add_to_AccountTest.java

	public void testAccountExceptionDiffCaseFailed() {
		try {
			Account a = new Account("Hacker");
			fail(a.getName() + " isn't legal name");
		} catch (AccountException e) {
			assertEquals(e.getMessage(),
			        AccountException.NAME_TOO_SIMPLE);
		}
	}

	public void testAccountExceptionDiffCaseCorrect() {
		try {
	        Account a = new Account("c00l_hax0r");
	        assertEquals(a.getName(),"c00l_hax0r");
        } catch (AccountException e) {
	        fail(e.getName() + " is legal name"); 
        }
	}

module8.AccountException.java

package sef.module8.activity;

/**
 * This class represents the exception that can be thrown if the
 * name given to an Account instance violates naming rules
 * 
 * @author John Doe
 * 
 */
public class AccountException extends Exception {

	public static final String NAME_TOO_SHORT = "Name must be longer than 4 characters";
	public static final String NAME_TOO_SIMPLE = "Name must contain a combination of letters and numbers";

	private String name;

	/**
	 * Constructs an AcountException
	 * 
	 * @param message
	 *            The message to be set explaining the name
	 *            violation (see static attributes)
	 * @param name
	 *            The actual name
	 */
	public AccountException(String message, String name) {
		super(message);
		this.name = name;
	}

	/**
	 * Returns the name passed to this Account exception
	 * 
	 * @return
	 */
	public String getName() {
		return this.name;
	}

}

module8.activity.java

package sef.module8.activity;

import java.util.Calendar;
import java.util.HashMap;
import java.util.Map;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

/**
 * Thsi class represents a simple representation of an account
 * encapsulating a name
 * 
 * @author John Doe
 * 
 */
public class Account {

	private String name;

	final static int MIN_LENGTH = 4;

	/**
	 * Creates an Account object with the specified name. If the
	 * account name given violates the minimum requirements, then
	 * an AccountException is thrown
	 * 
	 * @param accountName
	 * @throws AccountException
	 */
	public Account(String accountName) throws AccountException {
		if (accountName.length() < MIN_LENGTH) {
			throw new AccountException(
			        AccountException.NAME_TOO_SHORT, accountName);
		}
		boolean flagL = false;
		boolean flagD = false;
		boolean flag = false;

		for (int i = 1; (i < accountName.length() && !flag); i++) {

			flagL = flagL
			        || Character.isLetter(accountName.charAt(i));
			flagD = flagD
			        || Character.isDigit(accountName.charAt(i));
			flag = flagL && flagD;

		}

		if (flag) {
			this.name = accountName;
		} else {
			throw new AccountException(
			        AccountException.NAME_TOO_SIMPLE, accountName);
		}
	}

	/**
	 * Returns the account name
	 * 
	 * @return the account name
	 */
	public String getName() {
		return this.name;
	}
}