Java Questions

Java Collections Framework provides a well designed set of interfaces and classes that support operations on a collections of objects. The most basic interfaces that reside in the Java Collections Framework are:

Collection, which represents a group of objects known as its elements.

Set, which is a collection that cannot contain duplicate elements.

List, which is an ordered collection and can contain duplicate elements.

Map, which is an object that maps keys to values and cannot contain duplicate keys.

Executing two or more blocks (threads) of a program at a time is called MultiThreading.

java bean is a reusable component, where as the servlet is the java program which extends the server capability. 

When we create string with new() Operator, it’s created in heap and not added into string pool while String created using literal are created in String pool itself which exists in PermGen area of heap.

String s = new String("Test");

does not put the object in String pool , we need to call String.intern() method which is used to put them into String pool explicitly. its only when you create String object as String literal e.g. String s = "Test" Java automatically put that into String pool.

Final method is a method defined in the super class with final modifier.

We cannot overriding final method of super class in the sub class.

EX:

 Class Sample {

   final void funOne() {

   }

   void funTwo() {

   }

}

Class Sub extends Sample {

  void funOne() { // overriding is not allowed

  }

  viod funTwo() { //overriding is allowed

  }

}

Executing more than one program simultaniously.(i.e at time)

Ex:

Windows media player  is a program

Internet explorer(IE) is another program executing both the programs  at a time is called multi tasking.

In single virtual machine,JVM passes arguments only by value.

Instance is an object not an attribute