completed part2

src/main/java/StackArray/ObjectStack.java

@@ -5,12 +5,43 @@ import java.util.Arrays;
 /**
  * Expand the ArrayList implementation of stack here to use an Object[] array.  Still implement push, pop, and isEmpty.
  * Remember, you might need to resize the stack in the push method.
+ *
  * @param <E>
  */
 public class ObjectStack<E> {
+
     private Object[] elements;
+    private int top;
+    private final static int EMPTY = -1;
+    private final static int DEFAULT_Capacity = 10;
 
     public ObjectStack() {
+        this(DEFAULT_Capacity);
+    }
+
+    public ObjectStack(int initialCapacity) {
+        elements = new Object[initialCapacity];
+        top = EMPTY;
+    }
 
+    public boolean isEmpty() {
+        return (top == EMPTY);
     }
+
+    @SuppressWarnings("unchecked")
+    public Object pop() {
+        if (top == EMPTY) {
+            throw new IndexOutOfBoundsException();
+        }
+        return elements[top--];
+    }
+
+    public void push(Object o) {
+        elements[++top] = o;
+    }
+
 }
+
+
+
+

src/test/java/StackArray/ObjectStackTest.java

@@ -1,39 +1,39 @@
-//package StackArray;
-//
-//import org.junit.Assert;
-//import org.junit.Test;
-//
-//public class ObjectStackTest {
-//    @Test
-//    public void testPushingGrowsTheStack() throws Exception {
-//        // Given an empty stack
-//        ObjectStack<String> stack = new ObjectStack<>();
-//        // Assert that it is empty.
-//        Assert.assertEquals(true, stack.isEmpty());
-//        // When we push something onto the stack
-//        stack.push("foobar");
-//        // Then it shouldn't be empty
-//        Assert.assertEquals(false, stack.isEmpty());
-//    }
-//
-//    @Test
-//    public void testPushingAndPoppingOrder() throws Exception {
-//        // Given an empty stack
-//        ObjectStack<String> stack = new ObjectStack<>();
-//        // When we push two elements on it
-//        stack.push("foo");
-//        stack.push("bar");
-//        // Then we should see them returned in the correct order
-//        Assert.assertEquals("bar", stack.pop());
-//        Assert.assertEquals("foo", stack.pop());
-//    }
-//
-//    @Test(expected = IndexOutOfBoundsException.class)
-//    public void testPopFirst() throws Exception {
-//        // Given an empty stack
-//        ObjectStack<String> stack = new ObjectStack<>();
-//        // When it's popped
-//        stack.pop();
-//        // Then we should get an exception
-//    }
-//}
+package StackArray;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+public class ObjectStackTest {
+    @Test
+    public void testPushingGrowsTheStack() throws Exception {
+        // Given an empty stack
+        ObjectStack<String> stack = new ObjectStack<>();
+        // Assert that it is empty.
+        Assert.assertEquals(true, stack.isEmpty());
+        // When we push something onto the stack
+        stack.push("foobar");
+        // Then it shouldn't be empty
+        Assert.assertEquals(false, stack.isEmpty());
+    }
+
+    @Test
+    public void testPushingAndPoppingOrder() throws Exception {
+        // Given an empty stack
+        ObjectStack<String> stack = new ObjectStack<>();
+        // When we push two elements on it
+        stack.push("foo");
+        stack.push("bar");
+        // Then we should see them returned in the correct order
+        Assert.assertEquals("bar", stack.pop());
+        Assert.assertEquals("foo", stack.pop());
+    }
+
+    @Test(expected = IndexOutOfBoundsException.class)
+    public void testPopFirst() throws Exception {
+        // Given an empty stack
+        ObjectStack<String> stack = new ObjectStack<>();
+        // When it's popped
+        stack.pop();
+        // Then we should get an exception
+    }
+}