feat: add Lab4

Lab1/QueueTest.java

@@ -0,0 +1,23 @@
+class QueueTest {
+
+  public static void main(String[] args) {
+    CS2030STest i = new CS2030STest();
+    Queue<Integer> q = new Queue<Integer>(2);
+    i.expect("insert 4 into a queue of integer",
+        q.enq(4), true);
+    i.expect("insert 8 into a queue of integer",
+        q.enq(8), true);
+    i.expect("insert 0 into a full queue",
+        q.enq(0), false);
+    i.expect("remove 4 from queue",
+        q.deq(), 4);
+    i.expect("remove 8 from queue",
+        q.deq(), 8);
+    i.expect("cannot deque anymore",
+        q.deq(), null);
+    i.expectCompile("cannot deque a non-integer from a queue of integer",
+        "String s = new Queue<Integer>(3).deq();", false);
+    i.expectCompile("cannot insert a non-integer into a queue of integer",
+        "new Queue<Integer>(3).enqueue(false);", false);
+  }
+}