Java: Document two FPs with unit tests.

java/ql/test/query-tests/Nullness/C.java

@@ -168,4 +168,44 @@ public class C {
       finalObj.hashCode(); // OK
     }
   }
+
+  private void verifyBool(boolean b) {
+    if (!b) {
+      throw new Exception();
+    }
+  }
+
+  public void ex13(int[] a) {
+    int i = 0;
+    boolean b = false;
+    Object obj = null;
+    while (a[++i] != 0) {
+      if (a[i] == 1) {
+        obj = new Object();
+        b = true;
+      } else if (a[i] == 2) {
+        verifyBool(b);
+        obj.hashCode(); // NPE - false positive
+      }
+    }
+  }
+
+  private void verifyNotNull(Object obj) {
+    if (obj == null) {
+      throw new Exception();
+    }
+  }
+
+  public void ex14(int[] a) {
+    int i = 0;
+    Object obj = null;
+    while (a[++i] != 0) {
+      if (a[i] == 1) {
+        obj = new Object();
+      } else if (a[i] == 2) {
+        verifyNotNull(obj);
+        obj.hashCode(); // NPE - false positive
+      }
+    }
+  }
 }