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Update RightLazySingleton.java #3

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Update RightLazySingleton.java #3

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12 changes: 10 additions & 2 deletions src/main/java/org/abqjug/javapatterns/singleton/lazy/RightLazySingleton.java
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Original file line number Diff line number Diff line change
Expand Up @@ -11,9 +11,17 @@ public class RightLazySingleton {
private RightLazySingleton() {
}

public static synchronized RightLazySingleton getInstance() {
public static RightLazySingleton getInstance() {
if (instance == null) {
instance = new RightLazySingleton();
// Only synchronize once (i.e. we don't want to context switch every time getInstance is called!)
synchronized(RightLazySingleton.class) {
// Need the 2nd null check in case 1 or more threads were waiting for the lock, while
// the first thread assigned the instance. So, if 1 or more threads got past the first
// null check, they will not get past the 2nd when the first thread releases the lock.
if (instance == null) {
instance = new RightLazySingleton();
}
}
}
return instance;
}
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