EnumUtils.getEnumSystemProperty(...).

src/changes/changes.xml

@@ -49,6 +49,8 @@ The <action> type attribute can be add,update,fix,remove.
     <!-- FIX -->
     <action issue="LANG-1645" type="fix" dev="aherbert" due-to="Alex Herbert">NumberUtils.createNumber to recognise hex integers prefixed with +.</action>
     <action issue="LANG-1646" type="fix" dev="aherbert" due-to="Alex Herbert">NumberUtils.createNumber to return requested floating point type for zero.</action>
+    <!-- ADD -->
+    <action                   type="add" dev="ggregory" due-to="Gary Gregory">EnumUtils.getEnumSystemProperty(...).</action>
   </release>
 
   <release version="3.12.0" date="2021-02-26" description="New features and bug fixes (Java 8).">

src/main/java/org/apache/commons/lang3/EnumUtils.java

@@ -294,6 +294,28 @@ public class EnumUtils {
         return map;
     }
 
+    /**
+     * <p>
+     * Gets the enum for the class in a system property, returning {@code defaultEnum} if not found.
+     * </p>
+     *
+     * <p>
+     * This method differs from {@link Enum#valueOf} in that it does not throw an exception for an invalid enum name.
+     * </p>
+     *
+     * @param <E> the type of the enumeration
+     * @param enumClass the class of the enum to query, not null
+     * @param propName the system property key for the enum name, null returns default enum
+     * @param defaultEnum the default enum
+     * @return the enum, default enum if not found
+     * @since 3.13.0
+     */
+    public static <E extends Enum<E>> E getEnumSystemProperty(final Class<E> enumClass, final String propName,
+        final E defaultEnum) {
+        return enumClass == null || propName == null ? defaultEnum
+            : getEnum(enumClass, System.getProperty(propName), defaultEnum);
+    }
+
     /**
      * <p>Checks if the specified name is a valid enum for the class.</p>
      *

src/test/java/org/apache/commons/lang3/EnumUtilsTest.java

@@ -343,6 +343,21 @@ public class EnumUtilsTest {
         assertFalse(test.containsKey("PURPLE"));
     }
 
+    @Test
+    public void test_getEnumSystemProperty() {
+        final String key = getClass().getName();
+        System.setProperty(key, Traffic.RED.toString());
+        try {
+            assertEquals(Traffic.RED, EnumUtils.getEnumSystemProperty(Traffic.class, key, null));
+            assertEquals(Traffic.RED, EnumUtils.getEnumSystemProperty(Traffic.class, "?", Traffic.RED));
+            assertEquals(Traffic.RED, EnumUtils.getEnumSystemProperty(null, null, Traffic.RED));
+            assertEquals(Traffic.RED, EnumUtils.getEnumSystemProperty(null, "?", Traffic.RED));
+            assertEquals(Traffic.RED, EnumUtils.getEnumSystemProperty(Traffic.class, null, Traffic.RED));
+        } finally {
+            System.getProperties().remove(key);
+        }
+    }
+
     @Test
     public void test_isValidEnum() {
         assertTrue(EnumUtils.isValidEnum(Traffic.class, "RED"));