In social networking websites, people link to their friends to form a social network. Write a program that uses HashMaps to store the data for such a network. Your program should read from a file that specifies the network connections for different usernames. The file should have the following format to specify a link:

source_usernamefriend_username

There should be an entry for each link, one per line. Here is a sample file for five usernames:

iba java_guru

iba crisha

iba ducky

crisha java_guru

crisha iba

ducky java_guru

ducky iba

java_guru iba

java_guru crisha

java_guru ducky

wittless java_guru

In this network, everyone links to java_guru as a friend. iba is friends with java_guru , crisha , and ducky . Note that links are not bidirectional; wittless links with java_guru but java_guru does not link with wittless.

First, create a User class that has an instance variable to store the user’s name and another instance variable that is of type HashSet<User>. The HashSet<User> variable should contain references to the User objects that the current user links to. For example, for the user iba there would be three entries, for java_guru, crisha, and ducky. Second, create a HashMap<String, User> instance variable in your main class that is used to map from a username to the corresponding User object. Your program should ]do the following:

• Upon startup, read the data file and populate the HashMap and HashSet data structures according to the links specified in the file.

• Allow the user to enter a name.

• If the name exists in the map, then output all usernames that are one link away from the user entered.

• If the name exists in the map, then output all usernames that are two links away from the user entered. To accomplish this in a general way, you might consider writing a recursive subroutine.

Do not forget that your User class must override the hashCode and equals methods.