Make ConverterManager.getInstance() init thread-safe. (#776)

JodaOrg · Apr 5, 2024 · 34197d2 · 34197d2
1 parent 290a451
commit 34197d2
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Showing 2 changed files with 10 additions and 8 deletions.
diff --git a/src/main/java/org/joda/time/convert/ConverterManager.java b/src/main/java/org/joda/time/convert/ConverterManager.java
@@ -81,15 +81,14 @@
 public final class ConverterManager {
 
     /**
-     * Singleton instance, lazily loaded to avoid class loading.
+     * Holds the singleton instance, lazily loaded to avoid class loading.
      */
-    private static ConverterManager INSTANCE;
+    private static final class LazyConverterManagerHolder {
+        static final ConverterManager INSTANCE = new ConverterManager();
+    }
 
     public static ConverterManager getInstance() {
-        if (INSTANCE == null) {
-            INSTANCE = new ConverterManager();
-        }
-        return INSTANCE;
+        return LazyConverterManagerHolder.INSTANCE;
     }
 
     private ConverterSet iInstantConverters;

diff --git a/src/test/java/org/joda/time/convert/TestConverterManager.java b/src/test/java/org/joda/time/convert/TestConverterManager.java
@@ -127,9 +127,12 @@ public void testSingleton() throws Exception {
         Constructor con = cls.getDeclaredConstructor((Class[]) null);
         assertEquals(1, cls.getDeclaredConstructors().length);
         assertEquals(true, Modifier.isProtected(con.getModifiers()));
+
+        Class holderCls = Class.forName(cls.getName() + "$LazyConverterManagerHolder");
+        assertEquals(true, Modifier.isPrivate(holderCls.getModifiers()));
 
-        Field fld = cls.getDeclaredField("INSTANCE");
-        assertEquals(true, Modifier.isPrivate(fld.getModifiers()));
+        Field fld = holderCls.getDeclaredField("INSTANCE");
+        assertEquals(true, Modifier.isFinal(fld.getModifiers()));
     }
 
     //-----------------------------------------------------------------------