Create Stack.java

Stack.java

@@ -0,0 +1,49 @@
+public class Stack<T> {
+    private static final int DEFAULT_CAPACITY = 10;
+    private Object[] elements;
+    private int size;
+
+    public Stack() {
+        elements = new Object[DEFAULT_CAPACITY];
+        size = 0;
+    }
+
+    public void push(T item) {
+        ensureCapacity();
+        elements[size++] = item;
+    }
+
+    @SuppressWarnings("unchecked")
+    public T pop() {
+        if (isEmpty()) {
+            throw new IllegalStateException("Stack is empty");
+        }
+        T item = (T) elements[--size];
+        elements[size] = null; // Help with garbage collection
+        return item;
+    }
+
+    public T peek() {
+        if (isEmpty()) {
+            throw new IllegalStateException("Stack is empty");
+        }
+        @SuppressWarnings("unchecked")
+        T item = (T) elements[size - 1];
+        return item;
+    }
+
+    public boolean isEmpty() {
+        return size == 0;
+    }
+
+    public int size() {
+        return size;
+    }
+
+    private void ensureCapacity() {
+        if (size == elements.length) {
+            int newCapacity = elements.length * 2;
+            elements = Arrays.copyOf(elements, newCapacity);
+        }
+    }
+}