diff --git a/Main.class b/Main.class
new file mode 100644
index 00000000..85cce4d3
Binary files /dev/null and b/Main.class differ
diff --git a/Main.java b/Main.java
new file mode 100644
index 00000000..537b661a
--- /dev/null
+++ b/Main.java
@@ -0,0 +1,19 @@
+package me.smartstore;
+
+public class Main {
+    public static void main(String[] args) {
+        // SmartStoreApp.getInstance().test().run(); // function chaining
+        // // SmartStoreApp.getInstance().run();
+        Customer customerLee = new Customer();
+        customerLee.setCustomerName("이순신");
+        customerLee.setCustomerID(10010);
+        customerLee.bonusPoint = 1000;
+        System.out.println(customerLee.showCustomerInfo());
+
+        VIPCustomer customerKim = new VIPCustomer();
+        customerKim.setCustomerName("김유신");
+        customerKim.setCustomerID(10020);
+        customerKim.bonusPoint = 10000;
+        System.out.println(customerKim.showCustomerInfo());
+    }
+}
\ No newline at end of file
diff --git a/SmartStoreApp.java b/SmartStoreApp.java
new file mode 100644
index 00000000..d37ca9dd
--- /dev/null
+++ b/SmartStoreApp.java
@@ -0,0 +1,66 @@
+package me.smartstore;
+import me.smartstore.customers.Customer;
+import me.smartstore.customers.Customers;
+import me.smartstore.groups.Group;
+import me.smartstore.groups.GroupType;
+import me.smartstore.groups.Groups;
+import me.smartstore.groups.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 : 23.04.27");
+        System.out.println(" Copyright 2023 Eunbin All rights reserved.");
+        System.out.println("===========================================\n");
+    }
+
+    /**
+     * @return
+     */
+    public SmartStoreApp test() {
+        allGroups.add(new Group(new Parameter(10, 100000), GroupType.GENERAL));
+        allGroups.add(new Group(new Parameter(20, 200000), GroupType.VIP));
+        allGroups.add(new Group(new Parameter(30, 300000), GroupType.VVIP));
+
+        for (int i = 0; i < 26; i++) {
+            allCustomers.add(new Customer(
+                    Character.toString((char) ('a' + i)),
+                    (char) ('a' + i) + "123",
+                    ((int) (Math.random() * 5) + 1) * 10,
+                    ((int) (Math.random() * 5) + 1) * 100000));
+        }
+
+        System.out.println("allCustomers = " + allCustomers);
+        System.out.println("allGroups = " + allGroups);
+
+        // @TODO: refresh do not implemented yet.
+        allCustomers.refresh(allGroups);
+
+        return this; // smartStoreApp
+    }
+
+    public void run() {
+        details();
+        mainMenu.manage();
+
+    }
+}
\ No newline at end of file
diff --git a/SmartStoreApplication.class b/SmartStoreApplication.class
new file mode 100644
index 00000000..116b2f94
Binary files /dev/null and b/SmartStoreApplication.class differ
diff --git a/arrays/Collections.java b/arrays/Collections.java
new file mode 100644
index 00000000..77b6adda
--- /dev/null
+++ b/arrays/Collections.java
@@ -0,0 +1,14 @@
+package me.smartstore.arrays;
+
+public interface Collections<T> {
+
+    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);
+}
diff --git a/arrays/DArray.java b/arrays/DArray.java
new file mode 100644
index 00000000..f3e59412
--- /dev/null
+++ b/arrays/DArray.java
@@ -0,0 +1,163 @@
+package me.smartstore.arrays;
+
+import me.smartstore.exception.ElementNotFoundException;
+import me.smartstore.exception.NullArgumentException;
+import java.util.EmptyStackException;
+
+public class DArray<T> implements Collections<T> {
+    
+    protected static final int DEFAULT = 10;
+
+    protected T[] arrays;
+    protected int size;
+    protected int capacity;
+
+    public static int getDefault() {
+        return DEFAULT;
+    }
+
+    public T[] getArrays() {
+        return arrays;
+    }
+
+    public void setArrays(T[] arrays) {
+        this.arrays = arrays;
+    }
+
+    public int getSize() {
+        return size;
+    }
+
+    public void setSize(int size) {
+        this.size = size;
+    }
+
+    public int getCapacity() {
+        return capacity;
+    }
+
+    public void setCapacity(int capacity) {
+        this.capacity = 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;
+    }
+
+    @Override
+    public int size() {
+        return size;
+    }
+
+    protected int capacity() {
+        return capacity;
+    }
+
+    @Override
+    public T get(int index) throws IndexOutOfBoundsException {
+        if(index<0 || index>=size) throw new IndexOutOfBoundsException();
+        return arrays[index];
+    }
+
+    @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();
+
+        for(int i=0; i<size; i++) {
+            if(arrays[i] == null) continue;
+            if(arrays[i].equals(object)) return i;
+        }
+        throw new ElementNotFoundException();
+    }
+
+    @Override
+    public void add(T object) throws NullArgumentException {
+        if(object == null) throw new NullArgumentException();
+        if(size<capacity) {
+            arrays[size] = object;
+            size++;
+        } else {
+            grow();
+            add(object);
+        }
+    }
+
+    @Override
+    public void add(int index, T object) throws IndexOutOfBoundsException, NullPointerException {
