Create ReveresePolishStack, which is empty on creation.

Co-Authored-By: td1223

src/main/java/ic/doc/README.txt

@@ -1,2 +0,0 @@
-Put your implementation code in this directory. 
-Delete this file before submission.

src/main/java/ic/doc/ReversePolishStack.java

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+package ic.doc;
+
+public class ReversePolishStack {
+  public int getSize() {
+    return 0;
+  }
+}

src/test/java/ic/doc/README.txt

@@ -1,2 +0,0 @@
-Put your test code in this directory. 
-Delete this file before submission.

src/test/java/ic/doc/ReversePolishStackTest.java

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+package ic.doc;
+
+import org.junit.Test;
+
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.Matchers.is;
+
+public class ReversePolishStackTest {
+  final ReversePolishStack reversePolishStack = new ReversePolishStack();
+
+  @Test
+  public void reversePolishStackEmptyInitially() {
+    assertThat(reversePolishStack.getSize(), is(0));
+  }
+}