diff --git a/src/me/smartstore/Main.java b/src/me/smartstore/Main.java
new file mode 100644
index 00000000..ba2d4eae
--- /dev/null
+++ b/src/me/smartstore/Main.java
@@ -0,0 +1,8 @@
+package me.smartstore;
+
+public class Main {
+    public static void main(String[] args) {
+        SmartStoreApp.getInstance().run();
+    }
+}
+
diff --git a/src/me/smartstore/SmartStoreApp.java b/src/me/smartstore/SmartStoreApp.java
new file mode 100644
index 00000000..5a826143
--- /dev/null
+++ b/src/me/smartstore/SmartStoreApp.java
@@ -0,0 +1,43 @@
+package me.smartstore;
+
+import me.smartstore.customer.Customer;
+import me.smartstore.customer.Customers;
+import me.smartstore.group.Group;
+import me.smartstore.group.GroupType;
+import me.smartstore.group.Groups;
+import me.smartstore.group.Parameter;
+import me.smartstore.menu.*;
+
+public class SmartStoreApp {
+    private final Groups allGroups = Groups.getInstance();
+    private final Customers allCustomers = Customers.getInstance();
+
+    private final MainMenu mainMenu = MainMenu.getInstance();
+
+    // singleton
+    private static SmartStoreApp smartStoreApp;
+
+    public static SmartStoreApp getInstance() {
+        if (smartStoreApp == null) {
+            smartStoreApp = new SmartStoreApp();
+        }
+        return smartStoreApp;
+    }
+
+    private SmartStoreApp() {}
+
+    public void details() {
+        System.out.println("\n\n===========================================");
+        System.out.println(" Title : SmartStore Customer Classification");
+        System.out.println(" Release Date : 23.05.15");
+        System.out.println(" Copyright 2023 HaesolChoi All rights reserved.");
+        System.out.println("===========================================\n");
+    }
+
+
+    public void run() {
+        details();
+        mainMenu.manage();
+
+    }
+}
diff --git a/src/me/smartstore/arrays/Collections.java b/src/me/smartstore/arrays/Collections.java
new file mode 100644
index 00000000..536be0a1
--- /dev/null
+++ b/src/me/smartstore/arrays/Collections.java
@@ -0,0 +1,16 @@
+package me.smartstore.arrays;
+
+public interface Collections<T> {
+    // 데이터를 가지고 있는 객체가 아님
+    // 구현 해야하는 메소드의 정보만 가지고 있음 (인터페이스)
+
+    int size();
+    T get(int index);
+    void set(int index, T object);
+    int indexOf(T object);
+    void add(T object);
+    void add(int index, T object);
+    T pop();
+    T pop(int index);
+    T pop(T object);
+}
\ No newline at end of file
diff --git a/src/me/smartstore/arrays/DArray.java b/src/me/smartstore/arrays/DArray.java
new file mode 100644
index 00000000..d6ab7f1b
--- /dev/null
+++ b/src/me/smartstore/arrays/DArray.java
@@ -0,0 +1,155 @@
+package me.smartstore.arrays;
+
+import me.smartstore.exception.EmptyArrayException;
+import me.smartstore.exception.ElementNotFoundException;
+import me.smartstore.exception.NullArgumentException;
+
+public class DArray<T> implements Collections<T> { // Dynamic Array
+
+    protected static final int DEFAULT = 10;
+
+    protected T[] arrays;
+    protected int size;
+    protected int capacity;
+
+    @SuppressWarnings("unchecked")
+    public DArray() {
+        arrays = (T[]) new Object[DEFAULT];
+        capacity = DEFAULT;
+    }
+
+    @SuppressWarnings("unchecked")
+    public DArray(int initial) {
+        arrays = (T[]) new Object[initial];
+        capacity = initial;
+    }
+
+    public DArray(T[] arrays) {
+        this.arrays = arrays;
+        capacity = arrays.length;
+        size = arrays.length;
+    }
+
+    /////////////////////////////////////////
+    // add, set, get, pop, indexOf, size, capacity (for dynamic-sized array)
+
+    @Override
+    public int size() {
+        return size;
+    }
+
+    // 배열에 얼마나 capacity 남아있는지 외부에 알려줄 필요가 없기 때문에 <protected>으로 정의
+    protected int capacity() {
+        return capacity;
+    }
+
+    @Override
+    public T get(int index) throws IndexOutOfBoundsException {
+        if (index < 0 || index >= size) throw new IndexOutOfBoundsException();
+        return arrays[index];
+    }
+
+    /**
+     * @param: ...
+     * @return: ...
