generic stack complete

src/main/java/StackArray/GenericStack.java

@@ -1,28 +1,41 @@
-//package StackArray;
-//
-//import java.util.Arrays;
-//import java.util.Stack;
-//
-///**
-// * Expand the ArrayList implementation of stack here to use an E[] array.  Still implement push, pop, and isEmpty.
-// * Remember, you might need to resize the stack in the push method.
-// * @param <E>
-// */
-//public class GenericStack<E> {
-//    private E[] elements;
-//
-//    GenericStack<String> myStack = new GenericStack<>();
-//
-//    public GenericStack() {
-//    }
-//
-//    public E isEmpty() {
-//
-//    }
-//
-//    public void push(E foobar) {
-//    }
-//
-//    public E pop() {
-//    }
-//}
+package StackArray;
+
+import java.util.Arrays;
+import java.util.Stack;
+
+/**
+ * Expand the ArrayList implementation of stack here to use an E[] array.  Still implement push, pop, and isEmpty.
+ * Remember, you might need to resize the stack in the push method.
+ * @param <E>
+ */
+public class GenericStack<E> {
+    private E[] elements;
+
+   // GenericStack<String> myStack = new GenericStack<>();
+
+    public GenericStack() {
+        elements = (E[]) new Object[0];
+
+        //casting to just an object: (not array)
+        // element = (E) new Object;
+
+    }
+
+    public boolean isEmpty() {
+
+        return elements.length==0;
+
+    }
+
+    public void push(E foobar) {
+        elements= Arrays.copyOf(elements, elements.length+1);
+        elements[elements.length-1] = foobar;
+    }
+
+
+    public E pop() {
+        E lastElement = (E) elements[elements.length-1];
+        elements=Arrays.copyOf(elements,elements.length-1);
+        return lastElement;
+    }
+}

src/test/java/StackArray/GenericStackTest.java

@@ -1,41 +1,41 @@
-//package StackArray;
-//
-//import org.junit.Assert;
-//import org.junit.Test;
-//
-//public class GenericStackTest {
-//    @Test
-//    public void testPushingGrowsTheStack() throws Exception {
-//        // Given an empty stack
-//        GenericStack<String> stack = new GenericStack<>();
-//
-//        // 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
-//        GenericStack<String> stack = new GenericStack<>();
-//        // 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
-//        GenericStack<String> stack = new GenericStack<>();
-//        // When it's popped
-//        stack.pop();
-//        // Then we should get an exception
-//    }
-//
-//}
+package StackArray;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+public class GenericStackTest {
+    @Test
+    public void testPushingGrowsTheStack() throws Exception {
+        // Given an empty stack
+        GenericStack<String> stack = new GenericStack<>();
+
+        // 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
+        GenericStack<String> stack = new GenericStack<>();
+        // 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
+        GenericStack<String> stack = new GenericStack<>();
+        // When it's popped
+        stack.pop();
+        // Then we should get an exception
+    }
+
+}