PhoneBook

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import static java.lang.System.out;
import java.util.LinkedHashMap;
import java.util.Map;

/**
 *
 * @author Aamir khan
 */
public class PhoneBook {

    public static void main(String[] args) throws IOException {

        //Constant
        final short NUMBER_LENGTH = 10;

        //Create Map
        Map<String, Long> m = new LinkedHashMap<>();

        //vars
        String name, num;
        Long Phno;
        BufferedReader console = new BufferedReader(new InputStreamReader(System.in));

        //Menu
        while (true) {
            out.println("1 Add Phone Number");
            out.println("2 Search");
            out.println("3 Lookup Book");
            out.println("4 Exit");
            out.println("Enter Your Choice:");

            char choice = console.readLine().charAt(0);

            switch (choice) {

                case '1':
                    out.println("Enter Name: ");
                    name = console.readLine();

                    name = (name.equals("")) ? "Unknown name" : name;

                    out.println("Enter Phone Number: ");
                    num = console.readLine();

                    int length = num.length();
                    if (length < NUMBER_LENGTH || length > NUMBER_LENGTH) {
                        throw new IllegalArgumentException("Number Must be " + NUMBER_LENGTH + " Digits Long");
                    }

                    Phno = new Long(num);
                    //Add Name and Numbers
                    m.put(name, Phno);
                    break;

                case '2':
                    out.println("Enter Name :");
                    name = console.readLine();
                    name = name.trim();
                    Phno = m.get(name);

                    if (Phno == null) {
                        System.err.println("No Entry Found please add One");
                    } else {
                        out.println(Phno);
                    }
                    break;

                case '3':
                    m.entrySet().stream().forEach((en) -> {
                        Object Name = en.getKey();
                        Object no = en.getValue();
                        System.out.printf("Name = %s and No = %s\n", Name, no);
                    });
                    break;
                case '4':
                    return;
            }//switch end
        }//loop end
    }//main end

}