The Finally block in java is used along with the try-catch statements.
The usual structure is
try {
.....
} catch(Exception e){
....
} finally {
.....
}
In the finally block we usually have code that is used to perform clean up activities corresponding to the code in the try block. When an exception occurs in the try block control comes to the catch block and the rest of the code in the try block would not execute. In such cases we may need to have some code that cleans up the objects that we created/used in the try block.
No matter what happens, the code inside the finally block would definitely execute.
The best use of finally block is when we are connecting to the database. In the try block we would have the statements that instantiate the connection, prepared statement, result set etc. If the query fails then all these objects would be left open and the code would continue. So in the finally block we usually nullify these statements so that even in case of an error the unused objects are cleared.
Example:
Connection con;
PreparedStatment PS;
ResultSet rs;
try{
con = ConnectionManager.getConnection();
PS = con.prepareStatement(query);
rs = PS.executyQuery();
......
} catch (Exception e){
e.printStackTrace();
} finally {
con.close();
PS.close();
}
In case of an error the connection & prepared statement objects would remain open if we do not have the finally block.
Tip: Whatever code we have inside the finally block would be run definitely if the try block is invoked. We can even use the finally block to check if the try block was reached and executed. If the try executes then we can rest assured that the finally would also get executed.
Sun's Java Tutorial gives a few situations where a finally block will not execute.
"Note: If the JVM exits while the try or catch code is being executed, then the finally block will notexecute. Likewise, if the thread executing the try or catch code is interrupted or killed, the finally block willnot execute even though the application as a whole continues."
This method calls the exit method in class Runtime and terminates the JVM. This method never returns normally and finally is never called.
try {
System.out.println("hello");
System.exit(0);
} finally {
System.out.println("bye");
} // try-finally
Finally block is a block that is always executed . It is mainly used to perform some important tasks such as closing connection stream etc.
If you include system.exit(0); before the finally block in your code then execution flow will stop and finally block will not be executed.
The first name of the Java Programming was Oak. It then went by the game Green and finally Java from Java coffee.
In computer programming, a block or code block is a lexical structure of source code which is grouped together. In Java it is sed in the same way: to group code and separate it from the rest.
A Synchronized block is a block of code enclosed by the {} braces that has a synchronized keyword before it. This block of code is similar to a synchronized method and only one thread can access it at a time.
A component is a Reusable building block .
Theoretically, the finally block will execute no matter what. But practically, the following scenarios can prevent the execution of the finally block. * The death of thread * Use of system.exit() * Turning off the power to CPU * An exception arising in the finally block itself
use of finally block is optional in java.if u want to clean up ur code (means u want to close any connection)after exception handling then go for finally block.if not then also your code will run fine.so finally block is optional in java.
The final and finally keywords have no impact on the return type of a method in Java.
The first name of the Java Programming was Oak. It then went by the game Green and finally Java from Java coffee.
The first name of the Java Programming was Oak. It then went by the game Green and finally Java from Java coffee.
In computer programming, a block or code block is a lexical structure of source code which is grouped together. In Java it is sed in the same way: to group code and separate it from the rest.
Try block is followed by finally block as an alternative . But usually it is followed by a catch block. Both are equivalent.
A Synchronized block is a block of code enclosed by the {} braces that has a synchronized keyword before it. This block of code is similar to a synchronized method and only one thread can access it at a time.
Why does this happen? Because the people who designed Java said this should be so. They wanted a place to put cleanup code which was (almost) guaranteed to run no matter what exceptions were thrown along the way.
You can only explicitly escape from a finally block by returning out of it. A break statement is not allowed there.
A component is a Reusable building block .
to provide an action in case the code block in the try statement fails.
Genaerally every try block maintain the one finally block or atleast one catch block or both. It mean try { try{ try{ } or } or } finally { catch(....) { catch(...){ } } } catch(.....) { : } finally{ : } Hear whenever we declar the try block without catch or finally bocks it show the compile time error like ' try without catch or finally' and also it is not possible to declare the any statements in between the try ,catch and finally blocks. ex: try{ } System.out.println("statement"); finally { } The above example show the compile time error 'try without catch or finally'. " Hear the finally block must be execute after excuting the try or catch block. Hence the finally block is used to release the resources like closing the streams and closing the jdbc connections." Hence in exception handling we use one finally block for one try block to release the resources.