+     * @throws: IndexOutOfBoundsException
+     * @throws: NullArgumentException
+     * */
+    @Override
+    public void set(int index, T object) throws IndexOutOfBoundsException, NullArgumentException {
+        if (index < 0 || index >= size) throw new IndexOutOfBoundsException();
+        if (object == null) throw new NullArgumentException();
+
+        arrays[index] = object;
+    }
+
+    @Override
+    public int indexOf(T object) throws NullArgumentException, ElementNotFoundException {
+        if (object == null) throw new NullArgumentException(); // not found (instead of throwing exception)
+
+        for (int i = 0; i < size; i++) {
+            if (arrays[i] == null) continue;
+            if (arrays[i].equals(object)) return i;
+        }
+        throw new ElementNotFoundException(); // not found
+    }
+
+    // 배열의 cap이 부족한 경우
+    @Override
+    public void add(T object) throws NullArgumentException {
+        if (object == null) throw new NullArgumentException(); // if argument is null, do not add null value in array
+
+        if (size < capacity) {
+            arrays[size] = object;
+            size++;
+        } else {
+            grow();
+            add(object);
+        }
+    }
+
+    @Override
+    public void add(int index, T object) throws IndexOutOfBoundsException, NullArgumentException {
+        if (index < 0 || index >= size) throw new IndexOutOfBoundsException();
+        if (object == null) throw new NullArgumentException();
+
+        if (size < capacity) {
+            for (int i = size-1; i >= index ; i--) {
+                arrays[i+1] = arrays[i];
+            }
+            arrays[index] = object;
+            size++;
+        } else {
+            grow();
+            add(index, object);
+        }
+    }
+
+    @Override
+    public T pop() {
+//        if (size == 0) return null;
+//
+//        T popElement = arrays[size-1];
+//        arrays[size-1] = null;
+//        size--;
+//        return popElement;
+        return pop(size-1);
+    }
+
+    @Override
+    public T pop(int index) throws IndexOutOfBoundsException {
+        if (size == 0) throw new EmptyArrayException();
+        if (index < 0 || index >= size) throw new IndexOutOfBoundsException();
+
+        T popElement = arrays[index];
+        arrays[index] = null; // 삭제됨을 명시적으로 표현
+
+        for (int i = index+1; i < size; i++) {
+            arrays[i-1] = arrays[i];
+        }
+        arrays[size-1] = null;
+        size--;
+        return popElement;
+    }
+
+    @Override
+    public T pop(T object) {
+        return pop(indexOf(object));
+    }
+
+    protected void grow() {
+        capacity *= 2; // doubling
+        arrays = java.util.Arrays.copyOf(arrays, capacity);
+
+        // size는 그대로
+    }
+
+    @Override
+    public String toString() {
+        String toStr = "";
+        for (int i = 0; i < size; i++) {
+            toStr += (arrays[i] + "\n");
+        }
+        return toStr;
+    }
+}
diff --git a/src/me/smartstore/customer/Customer.java b/src/me/smartstore/customer/Customer.java
new file mode 100644
index 00000000..de67f96d
--- /dev/null
+++ b/src/me/smartstore/customer/Customer.java
@@ -0,0 +1,96 @@
+package me.smartstore.customer;
+
+import me.smartstore.group.Group;
+import java.util.Objects;
+
+
+public class Customer implements Comparable<Customer> {
+    private String userId;
+    private String name;
+    private Integer spentTime;
+    private Integer totalPay;
+    private Group group;
+
+    public Customer() {
+    }
+
+    public Customer(String name, String userId, int spentTime, int totalPay) {
+        this.name = name;
+        this.userId = userId;
+        this.spentTime = Integer.valueOf(spentTime);
+        this.totalPay = Integer.valueOf(totalPay);
+    }
+
+    public String getName() {
+        return this.name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    public String getUserId() {
+        return this.userId;
+    }
+
+    public void setUserId(String userId) {
+        this.userId = userId;
+    }
+
+    public Integer getSpentTime() {
+        return this.spentTime;
+    }
+
+    public void setSpentTime(Integer spentTime) {
+        this.spentTime = spentTime;
+    }
+
+    public Integer getTotalPay() {
+        return this.totalPay;
+    }
+
+    public void setTotalPay(Integer totalPay) {
+        this.totalPay = totalPay;
+    }
+
+    public Group getGroup() {
+        return this.group;
+    }
+
+    public void setGroup(Group group) {
+        this.group = group;
+    }
+
+    @Override
+    public int compareTo(Customer o) {
+        if (this.name.compareTo(o.name) < 0)
+            return -1;
+        if (this.name.compareTo(o.name) == 0)
+            return this.userId.compareTo(o.userId);
+        return 1;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) {return true;}
