apache commons lang3 string utils model (#1346)

Summary:
Small model for a couple of StringUtils functions

Pull Request resolved: https://github.com/facebook/infer/pull/1346

Reviewed By: ngorogiannis

Differential Revision: D25638009

Pulled By: jvillard

fbshipit-source-id: 01db6d09e

infer/models/java/src/org/apache/commons/lang3/NOTICE.txt

@@ -0,0 +1,5 @@
+Apache Commons Lang
+Copyright 2001-2020 The Apache Software Foundation
+
+This product includes software developed at
+The Apache Software Foundation (https://www.apache.org/).

infer/models/java/src/org/apache/commons/lang3/StringUtils.java

@@ -0,0 +1,53 @@
+/*
+ * 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.
+ */
+
+/* 
+ * The method below are copied verbatim from:
+ * https://github.com/apache/commons-lang/blob/master/src/main/java/org/apache/commons/lang3/StringUtils.java
+ * to provide a model for biabduction analysis
+ */
+
+package org.apache.commons.lang3;
+
+public final class StringUtils {
+
+  public static boolean isNotEmpty(final CharSequence cs) {
+    return !isEmpty(cs);
+  }
+
+  public static boolean isEmpty(final CharSequence cs) {
+    return cs == null || cs.length() == 0;
+  }
+
+  public static boolean isBlank(final CharSequence cs) {
+    final int strLen = length(cs);
+    if (strLen == 0) {
+      return true;
+    }
+    for (int i = 0; i < strLen; i++) {
+      if (!Character.isWhitespace(cs.charAt(i))) {
+        return false;
+      }
+    }
+    return true;
+  }
+
+  public static int length(final CharSequence cs) {
+    return cs == null ? 0 : cs.length();
+  }
+
+}