お手本のコードの中で意味がわからないところがあります。
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解決したいこと
お手本のコードで意味がわからないところがあります。
教えていただけないでしょうか？
このコードは
MobilePhone,
Contact,
Main
三つのクラスから構成されています。そして、ここではArrayListの学習をしているので、MobilePhoneでは、ContactクラスのArrayListを持っています。
ターミナルからインプットしてコンタクトを作ったり、足したり、編集したりする内容となっています。
Mainクラスで定義されている addNewContact() が疑問です。
この中に
Contact newContact = Contact.createContact(name, phone);
というコードがあるのですが、Contactというインスタンスを作った覚えがありません。
また、createContact（）メソッドはstaticメソッドなので、インスタンスを必要としません。
となると、Contactは何者なのでしょうか？
該当するソースコード MobilePhoneクラス
package com.timbuchalka;
import java.util.ArrayList;
/**
* Created by dev on 28/08/15.
*/
public class MobilePhone {
private String myNumber;
private ArrayList<Contact> myContacts;
public MobilePhone(String myNumber) {
this.myNumber = myNumber;
this.myContacts = new ArrayList<Contact>();
}
public boolean addNewContact(Contact contact) {
if(findContact(contact.getName()) >=0) {
System.out.println("Contact is already on file");
return false;
}
myContacts.add(contact);
return true;
}
public boolean updateContact(Contact oldContact, Contact newContact) {
int foundPosition = findContact(oldContact);
if(foundPosition <0) {
System.out.println(oldContact.getName() +", was not found.");
return false;
}
this.myContacts.set(foundPosition, newContact);
System.out.println(oldContact.getName() + ", was replaced with " + newContact.getName());
return true;
}
public boolean removeContact(Contact contact) {
int foundPosition = findContact(contact);
if(foundPosition <0) {
System.out.println(contact.getName() +", was not found.");
return false;
}
this.myContacts.remove(foundPosition);
System.out.println(contact.getName() + ", was deleted.");
return true;
}
private int findContact(Contact contact) {
return this.myContacts.indexOf(contact);
}
private int findContact(String contactName) {
for(int i=0; i<this.myContacts.size(); i++) {
Contact contact = this.myContacts.get(i);
if(contact.getName().equals(contactName)) {
return i;
}
}
return -1;
}
public String queryContact(Contact contact) {
if(findContact(contact) >=0) {
return contact.getName();
}
return null;
}
public Contact queryContact(String name) {
int position = findContact(name);
if(position >=0) {
return this.myContacts.get(position);
}
return null;
}
public void printContacts() {
System.out.println("Contact List");
for(int i=0; i<this.myContacts.size(); i++) {
System.out.println((i+1) + "." +
this.myContacts.get(i).getName() + " -> " +
this.myContacts.get(i).getPhoneNumber());
}
}
}
該当するソースコード Contact クラス
package com.timbuchalka;
/**
* Created by dev on 28/08/15.
*/
public class Contact {
private String name;
private String phoneNumber;
public Contact(String name, String phoneNumber) {
this.name = name;
this.phoneNumber = phoneNumber;
}
public String getName() {
return name;
}
public String getPhoneNumber() {
return phoneNumber;
}
public static Contact createContact(String name, String phoneNumber) {
return new Contact(name, phoneNumber);
}
}
該当するソースコード Mainクラス
package com.timbuchalka;
import java.util.Scanner;
public class Main {
private static Scanner scanner = new Scanner(System.in);
private static MobilePhone mobilePhone = new MobilePhone("0039 330 4404");
public static void main(String[] args) {
// Create a program that implements a simple mobile phone with the following capabilities.
// Able to store, modify, remove and query contact names.
// You will want to create a separate class for Contacts (name and phone number).
// Create a master class (MobilePhone) that holds the ArrayList of Contacts
// The MobilePhone class has the functionality listed above.
// Add a menu of options that are available.
// Options: Quit, print list of contacts, add new contact, update existing contact, remove contact
// and search/find contact.
// When adding or updating be sure to check if the contact already exists (use name)
// Be sure not to expose the inner workings of the Arraylist to MobilePhone
// e.g. no ints, no .get(i) etc
// MobilePhone should do everything with Contact objects only.
boolean quit = false;
startPhone();
printActions();
while(!quit) {
System.out.println("\nEnter action: (6 to show available actions)");
int action = scanner.nextInt();
scanner.nextLine();
switch (action) {
case 0:
System.out.println("\nShutting down...");
quit = true;
break;
case 1:
mobilePhone.printContacts();
break;
case 2:
addNewContact();
break;
case 3:
updateContact();
break;
case 4:
removeContact();
break;
case 5:
queryContact();
break;
case 6:
printActions();
break;
}
}
}
private static void addNewContact() {
System.out.println("Enter new contact name: ");
String name = scanner.nextLine();
System.out.println("Enter phone number: ");
String phone = scanner.nextLine();
Contact newContact = Contact.createContact(name, phone);
//↑インスタンス？
if(mobilePhone.addNewContact(newContact)) {
System.out.println("New contact added: name = " + name + ", phone = "+ phone);
} else {
System.out.println("Cannot add, " + name + " already on file");
}
}
private static void updateContact() {
System.out.println("Enter existing contact name: ");
String name = scanner.nextLine();
Contact existingContactRecord = mobilePhone.queryContact(name);
if(existingContactRecord == null) {
System.out.println("Contact not found.");
return;
}
System.out.print("Enter new contact name: ");
String newName = scanner.nextLine();
System.out.print("Enter new contact phone number: ");
String newNumber = scanner.nextLine();
Contact newContact = Contact.createContact(newName, newNumber);
if(mobilePhone.updateContact(existingContactRecord, newContact)) {
System.out.println("Successfully updated record");
} else {
System.out.println("Error updating record.");
}
}
private static void removeContact() {
System.out.println("Enter existing contact name: ");
String name = scanner.nextLine();
Contact existingContactRecord = mobilePhone.queryContact(name);
if (existingContactRecord == null) {
System.out.println("Contact not found.");
return;
}
if(mobilePhone.removeContact(existingContactRecord)) {
System.out.println("Successfully deleted");
} else {
System.out.println("Error deleting contact");
}
}
private static void queryContact() {
System.out.println("Enter existing contact name: ");
String name = scanner.nextLine();
Contact existingContactRecord = mobilePhone.queryContact(name);
if (existingContactRecord == null) {
System.out.println("Contact not found.");
return;
}
System.out.println("Name: " + existingContactRecord.getName() + " phone number is " + existingContactRecord.getPhoneNumber());
}
private static void startPhone() {
System.out.println("Starting phone...");
}
private static void printActions() {
System.out.println("\nAvailable actions:\npress");
System.out.println("0 - to shutdown\n" +
"1 - to print contacts\n" +
"2 - to add a new contact\n" +
"3 - to update existing an existing contact\n" +
"4 - to remove an existing contact\n" +
"5 - query if an existing contact exists\n" +
"6 - to print a list of available actions.");
System.out.println("Choose your action: ");
}
}
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