+        if (o == null || getClass() != o.getClass()) {return false;}
+        Customer customer = (Customer) o;
+        return Objects.equals(userId, customer.userId);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(userId);
+    }
+
+    @Override
+    public String toString() {
+        return "Customer{" +
+                "userId='" + userId + '\'' +
+                ", name='" + name + '\'' +
+                ", spentTime=" + spentTime +
+                ", totalPay=" + totalPay +
+                ", group=" + group +
+                '}';
+    }
+}
diff --git a/src/me/smartstore/customer/Customers.java b/src/me/smartstore/customer/Customers.java
new file mode 100644
index 00000000..eee93cdf
--- /dev/null
+++ b/src/me/smartstore/customer/Customers.java
@@ -0,0 +1,97 @@
+package me.smartstore.customer;
+
+import me.smartstore.arrays.DArray;
+import me.smartstore.group.GroupType;
+import me.smartstore.group.Groups;
+import me.smartstore.group.Group;
+import me.smartstore.group.Parameter;
+import me.smartstore.customer.Customer;
+import me.smartstore.util.Util;
+
+
+import static me.smartstore.group.Groups.allGroups;
+
+public class Customers extends DArray<Customer> {
+
+    // singleton
+    private static Customers allCustomers;
+
+    public static Customers getInstance() {
+        if (allCustomers == null) {
+            allCustomers = new Customers();
+        }
+        return allCustomers;
+    }
+
+    private final Groups allGroups = Groups.getInstance();
+
+    private Customers() {}
+
+    public void setCustomers(Customer[] customers) {
+        this.arrays = customers;
+        capacity = customers.length;
+        size = customers.length;
+    }
+
+    public Customer[] getCustomers() {
+        return arrays;
+    }
+
+
+    public Customers findCustomers(GroupType type) {
+        Customers custs = new Customers();
+
+        for(int i = 0; i < size; ++i) {
+            Customer cust = get(i);
+            if (cust == null) return null;
+
+            Group grp = cust.getGroup();
+            if (type == GroupType.NONE) { // Customer Group == null =>
+                if (grp == null || grp.getGroupType() == null || grp.getGroupType() == GroupType.NONE) {
+                    custs.add(cust);
+                }
+            } else if (grp != null && grp.getGroupType() == type) {
+                custs.add(cust);
+            }
+
+        }
+
+        return custs;
+    }
+
+    public Customers findCustomers(Group grp) {
+        if (grp != null) {
+            if (grp.getGroupType() != null) {
+                return findCustomers(grp.getGroupType());
+            } else {
+                System.out.println("Customers.findCustomers() Error : No group type.");
+                return null;
+            }
+        } else {
+            System.out.println("Customers.findCustomers() Error : No group.");
+            return null;
+        }
+    }
+
+    // refresh 함수가 호출되는 경우
+    // 1. 분류기준 바뀔 때
+    // 2. 새로운 고객이 들어올 때
+    public void refresh(Groups groups) {
+        if (groups == null) return;
+
+        for (int i = 0; i < size; i++) {
+            Customer cust = arrays[i];
+            Group grp = findGroupFor(cust);
+            if (grp == null) {
+                grp = groups.find(GroupType.NONE);
+            }
+            cust.setGroup(grp);
+        }
+
+    }
+
+    public Group findGroupFor(Customer cust) {
+        return cust.getGroup();
+    }
+
+}
diff --git a/src/me/smartstore/exception/ArrayEmptyException.java b/src/me/smartstore/exception/ArrayEmptyException.java
new file mode 100644
index 00000000..13cf8787
--- /dev/null
+++ b/src/me/smartstore/exception/ArrayEmptyException.java
@@ -0,0 +1,14 @@
+package me.smartstore.exception;
+
+import me.smartstore.util.Message;
+
+public class ArrayEmptyException extends RuntimeException {
+
+    public ArrayEmptyException() {
+        super(Message.ERR_MSG_INVALID_ARR_EMPTY.getMessage());
+    }
+
+    public ArrayEmptyException(String message) {
+        super(message);
+    }
+}
diff --git a/src/me/smartstore/exception/ElementNotFoundException.java b/src/me/smartstore/exception/ElementNotFoundException.java
new file mode 100644
index 00000000..b72cbc84
--- /dev/null
+++ b/src/me/smartstore/exception/ElementNotFoundException.java
@@ -0,0 +1,10 @@
+package me.smartstore.exception;
+
+public class ElementNotFoundException extends RuntimeException {
+    public ElementNotFoundException() {
+    }
+
+    public ElementNotFoundException(String message) {
+        super(message);
+    }
+}
\ No newline at end of file
diff --git a/src/me/smartstore/exception/EmptyArrayException.java b/src/me/smartstore/exception/EmptyArrayException.java
new file mode 100644
index 00000000..812bb15d
--- /dev/null
+++ b/src/me/smartstore/exception/EmptyArrayException.java
@@ -0,0 +1,10 @@
+package me.smartstore.exception;
