Java Questions

Constructor is not a special method.

Constructor is block of code that is executed automatically whenever object of the class is created.

File[] listFiles();

this method returns list of files stored in a directory.

It is the ability of an object to behave differently on different situations for the same message.

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 table of data representing a database result set, which is usually generated by executing a statement that queries the database.

ResultSet object maintains a cursor pointing to its current row of data. Initially the cursor is positioned before the first row. The next method moves the cursor to the next row, and because it returns false when there are no more rows in the ResultSet object, it can be used in a while loop to iterate through the result set.

Interface data is static data why bcoz interface supports multiple inheritance.

if inteface data is non-static then there is chance for replication of the data (bcoz of replication of data ambiguity problem occurs )

The JVM performs three main tasks:

• Loads code

• Verifies code

• Executes code

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.