Java Questions

Autoboxing is the process of converting a primitive type data into its corresponding wrapper class object instance.

Example:

Integer number = new Integer (100); // number is now refers to the object 100

Unboxing is the process of converting a wrapper instance into a primitive type.

Example: 

Integer number = new Integer (100); 

int num = number;// without type casting number would be changed into int type

A thread is a lightweight subprocess, a smallest unit of processing. It is a separate path of execution. It shares the memory area of process.

As shown in the above figure, thread is executed inside the process. There is context-switching between the threads. There can be multiple processes inside the OS and one process can have multiple threads.

Top level class is also called outer class. It is not defined inside any class.

Ex:

class A {  //top level class

}

To use an iterator to traverse through the contents of a collection, follow these steps:

- Obtain an iterator to the start of the collection by calling the collections iterator() method.

- Set up a loop that makes a call to hasNext(). Have the loop iterate as long as hasNext() returns true.

- Within the loop, obtain each element by calling next().

Dynamic binding is orthogonal to dynamic linking. Binding refers to the linking of a procedure call to the code to be executed in response to the call. Dynamic binding It is associated with polymorphism and inheritance, it(also known as late binding) means that the code associated with a given procedure call is not known until the time of the call at run-time.

Wrapped classes are classes that allow primitive types to be accessed as objects.

By using overloading we can add new functionality to the sub class.

For inserting, deleting, and locating elements in a Map, the HashMap offers the best alternative. If, however, you need to traverse the keys in a sorted order, then TreeMap is your better alternative. Depending upon the size of your collection, it may be faster to add elements to a HashMap, then convert the map to a TreeMap for sorted key traversal.