+
+public class EmptyArrayException extends RuntimeException {
+    public EmptyArrayException() {
+    }
+
+    public EmptyArrayException(String message) {
+        super(message);
+    }
+}
diff --git a/src/me/smartstore/exception/InputEmptyException.java b/src/me/smartstore/exception/InputEmptyException.java
new file mode 100644
index 00000000..58861400
--- /dev/null
+++ b/src/me/smartstore/exception/InputEmptyException.java
@@ -0,0 +1,14 @@
+package me.smartstore.exception;
+
+import me.smartstore.util.Message;
+
+public class InputEmptyException extends RuntimeException {
+
+    public InputEmptyException() {
+        super(Message.ERR_MSG_INVALID_INPUT_EMPTY.getMessage());
+    }
+
+    public InputEmptyException(String message) {
+        super(message);
+    }
+}
\ No newline at end of file
diff --git a/src/me/smartstore/exception/InputEndException.java b/src/me/smartstore/exception/InputEndException.java
new file mode 100644
index 00000000..68611dec
--- /dev/null
+++ b/src/me/smartstore/exception/InputEndException.java
@@ -0,0 +1,13 @@
+package me.smartstore.exception;
+
+import me.smartstore.util.Message;
+
+public class InputEndException extends RuntimeException {
+    public InputEndException() {
+        super(Message.ERR_MSG_INPUT_END.getMessage());
+    }
+
+    public InputEndException(String message) {
+        super(message);
+    }
+}
diff --git a/src/me/smartstore/exception/InputFormatException.java b/src/me/smartstore/exception/InputFormatException.java
new file mode 100644
index 00000000..1ca8e589
--- /dev/null
+++ b/src/me/smartstore/exception/InputFormatException.java
@@ -0,0 +1,13 @@
+package me.smartstore.exception;
+
+import me.smartstore.util.Message;
+
+public class InputFormatException extends RuntimeException {
+    public InputFormatException() {
+        super(Message.ERR_MSG_INVALID_INPUT_FORMAT.getMessage());
+    }
+
+    public InputFormatException(String message) {
+        super(message);
+    }
+}
diff --git a/src/me/smartstore/exception/InputRangeException.java b/src/me/smartstore/exception/InputRangeException.java
new file mode 100644
index 00000000..739fe8f1
--- /dev/null
+++ b/src/me/smartstore/exception/InputRangeException.java
@@ -0,0 +1,13 @@
+package me.smartstore.exception;
+
+import me.smartstore.util.Message;
+
+public class InputRangeException extends RuntimeException {
+    public InputRangeException() {
+        super(Message.ERR_MSG_INVALID_INPUT_RANGE.getMessage());
+    }
+
+    public InputRangeException(String message) {
+        super(message);
+    }
+}
diff --git a/src/me/smartstore/exception/InputTypeException.java b/src/me/smartstore/exception/InputTypeException.java
new file mode 100644
index 00000000..ff1d543b
--- /dev/null
+++ b/src/me/smartstore/exception/InputTypeException.java
@@ -0,0 +1,13 @@
+package me.smartstore.exception;
+
+import me.smartstore.util.Message;
+
+public class InputTypeException extends RuntimeException {
+    public InputTypeException() {
+        super(Message.ERR_MSG_INVALID_INPUT_TYPE.getMessage());
+    }
+
+    public InputTypeException(String message) {
+        super(message);
+    }
+}
\ No newline at end of file
diff --git a/src/me/smartstore/exception/NullArgumentException.java b/src/me/smartstore/exception/NullArgumentException.java
new file mode 100644
index 00000000..e8b87b1d
--- /dev/null
+++ b/src/me/smartstore/exception/NullArgumentException.java
@@ -0,0 +1,10 @@
+package me.smartstore.exception;
+
+public class NullArgumentException extends RuntimeException {
+    public NullArgumentException() {
+    }
+
+    public NullArgumentException(String message) {
+        super(message);
+    }
+}
\ No newline at end of file
diff --git a/src/me/smartstore/group/Group.java b/src/me/smartstore/group/Group.java
new file mode 100644
index 00000000..a27bcafd
--- /dev/null
+++ b/src/me/smartstore/group/Group.java
@@ -0,0 +1,70 @@
+package me.smartstore.group;
+
+import me.smartstore.customer.Customers;
+import me.smartstore.group.GroupType;
+import me.smartstore.group.Parameter;
+
+import java.util.Objects;
+
+public class Group {
+    private GroupType groupType;
+    private Parameter parameter;
+
+    public Group() {
+        this(null, null);
+    }
+
+    public Group(GroupType groupType, Parameter parameter) {
+        this.groupType = groupType;
+        this.parameter = parameter;
+    }
+
+    public GroupType getGroupType() {
+        return groupType;
+    }
+
+    public void getGroupType(GroupType groupType) {
+        this.groupType = groupType;
+    }
+
+    public Parameter getParameter() {
+        return parameter;
+    }
+
+    public void setParameter(Parameter param) {
+        this.parameter = param;
+    }
+
+    public Customers getCustomers(Customers allCustomers) {
+        return allCustomers.findCustomers(this.getGroupType());
+    }
+
