Java – Finally Block

Finally block:

• Finally, block is used to close resources (file, database etc.) after use.
• Finally block executes whether or not an exception raised.

class Code {       public static void main(String[] args)       {                   try                   {                               // int a = 10/5 ; -> try-finally blocks execute.                               // int a = 10/0 ; -> catch-finally blocks execute.                               System.out.println(“Try Block”);                   }                   catch (Exception e)                   {                               System.out.println(“Catch Block”);                   }                   finally                   {                               System.out.println(“Finally Block”);                   }       } }

Why closing statements belongs to finally block?

• Resource releasing logic must be executed whether or not an exception raised.
• For example, in ATM Transaction – the machine should release the ATM card in success case or failure case.

Unchecked v/s Checked Exceptions:

Unchecked Exceptions:

• The Child exceptions of RuntimeException are called Unchecked.
• Unchecked exceptions occur when program not connected to any resource.
• Handling unchecked exception is optional.
• Compiler not giving any Error if we don’t handle Unchecked Exceptions.

Checked Exceptions:

• If the exception is not child of RuntimeException is called Checked.
• Checked Exceptions occur when program connected to other resource.
• Handling these exceptions is mandatory.
• If we don’t handle the exception – Compiler raise Error message.

General Syntax to Open and Close File or Database:(programs never compiles)

• We close the resources in finally block
• We need to check the resource is connected or not while closing it.
• We use if block for this check as follows

Resource – File

Resource – Database

static void main() {             File f = null;             try             {                         f = new File(“abc.txt”);                         print(“File opened”);             }             catch (Exception e)             {                         print(“No such file”);             }             finally             {                         if(f != null)                         {                                     f.close();                                     print(“File closed”);                         }             } }

static void main() {             Connection con = null;             try             {                         con = DriverManager….;                         print(“Connected);             }             catch (Exception e)             {                         print(“Connection Failed”);             }             finally             {                         if(con != null)                         {                                     con.close();                                     print(“DB closed”);                         }             } }