How to update LG O1 P500 from Android Froyo(2.2.1) to Gingerbread(2.3.3)

Step 1) Go to link LG Mobile Phone Support
Step 2) Download the LG Mobile Support Tool to your PC.
Step 3) Run it and double click on 'install drivers'.
Step 4) Now install drivers & LG PC Suite
Step 5) Connect your phone with USB cable and give IMEI number or model.
Step 6) Click on start Updating. Takes some time and phone will be upgraded.
Note: Phone got switched off in my case (Don't know if that was intended.
Step 7) Remove the USB connection and switch on the phone. It takes few minutes to start.
Step 8) Connect phone to PC and close the LG Mobile update Tool, if you have opted for backup it will restore the details.

Constraints of a Database table

Queries used to find the constraints are :-

a) select * from USER_CONSTRAINTS where table_name = &table_name

b) select * from all_constraints where table_name = &table_name

c) select * from all_ind_columns where table_name = &table_name

Singleton class in JAVA

Singleton pattern used when we want to allow only a single instance of a class can be created inside our application. Using this pattern ensures that a class only have a single instance by protecting the class creation process, by setting the class constructor into private access modifier.

To get the class instance, the singleton class can provide a method for example a getInstance() method, this will be the only method that can be accessed to get the instance.

01.package new.mypack.sample

02.

03.public class Service {

04. private static Service instance = new Service();

05.

06. private Service() {

07. }

08.

09. public static synchronized Service getInstance() {

10. return instance;

11. }

12.

13. @Override

14. protected Object clone() throws CloneNotSupportedException {

15. throw new CloneNotSupportedException("Clone is not allowed.");

16. }

17.}

There are some rules that need to be followed when we want to implement a singleton.

1. From the example code above you can see that a singleton has a static variable to keep it sole instance.
2. You need to set the class constructor into private access modifier. By this you will not allowed any other class to create an instance of this singleton because they have no access to the constructor.
3. Because no other class can instantiate this singleton how can we use it? the answer is the singleton should provide a service to it users by providing some method that returns the instance, for example getInstance().
4. When we use our singleton in a multi threaded application we need to make sure that instance creation process not resulting more that one instance, so we add a synchronized keywords to protect more than one thread access this method at the same time.
5. It is also advisable to override the clone() method of the java.lang.Object class and throw CloneNotSupportedException so that another instance cannot be created by cloning the singleton object.