Concepts Archives - Page 11 of 14

Comparing java.util.Date with database time (java.sql.Timestamp) 1

Apr

5

2013

And so it happened. I stumbled again and this time I was hit by mere milliseconds. Yeah!!! One sure would find a few milliseconds really insignificant but it gave me a real pain in the a** for a while. All I did was to compare a “cron expression” time (a java.util.Date object) with the timestamp ...

Classloaders – back to basics…

Apr

5

2013

Regular java application running from command line involve three classloaders Bootstrap Classloader It is the parent of all the classloaders and loads the standard JDK classes in the lib directory of JRE (rt.jar and i18n.jar). All the “*. java ” classes are loaded by this loader. Extension Classloader It is the immediate child of bootstrap ...

Class Methods and Instance Methods

Apr

5

2013

S.No. Class Methods Instance Methods 1. Class methods are methods which are declared as static. The method can be called without creating an instance of the class Instance methods on the other hand require an instance of the class to exist before they can be called, so an instance of a class needs to be ...

Characters for formatting a dateTime as String

Apr

5

2013

Source Symbol Meaning Presentation Examples a am or pm marker Text Input am, AM, pm, PM. Output AM or PM d day in month (1-31) Number 1, 20 dd day in month (01-31) Number 01, 31 D day in year (1-366) Number 3, 80, 100 DD day in year (01-366) Number 03, 80, 366 ...

Can we execute a program without main() method in java?

Apr

5

2013

Yes, using static block (not possible from JDK 1.7 onwards) for example: class A { static { String name = getName(); System.out.println(name); } public static String getName() { return “project code bank”; } } output: project code bank Exception in thread “main” java.lang.NoSuchMethodError: main using System.exit(0) in the static we can ...

Autoboxing and Unboxing 1

Apr

5

2013

Autoboxing, introduced in Java 5, is the automatic conversion the Java compiler makes between the primitive (basic) types and their corresponding object wrapper classes (eg, int and Integer, double and Double, etc). The underlying code that is generated is the same, but autoboxing provides a sugar coating that avoids the tedious and hard-to-read casting typically ...

Attributes and Parameters in Servlets

Apr

5

2013

Attributes Parameters Types 1. Application/context 2. Request 3. Session 1. Application/context init parameters 2. Request parameters 3. Servlet init parameters Method to set setAttribute(String name, Object value) You CANNOT set Application and Servlet init parameters—they’re set in the DD, Return type Object String Method to get getAttribute(String name) return type of the method is Object getInitParameter(String name) ...

ArrayList and Vector

Apr

5

2013

java.util.Vector was introduced with the first version of java development kit (JDK 1.1) and java.util.ArrayList was introduced in java version 1.2 as a part of collections framework, later vector has also been retrofitted to implement List and became the part of the collections framework. Both ArrayList and Vector use array as a internal data structure and are dynamically resizable with default size zero and ...

‘RRRR’ versus ‘YYYY’

Apr

5

2013

The RRRR date format was provided to help people cope with Y2K issues. If the format is RR or RRRR and a two-digit year is given, then the year will be assumed to be prepended with ’19’ if the given year is between 50 and 99, or it will be assumed to be prepended with ...

I am programmer, I’ve no life 4

Apr

4

2013