Hi Manu,
By making the Instance variable *volatile*, you can over come this issue.
This also has been mentioned in the reference link that you pointed
out ("Fixing
Double-Checked Locking using Volatile")[1]
class Foo {
private volatile Instance instance = null;
public Helper getInstance() {
if (instance == null) {
synchronized(MyClass.class) {
if (instance == null)
instance = new Instance();
}
}
return instance;
}
}
[1] http://www.cs.umd.edu/~pugh/java/memoryModel/DoubleCheckedLocking.html
Regards,
Firzhan
On Fri, Dec 19, 2014 at 7:00 PM, Gimantha Bandara <[email protected]> wrote:
>
> Hi,
>
> What about the singleton implementation using java enum? enum provides
> inbuilt thread safety. But still it works only for jdk 6 or later versions.
>
> On Fri, Dec 19, 2014 at 6:09 PM, Udara Liyanage <[email protected]> wrote:
>>
>> Hi,
>>
>> Several places have several methods. However I like the way of having an
>> inner static class. Java make sure a class is load only once, thus only one
>> object is created.
>>
>>
>> 1. class Singleton {
>> 2. private static class InstanceHolder {
>> 3. public static Singleton instance = new Singleton();
>> 4. }
>> 5.
>> 6. public static Singleton getInstance() {
>> 7. return InstanceHolder.instance;
>> 8. }
>> 9. }
>>
>>
>> On Fri, Dec 19, 2014 at 3:19 PM, Manuranga Perera <[email protected]> wrote:
>>>
>>>
>>> ---------- Forwarded message ----------
>>> From: Manuranga Perera <[email protected]>
>>> Date: Fri, Dec 19, 2014 at 3:15 PM
>>> Subject: What is the recommended way to initialize singleton
>>> To: dev <[email protected]>
>>> Cc: Afkham Azeez <[email protected]>, Sameera Jayasoma <[email protected]>,
>>> Sameera Perera <[email protected]>, Ruchira Wageesha <[email protected]>
>>>
>>> Following kind of double locking code doesn't work [1] for singletons.
>>> (please remove this if you see it in any place in the platform)
>>>
>>> if(instance == null) {
>>> synchronized(MyClass.class) {
>>> if(instance == null) {
>>> instance = new MyClass();
>>> }
>>> }
>>> }
>>> return instance;
>>>
>>>
>>> There are multiple ways we can do this right. What is the best practice
>>> for defining singletons in unavoidable situations?
>>>
>>> [1]
>>> http://www.cs.umd.edu/~pugh/java/memoryModel/DoubleCheckedLocking.html
>>>
>>> --
>>> With regards,
>>> *Manu*ranga Perera.
>>>
>>> phone : 071 7 70 20 50
>>> mail : [email protected]
>>>
>>>
>>> --
>>> With regards,
>>> *Manu*ranga Perera.
>>>
>>> phone : 071 7 70 20 50
>>> mail : [email protected]
>>>
>>> --
>>> You received this message because you are subscribed to the Google
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>>>
>>
>>
>> --
>>
>> Udara Liyanage
>> Software Engineer
>> WSO2, Inc.: http://wso2.com
>> lean. enterprise. middleware
>>
>> web: http://udaraliyanage.wordpress.com
>> phone: +94 71 443 6897
>>
>> --
>> You received this message because you are subscribed to the Google Groups
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>>
>
>
> --
> Gimantha Bandara
> Software Engineer
> WSO2. Inc : http://wso2.com
> Mobile : +94714961919
>
> --
> You received this message because you are subscribed to the Google Groups
> "WSO2 Engineering Group" group.
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>
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