+    public void update(GroupType groupType, Parameter parameter) {
+        this.groupType = groupType;
+        this.parameter = parameter;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) return true;
+        if (o == null || getClass() != o.getClass()) return false;
+        Group group = (Group) o;
+        return groupType == group.groupType && Objects.equals(parameter, group.parameter);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(groupType, parameter);
+    }
+
+    @Override
+    public String toString() {
+        if (groupType == null) {
+            return "No group.";
+        } else if (parameter == null) {
+            return "GroupType: " + groupType + "\nParameter: null";
+        } else {
+            return "GroupType: " + groupType + "\nParameter: " + parameter;
+        }
+    }
+}
\ No newline at end of file
diff --git a/src/me/smartstore/group/GroupType.java b/src/me/smartstore/group/GroupType.java
new file mode 100644
index 00000000..d6ccca37
--- /dev/null
+++ b/src/me/smartstore/group/GroupType.java
@@ -0,0 +1,22 @@
+package me.smartstore.group;
+
+public enum GroupType {
+    NONE("해당없음"), GENERAL("일반고객"), VIP("우수고객"), VVIP("최우수고객"),
+    N("해당없음"), G("일반고객"), V("우수고객"), VV("최우수고객");
+
+
+    String groupType = "";
+
+
+    GroupType(String groupType) {
+        this.groupType = groupType;
+    }
+
+    public GroupType replaceFullName() {
+        if (this == N) return NONE;
+        else if (this == G) return GENERAL;
+        else if (this == V) return VIP;
+        else if (this == VV) return VVIP;
+        return this;
+    }
+}
diff --git a/src/me/smartstore/group/Groups.java b/src/me/smartstore/group/Groups.java
new file mode 100644
index 00000000..6a0c9f98
--- /dev/null
+++ b/src/me/smartstore/group/Groups.java
@@ -0,0 +1,36 @@
+package me.smartstore.group;
+
+import me.smartstore.arrays.DArray;
+
+public class Groups extends DArray<Group> {
+    // singleton
+    public static Groups allGroups;
+
+    public static Groups getInstance() {
+        if (allGroups == null) {
+            allGroups = new Groups();
+        }
+        return allGroups;
+    }
+
+    private Groups() {
+    }
+
+    public Group find(GroupType groupType) {
+        for (int i = 0; i < allGroups.size(); i++) {
+            Group group = allGroups.get(i);
+            if (group.getGroupType() == groupType) {
+                return group;
+            }
+        }
+        return null;
+    }
+
+    public void update(Group group) {
+        Group grp = find(group.getGroupType());
+        if (grp != null) {
+            grp.setParameter(group.getParameter());
+        }
+
+    }
+}
diff --git a/src/me/smartstore/group/Parameter.java b/src/me/smartstore/group/Parameter.java
new file mode 100644
index 00000000..9b711f41
--- /dev/null
+++ b/src/me/smartstore/group/Parameter.java
@@ -0,0 +1,54 @@
+package me.smartstore.group;
+
+import java.util.Objects;
+
+public class Parameter {
+    private Integer minTime;
+    private Integer minPay;
+
+
+    public Parameter() {
+    }
+
+    public Parameter(Integer minTime, Integer minPay) {
+        this.minTime = minTime;
+        this.minPay = minPay;
+    }
+
+    public Integer getMinTime() {
+        return minTime;
+    }
+
+    public void setMinTime(Integer minTime) {
+        this.minTime = minTime;
+    }
+
+    public Integer getMinPay() {
+        return minPay;
+    }
+
+    public void setMinPay(Integer minPay) {
+        this.minPay = minPay;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) return true;
+        if (o == null || getClass() != o.getClass()) return false;
+        Parameter parameter = (Parameter) o;
+        return Objects.equals(minTime, parameter.minTime) && Objects.equals(minPay, parameter.minPay);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(minTime, minPay);
+    }
+
+    @Override
+    public String toString() {
+        return "Parameter{" +
+                "minTime=" + minTime +
+                ", minPay=" + minPay +
+                '}';
+    }
+}
diff --git a/src/me/smartstore/menu/CustomerMenu.java b/src/me/smartstore/menu/CustomerMenu.java
new file mode 100644
index 00000000..0c86da91
--- /dev/null
+++ b/src/me/smartstore/menu/CustomerMenu.java
@@ -0,0 +1,27 @@
+package me.smartstore.menu;
+
+public class CustomerMenu implements Menu {
+    // singleton
+    private static CustomerMenu customerMenu;
+
+    public static CustomerMenu getInstance() {
+        if (customerMenu == null) {
+            customerMenu = new CustomerMenu();
+        }
+        return customerMenu;
+    }
+
+    private CustomerMenu() {}
+
+    @Override
+    public void manage() {
+        while ( true ) { // 서브 메뉴 페이지를 유지하기 위한 while
+            int choice = chooseMenu(new String[]{
+                    "Add Customer",
+                    "View Customer",
+                    "Update Customer",
