1) Singleton that every body knows
class Foo { private static Helper helper = null;
public static Helper getHelper() { if (helper == null) { helper = new Helper();
}
return helper;
}
private Foo(){} }
Analyzing point 1: Pros: Good for single threaded application
Cons: Gets real bad in multithreaded programs. Ex: Threads 1,2 will start at the same time and create two instances defeating the purpose. Proof: try syso(getHelper());
2) Basic fix:
class Foo { private static Helper helper = null;
public static synchronized Helper getHelper() { if (helper == null) { helper = new Helper();
}
return helper;
}
private Foo(){} }
Analyzing technique 2:
Pros: Wow!! fixes the cons of technique 1
Cons: Expensive. Imagine 50 Threads in your application and every time they invoke getHelper you pay the cost of synch and reduces application speed.
3) Lazy Fix:
class Foo { private static Helper helper = new Foo();
public static Helper getHelper() { return helper;
}
private Foo(){} }
Pros: Fixed it for MultiThreading. Loading static pieces once owned by class
Cons: UnNecessary creation of objects if not needed. Imagine you have a lot of classes with this fix and you want to create objects on meeting certain conditions, but this will all objects irrespective of conditions met
More techniques coming soon!!!
