Github user justinleet commented on a diff in the pull request:
https://github.com/apache/metron/pull/823#discussion_r153899916
--- Diff:
metron-stellar/stellar-common/src/main/java/org/apache/metron/stellar/dsl/functions/OrdinalFunctions.java
---
@@ -0,0 +1,93 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.metron.stellar.dsl.functions;
+
+import org.apache.metron.stellar.dsl.BaseStellarFunction;
+import org.apache.metron.stellar.dsl.Stellar;
+
+import java.util.Collections;
+import java.util.List;
+import java.util.stream.Collectors;
+
+public class OrdinalFunctions {
+
+ /**
+ * Stellar Function: MAX
+ * <p>
+ * Return the maximum value of a list of input values in a Stellar list
+ */
+ @Stellar(name = "MAX"
+ , description = "Returns the maximum value of a list of input
values"
+ , params = {"list_of_values - Stellar list of values to
evaluate. The list may only contain 1 type of object (only strings or only
numbers)" +
+ " and the objects must be comparable / ordinal"}
+ , returns = "The highest value in the list, null if the list
is empty or the input values could not be ordered")
+ public static class Max extends BaseStellarFunction {
+
+ @Override
+ public Object apply(List<Object> args) {
+ if (args.size() < 1 || args.get(0) == null) {
+ throw new IllegalStateException("MAX function requires at
least a Stellar list of values");
+ }
+ List list = (List<Object>) args.get(0);
+ return orderList(list, true);
+ }
+ }
+
+ /**
+ * Stellar Function: MIN
+ * <p>
+ * Return the minimum value of a list of input values in a Stellar list
+ */
+ @Stellar(name = "MIN"
+ , description = "Returns the minimum value of a list of input
values"
+ , params = {"list_of_values - Stellar list of values to
evaluate. The list may only contain 1 type of object (only strings or only
numbers)" +
+ " and the objects must be comparable / ordinal"}
+ , returns = "The lowest value in the list, null if the list is
empty or the input values could not be ordered")
+ public static class Min extends BaseStellarFunction {
+ @Override
+ public Object apply(List<Object> args) {
+ if (args.size() < 1 || args.get(0) == null) {
+ throw new IllegalStateException("MIN function requires at
least a Stellar list of values");
+ }
+ List list = (List<Object>) args.get(0);
+ return orderList(list, false);
+ }
+ }
+
+ private static Object orderList(List<Object> list, Boolean max) {
+ if (list.isEmpty()) {
+ return null;
+ }
+ List filteredList = (List<Object>) list.stream().filter(index ->
!(index == null)).collect(Collectors.toList());
+ if (filteredList.isEmpty()) {
+ return null;
+ }
+ try {
+ if (max) {
+ Collections.sort(filteredList,Collections.reverseOrder());
--- End diff --
Why not just use Collections.min() and Collections.max()?
---