+                    "Delete Customer",
+                    "Back"});
+        }
+    }
+}
diff --git a/src/me/smartstore/menu/GroupMenu.java b/src/me/smartstore/menu/GroupMenu.java
new file mode 100644
index 00000000..1016a072
--- /dev/null
+++ b/src/me/smartstore/menu/GroupMenu.java
@@ -0,0 +1,223 @@
+package me.smartstore.menu;
+
+import me.smartstore.customer.Customers;
+import me.smartstore.exception.InputEmptyException;
+import me.smartstore.exception.InputEndException;
+import me.smartstore.exception.InputFormatException;
+import me.smartstore.exception.InputRangeException;
+import me.smartstore.group.Group;
+import me.smartstore.group.GroupType;
+import me.smartstore.group.Groups;
+import me.smartstore.group.Parameter;
+import me.smartstore.util.Message;
+import me.smartstore.util.Util;
+
+public class GroupMenu implements Menu {
+
+    /////////////////////////////////////////
+    ////////////// singleton ////////////////
+    private static GroupMenu groupMenu;
+
+    public static GroupMenu getInstance() {
+        if (groupMenu == null) {
+            groupMenu = new GroupMenu();
+        }
+        return groupMenu;
+    }
+    /////////////////////////////////////////
+    /////////////////////////////////////////
+
+
+    Groups allGroups = Groups.getInstance();
+    Customers allCustomers = Customers.getInstance();
+
+
+    public String chooseGroup() {
+        while ( true ) {
+            try {
+                System.out.print("Which group (GENERAL (G), VIP (V), VVIP (VV))? ");
+                String choice = nextLine(Message.END_MSG);
+
+                if (choice.equals("")) throw new InputEmptyException();
+                return choice;
+
+            } catch (InputEmptyException e) {
+                System.out.println(Message.ERR_MSG_INVALID_INPUT_NULL);
+            } catch (IllegalArgumentException e) {
+                System.out.println(Message.ERR_MSG_INVALID_INPUT_RANGE);
+            } catch (InputEndException e) {
+                System.out.println(Message.ERR_MSG_INPUT_END);
+                return null;
+            }
+        }
+    }
+
+    @Override
+    public void manage() {
+        while ( true ) {
+            int choice = chooseMenu(new String[]{
+                    "Set Parameter",
+                    "View Parameter",
+                    "Update Parameter",
+                    "Back"});
+
+            if (choice == 1) {
+                setParameter();
+            } else if (choice == 2) {
+                viewParameter();
+            } else if (choice == 3) {
+                updateParameter();
+            } else if (choice == 4) {
+                break;
+            }
+        }
+    }
+
+    public void setParameter() {
+        while ( true ) {
+            String strGroup = chooseGroup(); // "V", "VIP" (string) => GroupType.VIP
+            if (strGroup == null) return;
+
+            GroupType groupType;
+            try {
+                groupType = GroupType.valueOf(strGroup).replaceFullName();
+            } catch (IllegalArgumentException e) {
+                System.out.println("\n" + Message.ERR_MSG_INVALID_INPUT_RANGE);
+                continue;
+            }
+
+            Group grp = allGroups.find(groupType);
+            if (grp != null && grp.getParameter() != null) {
+                System.out.println("\n" + grp.getGroupType() + " group already exists.");
+                System.out.println("\n" + grp);
+            } else {
+                Parameter param = new Parameter();
+
+                while ( true ) {
+                    int choice = chooseMenu(new String[]{
+                            "Minimum Spent Time",
+                            "Minimum Total Pay",
+                            "Back"});
+                    if (choice == 1) {
+                        setParameterMinimumSpentTime(param);
+                    } else if (choice == 2) {
+                        setParameterMinimumTotalPay(param);
+                    } else if (choice == 3) break;
+//                    else System.out.println("\n" + Message.ERR_MSG_INVALID_INPUT_RANGE);
+                }
+
+                if (Util.isAllNonNUll(param, param.getMinTime(), param.getMinPay())) {
+                    Group newGrp = allGroups.find(groupType);
+                    newGrp.setParameter(param);
+                    allCustomers.refresh(allGroups);
+                    System.out.println("\n" + newGrp);
+                } else {
+                    System.out.println("No parameter is added. Please fill out all information.");
+                }
+            }
+        }
+    }
+
+    public void viewParameter() {
+        while ( true ) {
+            String strGroup = chooseGroup();
+            if (strGroup == null) return;
+
+            GroupType groupType;
+            try {
