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java/org/apache/el/stream/Optional.java

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+/*
+ * 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.el.stream;
+
+import javax.el.ELException;
+import javax.el.LambdaExpression;
+
+import org.apache.el.util.MessageFactory;
+
+public class Optional {
+
+    private final Object obj;
+
+    static final Optional EMPTY = new Optional(null);
+
+    Optional(Object obj) {
+        this.obj = obj;
+    }
+
+
+    public Object get() throws ELException {
+        if (obj == null) {
+            throw new ELException(MessageFactory.get("stream.optional.empty"));
+        } else {
+            return obj;
+        }
+    }
+
+
+    public void ifPresent(LambdaExpression le) {
+        if (obj != null) {
+            le.invoke(obj);
+        }
+    }
+
+
+    public Object orElse(Object other) {
+        if (obj == null) {
+            return other;
+        } else {
+            return obj;
+        }
+    }
+
+
+    public Object orElseGet(Object le) {
+        if (obj == null) {
+            // EL 3.0 specification says parameter is LambdaExpression but it
+            // may already have been evaluated. If that is the case, the
+            // original parameter will have been checked to ensure it was a
+            // LambdaExpression before it was evaluated.
+
+            if (le instanceof LambdaExpression) {
+                return ((LambdaExpression) le).invoke((Object[]) null);
+            } else {
+                return le;
+            }
+        } else {
+            return obj;
+        }
+    }
+}