Model1 방식

package jbank;
import java.io.*;

public class AccountMain {
 public static void main(String[] ar) throws NumberFormatException, IOException {
  AccountManager jbank = new AccountManager();
 
  BufferedReader in = new BufferedReader (new InputStreamReader (System.in));
 
  while(true) {
   jbank.printMenu();
   
   System.out.print("선택: ");
   int choice = Integer.parseInt(in.readLine());
   
   switch (choice) {
    case 1: jbank.makeAccount(); break; // 계좌개설    
    case 2: jbank.inMoney(); break;  // 입금
    case 3: jbank.outMoney(); break; // 출금
    case 4: jbank.showMoney(); break; // 잔액조회
    case 5: System.out.println("감사합니다."); return;
    default: System.out.println("선택을 잘못하셨습니다.");
   }
  }
 }
}


==========================================================================================================================================

package jbank;
import java.io.*;

public class AccountManager {
 Account[] array = new Account[100];
 
 int index;
 
 BufferedReader in;
 
 public AccountManager() {
  index = 0;
 }
 
 public void printMenu() {
  System.out.println("====== Menu ======");
  System.out.println("1. 계좌개설");
  System.out.println("2. 입금");
  System.out.println("3. 출금");
  System.out.println("4. 잔액조회");
  System.out.println("5. 프로그램 종료");
  System.out.println("====== Bye ======");
 }
 
 public void makeAccount() throws IOException { //계좌개설하기
  in = new BufferedReader (new InputStreamReader (System.in));
 
  System.out.println("계좌개설 ====== ");
  System.out.println("계좌번호 : ");
  int id = Integer.parseInt(in.readLine());
 
  System.out.println("이름 : ");
  String name = in.readLine();
 
  System.out.println("입금액 : ");
  int balance = Integer.parseInt(in.readLine());
 
  array[index++] = new Account(id, balance, name);
 }
 
 public void inMoney() throws IOException { //입금하기
  in = new BufferedReader (new InputStreamReader (System.in));
 
  System.out.print("계좌 ID : ");
  int id = Integer.parseInt(in.readLine());
 
  System.out.println("입금액 : ");
  int money = Integer.parseInt(in.readLine());
 
  for (int i = 0; i < index; i++) {
   if(array[i].getId() == id) {
    array[i].addMoney(money);
    System.out.println("입금완료!!!");
    return;
   }
  }
  System.out.println("유효하지 않은 ID 입니다.");
 }
 
 public void outMoney() throws IOException { //출금하기
  in = new BufferedReader (new InputStreamReader (System.in));
 
  System.out.print("계좌 ID : ");
  int id = Integer.parseInt(in.readLine());
 
  System.out.println("출금액 : ");
  int money = Integer.parseInt(in.readLine());
 
  for (int i = 0; i < index; i++) {
   if(array[i].getId() == id) {
    if(array[i].getBalance() < money) {
     System.out.println("잔액부족");
     return;
    }
   
    array[i].minMoney(money);
    System.out.println("출금완료!!!");
    return;
   }
  }
  System.out.println("유효하지 않은 ID 입니다.");
 }
 
 public void showMoney() throws IOException { //잔액조회
  in = new BufferedReader (new InputStreamReader (System.in));
 
  System.out.print("계좌 ID : ");
  int id = Integer.parseInt(in.readLine());
 
  for(int i = 0; i < index; i++) {
   if(array[i].getId() == id) {
    array[i].showData();
   }
  }
 }
}

==========================================================================================================================================

package jbank;

public class Account {
 private int id; //계좌번호
 private int balance; //잔액
 private String name; //이름
 
 public Account(int id, int balance, String name) { //생성자
  this.id = id;
  this.balance = balance;
  this.name = name;
 }
 
 public int getId() {
  return id;
 }
 
 public int getBalance() {
  return balance;
 }
 
 public void addMoney(int value) { //입금
  balance += value;
 }
 
 public void minMoney(int value) { //출금
  balance -= value;
 }
 
 public void showData() { //계좌정보 보여주기
  System.out.println("계좌번호 : " + id);
  System.out.println("이름  : " + name);
  System.out.println("잔액  : " + balance);
 }
}