+                groupType = GroupType.valueOf(strGroup).replaceFullName();
+            } catch (IllegalArgumentException e) {
+                System.out.println("\n" + Message.ERR_MSG_INVALID_INPUT_TYPE);
+                continue;
+            }
+
+            Group grp = allGroups.find(groupType);
+            System.out.println();
+            System.out.println(grp);
+        }
+    }
+
+    public void updateParameter() {
+        while ( true ) {
+            String strGroup = chooseGroup();
+            if (strGroup == null) return;
+
+            GroupType groupType;
+            try {
+                groupType = GroupType.valueOf(strGroup).replaceFullName();
+            } catch (IllegalArgumentException e) {
+                System.out.println("\n" + Message.ERR_MSG_INVALID_INPUT_RANGE);
+                return;
+            }
+
+            Group grp = allGroups.find(groupType);
+            if (grp == null || grp.getParameter() == null) {
+                System.out.println("\nNo parameter. Set the parameter first.");
+                return;
+            }
+
+            System.out.println("\n" + grp);
+            Parameter param = grp.getParameter();
+
+            while ( true ) {
+                int choice = chooseMenu(new String[]{
+                        "Minimum Spent Time",
+                        "Minimum Total Pay",
+                        "Back"});
+                if (choice == 1) {
+                    setParameterMinimumSpentTime(param);
+                } else if (choice == 2) {
+                    setParameterMinimumTotalPay(param);
+                } else if (choice == 3) {
+                    break;
+                }
+            }
+
+            allGroups.update(new Group(groupType, param));
+            allCustomers.refresh(allGroups);
+            System.out.println("\n" + grp);
+
+        }
+    }
+
+    public void setParameterMinimumSpentTime(Parameter param) {
+        while ( true ) {
+            try {
+                System.out.print("\nInput Minimum Spent Time: ");
+                int minimumSpentTime = Integer.parseInt(nextLine(Message.END_MSG));
+                if (minimumSpentTime < 0) throw new InputRangeException();
+
+                param.setMinTime(minimumSpentTime);
+                return;
+            } catch (InputFormatException e) {
+                System.out.println(Message.ERR_MSG_INVALID_INPUT_TYPE);
+            } catch (InputRangeException e) {
+                System.out.println(Message.ERR_MSG_INVALID_INPUT_RANGE);
+            } catch (InputEndException e) {
+                System.out.println(Message.ERR_MSG_INPUT_END);
+                return;
+            }
+        }
+    }
+
+
+    public void setParameterMinimumTotalPay(Parameter param) {
+
+        while ( true ) {
+            try {
+                System.out.print("\nInput Minimum Total Pay: ");
+                int minimumTotalPay = Integer.parseInt(nextLine(Message.END_MSG));
+                if (minimumTotalPay < 0) throw new InputRangeException();
+                param.setMinPay(minimumTotalPay);
+                return;
+            } catch (InputFormatException e) {
+                System.out.println(Message.ERR_MSG_INVALID_INPUT_TYPE);
+            } catch (InputRangeException e) {
+                System.out.println(Message.ERR_MSG_INVALID_INPUT_RANGE);
+            } catch (InputEndException e) {
+                System.out.println(Message.ERR_MSG_INPUT_END);
+                return;
+            }
+        }
+    }
+}
diff --git a/src/me/smartstore/menu/MainMenu.java b/src/me/smartstore/menu/MainMenu.java
new file mode 100644
index 00000000..a7768657
--- /dev/null
+++ b/src/me/smartstore/menu/MainMenu.java
@@ -0,0 +1,39 @@
+package me.smartstore.menu;
+
+public class MainMenu implements Menu {
+
+    private final CustomerMenu customerMenu = CustomerMenu.getInstance();
+    private final GroupMenu groupMenu = GroupMenu.getInstance();
+    private final SummaryMenu summaryMenu = SummaryMenu.getInstance();
+
+    // singleton
+    private static MainMenu mainMenu;
+
+    public static MainMenu getInstance() {
+        if (mainMenu == null) {
+            mainMenu = new MainMenu();
+        }
+        return mainMenu;
+    }
+
+    private MainMenu() {}
+
+    @Override
+    public void manage() {
+        while ( true ) { // 프로그램 실행 while
+            int choice = mainMenu.chooseMenu(new String[] {
+                    "Parameter",
+                    "Customer",
+                    "Classification Summary",
+                    "Quit"});
+
+            if (choice == 1) groupMenu.manage();
+            else if (choice == 2) customerMenu.manage();
+            else if (choice == 3) summaryMenu.manage();
+            else { // choice == 4
+                System.out.println("Program Finished");
+                break;
+            }
+        }
