+    }
+}
