BAEL-2820 Transforming Optional of an Empty String into Empty Optional (#6634)

core-java-11/pom.xml

@@ -14,6 +14,14 @@
         <version>1.0.0-SNAPSHOT</version>
     </parent>
 
+    <dependencies>
+        <dependency>
+            <groupId>com.google.guava</groupId>
+            <artifactId>guava</artifactId>
+            <version>${guava.version}</version>
+        </dependency>
+    </dependencies>
+
     <build>
         <plugins>
             <plugin>
@@ -31,6 +39,7 @@
     <properties>
         <maven.compiler.source.version>11</maven.compiler.source.version>
         <maven.compiler.target.version>11</maven.compiler.target.version>
+        <guava.version>27.1-jre</guava.version>
     </properties>
 
 </project>

core-java-11/src/test/java/com/baeldung/EmptyStringToEmptyOptionalUnitTest.java

@@ -0,0 +1,32 @@
+package com.baeldung;
+
+import com.google.common.base.Strings;
+import org.junit.Assert;
+import org.junit.Test;
+
+import java.util.Optional;
+import java.util.function.Predicate;
+
+public class EmptyStringToEmptyOptionalUnitTest {
+
+    @Test
+    public void givenEmptyString_whenFilteringOnOptional_thenEmptyOptionalIsReturned() {
+        String str = "";
+        Optional<String> opt = Optional.ofNullable(str).filter(s -> !s.isEmpty());
+        Assert.assertFalse(opt.isPresent());
+    }
+
+    @Test
+    public void givenEmptyString_whenFilteringOnOptionalInJava11_thenEmptyOptionalIsReturned() {
+        String str = "";
+        Optional<String> opt = Optional.ofNullable(str).filter(Predicate.not(String::isEmpty));
+        Assert.assertFalse(opt.isPresent());
+    }
+
+    @Test
+    public void givenEmptyString_whenPassingResultOfEmptyToNullToOfNullable_thenEmptyOptionalIsReturned() {
+        String str = "";
+        Optional<String> opt = Optional.ofNullable(Strings.emptyToNull(str));
+        Assert.assertFalse(opt.isPresent());
+    }
+}