+    }
+}
diff --git a/src/me/smartstore/menu/Menu.java b/src/me/smartstore/menu/Menu.java
new file mode 100644
index 00000000..4c907be4
--- /dev/null
+++ b/src/me/smartstore/menu/Menu.java
@@ -0,0 +1,48 @@
+package me.smartstore.menu;
+
+import me.smartstore.exception.InputEndException;
+import me.smartstore.exception.InputRangeException;
+import me.smartstore.util.Message;
+
+import java.util.InputMismatchException;
+import java.util.Scanner;
+
+public interface Menu {
+    Scanner scanner = new Scanner(System.in);
+
+    default String nextLine() { // 하나의 프로그램 상에서 nextLine() 함수를 통해서 사용자 입력을 받음
+        return scanner.nextLine().toUpperCase();
+    }
+
+    default String nextLine(Message end) {
+        System.out.println("** Press 'end', if you want to exit! **");
+        String str = scanner.nextLine().toUpperCase();
+        if (str.equals(end)) throw new InputEndException();
+        return str;
+    }
+
+    default int chooseMenu(String[] menus) {
+        while ( true ) { // 예외 복구 while
+            try {
+                System.out.println("===============================");
+                for (int i = 0; i < menus.length; i++) {
+                    System.out.printf(" %d. %s\n", i + 1, menus[i]);
+                }
+                System.out.println("===============================");
+                System.out.print("Choose One: ");
+                int choice = Integer.parseInt(nextLine());
+                if (choice >= 1 && choice <= menus.length) return choice;
+                throw new InputRangeException(); // choice 가 범위에 벗어남
+
+            } catch (InputMismatchException e) {
+                System.out.println(Message.ERR_MSG_INVALID_INPUT_FORMAT);
+
+            } catch (InputRangeException e) {
+                System.out.println(Message.ERR_MSG_INVALID_INPUT_RANGE);
+
+            }
+        }
+    }
+
+    void manage(); // 각 서브메뉴들을 관리하는 함수 (각 서브메뉴의 최상위 메뉴)
+}
\ No newline at end of file
diff --git a/src/me/smartstore/menu/SummaryMenu.java b/src/me/smartstore/menu/SummaryMenu.java
new file mode 100644
index 00000000..b86abb9a
--- /dev/null
+++ b/src/me/smartstore/menu/SummaryMenu.java
@@ -0,0 +1,27 @@
+package me.smartstore.menu;
+
+public class SummaryMenu implements Menu {
+    // singleton
+    private static SummaryMenu summaryMenu;
+
+    public static SummaryMenu getInstance() {
+        if (summaryMenu == null) {
+            summaryMenu = new SummaryMenu();
+        }
+        return summaryMenu;
+    }
+
+    private SummaryMenu() {}
+
+    @Override
+    public void manage() {
+        while ( true ) { // 서브 메뉴 페이지를 유지하기 위한 while
+            int choice = chooseMenu(new String[]{
+                    "Summary",
+                    "Summary (Sorted By Name)",
+                    "Summary (Sorted By Time)",
+                    "Summary (Sorted By Pay)",
+                    "Back"});
+        }
+    }
+}
\ No newline at end of file
diff --git a/src/me/smartstore/util/Message.java b/src/me/smartstore/util/Message.java
new file mode 100644
index 00000000..25989f93
--- /dev/null
+++ b/src/me/smartstore/util/Message.java
@@ -0,0 +1,25 @@
+package me.smartstore.util;
+
+
+public enum Message {
+    ERR_MSG_INVALID_ARR_EMPTY("No Customers. Please input one first."),
+    ERR_MSG_NULL_ARR_ELEMENT("Elements in Array has null. Array can't be sorted."),
+    ERR_MSG_INVALID_INPUT_NULL("Null Input. Please input something."),
+    ERR_MSG_INVALID_INPUT_EMPTY("Empty Input. Please input something."),
+    ERR_MSG_INVALID_INPUT_RANGE("Invalid Input. Please try again."),
+    ERR_MSG_INVALID_INPUT_TYPE("Invalid Type for Input. Please try again."),
+    ERR_MSG_INVALID_INPUT_FORMAT("Invalid Format for Input. Please try again."),
+    ERR_MSG_INPUT_END("END is pressed. Exit this menu."),
+    END_MSG("END");
+
+
+    private final String message;
+
+    Message(String message) {
+        this.message = message;
+    }
+
+    public String getMessage() {
+        return this.message;
+    }
+}
\ No newline at end of file
diff --git a/src/me/smartstore/util/Util.java b/src/me/smartstore/util/Util.java
new file mode 100644
index 00000000..f3805042
--- /dev/null
+++ b/src/me/smartstore/util/Util.java
@@ -0,0 +1,22 @@
+package me.smartstore.util;
+
+import java.util.Arrays;
+import java.util.Objects;
+
+public class Util {
+    public static boolean isAnyNUll(Object... objects) {
+        return Arrays.stream(objects).anyMatch(Objects::isNull);
+    }
+
+    public static boolean isAnyNonNUll(Object... objects) {
+        return Arrays.stream(objects).anyMatch(Objects::nonNull);
+    }
+
+    public static boolean isAllNUll(Object... objects) {
+        return Arrays.stream(objects).allMatch(Objects::isNull);
+    }
+
+    public static boolean isAllNonNUll(Object... objects) {
+        return Arrays.stream(objects).allMatch(Objects::nonNull);
+    }
+}