练习数据结构中Hashmap的使用方法，编写一个login小程序。
Review of hashing (from the lectures)
Study the two exercises discussed in the lectures. Download the source codes and the students.txt file (links given next to Lab 9 link).
HashMapDemo.java
Run the above with students.txt
HashMapDemo1.java
Run the above with a sample set of words, one word on each line, ending with “end”
Then complete the following exercise.
Exercise
Your friend is starting up a new web site that is going to have users register as members. He asks you to help implement an application that would validate a member’s login.
Your task is to write a program that reads a file containing the full name, username, and password for each user.
Create a hashmap with the username as key and the password as value. Create another hashmap with the username as key and full name as value.
After the file is read, prompt the user to enter the login name and password. If the password is incorrect, give the user two more chances. If the password is incorrect all three times, the program quits. If the login is successful, print a welcome message. Use the first hashmap to check the username and password match, and use the second hashmap to print the welcome message.
Here’s a sample input file:
Ichabod Crane icrane qwerty123
Brom Bones bbones pass456!
Emboar Pokemon epokemon password123
Rayquazza Pokemon rpokemon drow456
Cool Dude cdude gh456!32
Trend Chaser tchaser xpxo567!
Chuck Norris cnorris power332*
Drum Dude ddude jflajdljfped
In the above file, for example, Ichabod Crane is the full name, icrane is the username and qwerty123 is the password. In practice, the passwords are encrypted, but for this program, you can store them in plaintext.
Here are two sample runs of the program:
Sample Run 1
Login: rpokemon
Password: drow456
Login successful
Welcome Rayquazza Pokemon
In practice, the password is hidden when it is typed, but don’t worry about that in your program.
Sample Run2
Login: cdude
Password: trythis
Either the username or password is incorrect. You have 2 more attempts.
Login: cdude
Password: trythat
Either the username or password is incorrect. You have 1 more attempt.
Login: cdude
Password: 675rtht!
Sorry. Incorrect login. Please contact the system administrator.
What to submit: Source code, sample input file used, and sample runs of the program.