fix: Remove unnecessary and possibly not threadsafe flag (iluwatar#1811)

mortezaadi · web-flow · commit 3126ad31066e · 2021-09-07T21:43:47.000+03:00
diff --git a/singleton/src/main/java/com/iluwatar/singleton/ThreadSafeDoubleCheckLocking.java b/singleton/src/main/java/com/iluwatar/singleton/ThreadSafeDoubleCheckLocking.java
@@ -36,16 +36,12 @@ public final class ThreadSafeDoubleCheckLocking {
 
   private static volatile ThreadSafeDoubleCheckLocking instance;
 
-  private static boolean flag = true;
-
   /**
    * private constructor to prevent client from instantiating.
    */
   private ThreadSafeDoubleCheckLocking() {
     // to prevent instantiating by Reflection call
-    if (flag) {
-      flag = false;
-    } else {
+    if (instance != null) {
       throw new IllegalStateException("Already initialized.");
     }
   }
diff --git a/singleton/src/main/java/com/iluwatar/singleton/ThreadSafeLazyLoadedIvoryTower.java b/singleton/src/main/java/com/iluwatar/singleton/ThreadSafeLazyLoadedIvoryTower.java
@@ -34,9 +34,7 @@ public final class ThreadSafeLazyLoadedIvoryTower {
 
   private ThreadSafeLazyLoadedIvoryTower() {
     // Protect against instantiation via reflection
-    if (instance == null) {
-      instance = this;
-    } else {
+    if (instance != null) {
       throw new IllegalStateException("Already initialized.");
     }
   }

Original file line number	Diff line number	Diff line change
`@@ -34,9 +34,7 @@ public final class ThreadSafeLazyLoadedIvoryTower {`
`34`	`34`
`35`	`35`	`private ThreadSafeLazyLoadedIvoryTower() {`
`36`	`36`	`// Protect against instantiation via reflection`
`37`		`- if (instance == null) {`
`38`		`- instance = this;`
`39`		`- } else {`
	`37`	`+ if (instance != null) {`
`40`	`38`	`throw new IllegalStateException("Already initialized.");`
`41`	`39`	`}`
`42`	`40`	`}`