Model isNotEmpty from Apache Commons Collections

java/ql/src/semmle/code/java/dataflow/NullGuards.qll

@@ -5,6 +5,7 @@
 import java
 import SSA
 private import semmle.code.java.controlflow.internal.GuardsLogic
+private import semmle.code.java.frameworks.apache.Collections
 private import RangeUtils
 private import IntegerGuards
 
@@ -144,11 +145,7 @@ predicate nullCheckMethod(Method m, boolean branch, boolean isnull) {
   branch = false and
   isnull = false
   or
-  (
+  m instanceof MethodApacheCollectionsIsNotEmpty and
-    m.getDeclaringType().hasQualifiedName("org.apache.commons.collections4", "CollectionUtils") or
-    m.getDeclaringType().hasQualifiedName("org.apache.commons.collections", "CollectionUtils")
-  ) and
-  m.hasName("isNotEmpty") and
   branch = true and
   isnull = false
   or

java/ql/src/semmle/code/java/frameworks/apache/Collections.qll

@@ -0,0 +1,18 @@
+/** Definitions related to the Apache Commons Collections library. */
+
+import java
+private import semmle.code.java.dataflow.FlowSteps
+private import semmle.code.java.dataflow.ExternalFlow
+
+/**
+ * The method `isNotEmpty` in either `org.apache.commons.collections.CollectionUtils`
+ * or `org.apache.commons.collections4.CollectionUtils`.
+ */
+class MethodApacheCollectionsIsNotEmpty extends Method {
+  MethodApacheCollectionsIsNotEmpty() {
+    this.getDeclaringType()
+        .hasQualifiedName(["org.apache.commons.collections", "org.apache.commons.collections4"],
+          "CollectionUtils") and
+    this.hasName("isNotEmpty")
+  }
+}