Answer Posted / lokesh

Singleton design pattern is a a creational pattern to
dictate how and when objects get created and it's main
purpose is to ensure that a class has only one instance

Example:
#define NULL 0

class Singleton
{
private:
Singleton(Singleton&){}
Singleton& operator =(Singleton&);
int nValue;
static Singleton* pSingleton;
Singleton():nValue(10)
{
}
public:
static Singleton*Instance()
{

if(NULL == pSingleton)
{
pSingleton = new Singleton();
}
return pSingleton;
}
void setValue(int val)
{
nValue = val;
}
int getValue()
{
return nValue;
}
};
Singleton* Singleton::pSingleton = NULL;

int main(int argc, char* argv[])
{
Singleton *abc = NULL;
cout<<Singleton::Instance()->getValue()<<endl;
Singleton::Instance()->setValue(20);

Singleton *xyz = NULL;
cout<<xyz->Instance()->getValue()<<endl;
Singleton *sss = Singleton::Instance();
return 0;
}

Why have we declared the instance reference volatile?

1069

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Explain what is good design?

1140

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What are creational design patterns?

1141

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Why singleton beans are not thread safe?

1133

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Give me example of observer design pattern?

1178

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Which design patterns have you used in your project ?

1093

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What is the difference between factory and strategy design pattern?

1101

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What are the main usage of the patterns?

1149

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What are the categories in which the design patterns can be divided?

1206

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What is the concurrency design pattern?

1207

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What is proxy in design pattern?

1104

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5.Develop an entity relationships diagram that identifies physical entity relationships.

2875

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What are the languages used in the design pattern?

1113

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How do you choose a design pattern?

1090

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Is singleton an anti pattern?

1063

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