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Welcome you at the JAVA BOOTS.

Its a place where u find,discuss,share common problems,coding strategies, design principles etc in java and related technologies. I keep sharing my learnings here. Hope it will be helpful to all.

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When to use getClass() and instanceOf in Java

getClass() only gives equality if two objects belong to same class whereas instanceOf works for subtype also. If two objects of different classes are checked for equal, then we use instanceOf . But once you use instanceOf at some level in the class hierarchy everything below it must use instanceOf or you will violatate the symmetry clause of equals contract.  e.g. any list can be equal to any list as long they have same elements iun the same order. So any List implementation equals() method must do instanceOf and not getclass() and then compare. On the other hand, it only make sense for na instance of class X to be equal to another instance of class X ( and not any subclass ) , then use getClass().
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How class.forName loads the Database Driver in JDBC

When Class.forName() is called with an argument like this: Class.forName("org.gjt.mm.mysql.Driver"); the classloader attempts to load and link the Driver class in the “org.gjt.mm.mysql” package and if successful, the static initializer is run. The MySQL Driver static initializer looks like this: static {   try {     java.sql.DriverManager.registerDriver(new Driver());   } catch (SQLException E) {     throw new RuntimeException("Can't register driver!");   } } So it calls a static method in the java.sql.DriverManager class which apparently registers a copy of itself when it loads.   To understand the why you have to look at the next line in the initial code example: Connection con = DriverManager.getConnection(url,   "myLogin", "myPassword"); The DriverManager class returns a database connection given a JDBC URL string, a username and a password. In order to create that connect...
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Why Time gets truncated with ResutSet getDate() function.

Recently I stuck in an issue on populating date from stored procedure. I am reading a date from a resultset using rs.getDate(), storing in a java.util.Date instance variable and displaying on the screen. Java.util.Date  mydate = rs.getDate(1); Output is only date while time is truncated.  But why …! That confused me a lot. So I google it. Spending lot of time in reading blogs, oracle docs and trying different things on oracle server like checking  NLS_DATE_FORMAT, I am not able to get the time. Next I come across a Timestamp thing in Resultset class. Rs.getTimestamp (int colIndex) When I use it, I immediately get the time.  Now, the important question, why the resultset function getDate() does not return the Time. Now my search is preety narrow. What I found is :- In java, we have java.util.Date for java.sq.Date . So functionalities available in sql.Date are also available in util.Date. But there is one difference, sql.Date stores only Date and not Time ...
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