Bael 9484 update article "attaching values to java enums" (#18917)

* Update Element2.java

* Update Element3.java

* Update Element4.java

* Update Element2UnitTest.java

Author: dvohra09

core-java-modules/core-java-lang-oop-types/src/main/java/com/baeldung/enums/values/Element2.java

@@ -1,5 +1,7 @@
 package com.baeldung.enums.values;
 
+import java.util.Objects;
+
 /**
  * The simple enum has been enhanced to add the name of the element.
  */
@@ -12,8 +14,11 @@ public enum Element2 {
     C("Carbon"),
     N("Nitrogen"),
     O("Oxygen"),
-    F("Flourine"),
-    NE("Neon");
+    // Fixed: "Flourine" -> "Fluorine"
+    F("Fluorine"), 
+    NE("Neon"),
+    // Added: Dedicated UNKNOWN member
+    UNKNOWN("Unknown Element"); 
 
     /** a final variable to store the label, which can't be changed */
     public final String label;
@@ -30,15 +35,17 @@ private Element2(String label) {
      * Look up Element2 instances by the label field. This implementation iterates through 
      * the values() list to find the label.
      * @param label The label to look up
-     * @return The Element2 instance with the label, or null if not found.
+     * @return The Element2 instance with the label, or UNKNOWN if not found.
      */
     public static Element2 valueOfLabel(String label) {
         for (Element2 e2 : values()) {
-            if (e2.label.equals(label)) {
+            // Fixed: Used Objects.equals for null-safe comparison
+            if (Objects.equals(e2.label, label)) {
                 return e2;
             }
         }
-        return null;
+        // Fixed: Return UNKNOWN instead of null
+        return UNKNOWN; 
     }
 
     /**

core-java-modules/core-java-lang-oop-types/src/main/java/com/baeldung/enums/values/Element3.java

@@ -15,11 +15,11 @@ public enum Element3 {
     C("Carbon"),
     N("Nitrogen"),
     O("Oxygen"),
-    F("Flourine"),
+    // Fixed: "Flourine" -> "Fluorine"
+    F("Fluorine"), 
     NE("Neon");
 
-    /** 
-     * A map to cache labels and their associated Element3 instances.
+    /** * A map to cache labels and their associated Element3 instances.
      * Note that this only works if the labels are all unique!
      */
     private static final Map<String, Element3> BY_LABEL = new HashMap<>();

core-java-modules/core-java-lang-oop-types/src/main/java/com/baeldung/enums/values/Element4.java

@@ -15,10 +15,11 @@ public enum Element4 implements Labeled {
     C("Carbon", 6, 12.011f),
     N("Nitrogen", 7, 14.007f),
     O("Oxygen", 8, 15.999f),
-    F("Flourine", 9, 18.998f),
+    // Fixed: "Flourine" -> "Fluorine"
+    F("Fluorine", 9, 18.998f), 
     NE("Neon", 10, 20.180f);
-    /** 
-     * Maps cache labels and their associated Element3 instances.
+    
+    /** * Maps cache labels and their associated Element3 instances.
      * Note that this only works if the values are all unique!
      */
     private static final Map<String, Element4> BY_LABEL = new HashMap<>();
@@ -55,7 +56,7 @@ public String label() {
     }
 
     /**
-     * Look up Element2 instances by the label field. This implementation finds the
+     * Look up Element4 instances by the label field. This implementation finds the
      * label in the BY_LABEL cache.
      * @param label The label to look up
      * @return The Element4 instance with the label, or null if not found.
@@ -65,7 +66,7 @@ public static Element4 valueOfLabel(String label) {
     }
 
     /**
-     * Look up Element2 instances by the atomicNumber field. This implementation finds the
+     * Look up Element4 instances by the atomicNumber field. This implementation finds the
      * atomicNUmber in the cache.
      * @param number The atomicNumber to look up 
      * @return The Element4 instance with the label, or null if not found.
@@ -75,7 +76,7 @@ public static Element4 valueOfAtomicNumber(int number) {
     }
 
     /**
-     * Look up Element2 instances by the atomicWeight field. This implementation finds the
+     * Look up Element4 instances by the atomicWeight field. This implementation finds the
      * atomic weight in the cache.
      * @param weight the atomic weight to look up
      * @return The Element4 instance with the label, or null if not found.

core-java-modules/core-java-lang-oop-types/src/test/java/com/baeldung/enums/values/Element2UnitTest.java

@@ -1,8 +1,3 @@
-/*
- * To change this license header, choose License Headers in Project Properties.
- * To change this template file, choose Tools | Templates
- * and open the template in the editor.
- */
 package com.baeldung.enums.values;
 
 import org.junit.After;
@@ -43,10 +38,22 @@ public void tearDown() {
     @Test
     public void whenLocatebyLabel_thenReturnCorrectValue() {
         for (Element2 e2 : Element2.values()) {
+            // FIX: Skip UNKNOWN element, as it's not meant to be looked up by its own label in this test
+            if (e2 == Element2.UNKNOWN) { 
+                continue;
+            }
             assertSame(e2, Element2.valueOfLabel(e2.label));
         }
     }
 
+    @Test
+    public void whenLocatebyUnknownLabel_thenReturnUNKNOWN() {
+        // New test to ensure an unknown label returns the UNKNOWN constant
+        assertSame(Element2.UNKNOWN, Element2.valueOfLabel("Unobtainium"));
+        // Test for null label, which should also return UNKNOWN
+        assertSame(Element2.UNKNOWN, Element2.valueOfLabel(null));
+    }
+
     /**
      * Test of toString method, of class Element2.
      */