+        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() {
+        return pop(size -1);
+    }
+
+    @Override
+    public T pop(int index) throws IndexOutOfBoundsException {
+        if(size == 0) throw new EmptyStackException();
+        if(index<0 || index>=size) throw new IndexOutOfBoundsException();
+
+        T popElement = arrays[index];
+        arrays[index] = null;
+
+        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;
+        arrays = java.util.Arrays.copyOf(arrays, capacity);
+
+    }
+
+    @Override
+    public String toString() {
+        String toStr = "";
+        for(int i=0; i<size; i++) {
+            toStr += (arrays[i] + "\n");
+        }
+        return toStr;
+    }
+   
+}
diff --git a/customers/ClassifiedCustomers.class b/customers/ClassifiedCustomers.class
new file mode 100644
index 00000000..de6ecd8b
Binary files /dev/null and b/customers/ClassifiedCustomers.class differ
diff --git a/customers/ClassifiedCustomersGroup.class b/customers/ClassifiedCustomersGroup.class
new file mode 100644
index 00000000..3476e6eb
Binary files /dev/null and b/customers/ClassifiedCustomersGroup.class differ
diff --git a/customers/Customer.class b/customers/Customer.class
new file mode 100644
index 00000000..751337bd
Binary files /dev/null and b/customers/Customer.class differ
diff --git a/customers/Customer.java b/customers/Customer.java
new file mode 100644
index 00000000..f25764e8
--- /dev/null
+++ b/customers/Customer.java
@@ -0,0 +1,90 @@
+package me.smartstore.customers;
+
+import java.util.Objects;
+
+public class Customer {
+    
+    private String cusName;
+    private String cusId;
+    private Integer cusTotalTime;
+    private Integer cusTotalPay;
+    public Customer() {}
+
+    public Customer(String cusId) {
+        this.cusId = cusId;
+    }
+
+    public Customer(String cusName, String cusId) {
+        this.cusName = cusName;
+        this.cusId = cusId;
+    }
+
+    /**
+     * @param string
+     * @param cusId
+     * @param cusTotalTime
+     * @param cusTotalPay
+     */
+    public Customer(String string, String cusId, Integer cusTotalTime, Integer cusTotalPay) {
+        this.cusName = string;
+        this.cusId = cusId;
+        this.cusTotalTime = cusTotalTime;
+        this.cusTotalPay = cusTotalPay;
+    }
+
+    public String getCusName() {
+        return cusName;
+    }
+
+    public void setCusName(String cusName) {
+        this.cusName = cusName;
+    }
+
+    public String getCusId() {
+        return cusId;
+    }
+
+    public void setCusId(String cusId) {
+        this.cusId = cusId;
+    }
+
+    public Integer getCusTotalTime() {
+        return cusTotalTime;
+    }
+
+    public void setCusTotalTime(Integer cusTotalTime) {
+        this.cusTotalTime = cusTotalTime;
+    }
+
+    public Integer getCusTotalPay() {
+        return cusTotalPay;
+    }
+
+    public void setCusTotalPay(Integer cusTotalPay) {
+        this.cusTotalPay = cusTotalPay;
+    }
+
+    @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(cusId, customer.cusId);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(cusId);
+    }
+
+    @Override
+    public String toString() {
+        return "Customer{"+
+                "cusName='"+ cusName + '\''+
+                ", cusId='"+ cusId + '\''+
+                ", cusTotalTime=" + cusTotalTime +
+                ", cusTotalPay=" + cusTotalPay + 
+                '}';
+    }
+
+}
\ No newline at end of file
diff --git a/customers/Customers.class b/customers/Customers.class
new file mode 100644
index 00000000..ba5ca699
Binary files /dev/null and b/customers/Customers.class differ
diff --git a/customers/Customers.java b/customers/Customers.java
new file mode 100644
index 00000000..8f753906
--- /dev/null
+++ b/customers/Customers.java
@@ -0,0 +1,27 @@
+package me.smartstore.customers;
+
+import me.smartstore.arrays.DArray;
+import me.smartstore.groups.Groups;
+
+public class Customers extends DArray<Customer> {
+
+    //singleton
+    private static Customers allCustomers;
+
+    public static Customers getInstance() {
+        if(allCustomers == null) {
+            allCustomers = new Customers();
+        }
+        return allCustomers;
+    }
+
+    private Customers() {}
+
+    //refresh 함수가 호출되는 경우
+    //1.분류기준 바뀔때
+    //2.새로운 고객이 들어올 때
+    public void refresh(Groups groups) {
+
+    }
+
+}
diff --git a/exception/ArrayEmptyException.class b/exception/ArrayEmptyException.class
new file mode 100644
index 00000000..8a7ba847
Binary files /dev/null and b/exception/ArrayEmptyException.class differ
diff --git a/exception/ArrayEmptyException.java b/exception/ArrayEmptyException.java
new file mode 100644
index 00000000..da3b1822
--- /dev/null
+++ b/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);
+    }
+
+    public ArrayEmptyException(String message) {
+        super(message);
+    }
+}
\ No newline at end of file
diff --git a/exception/ElementNotFoundException.java b/exception/ElementNotFoundException.java
new file mode 100644
index 00000000..86ba57e8
--- /dev/null
+++ b/exception/ElementNotFoundException.java
@@ -0,0 +1,22 @@
+package me.smartstore.exception;
+
+public class ElementNotFoundException extends RuntimeException {
+    public ElementNotFoundException() {
+    }
+
+    public ElementNotFoundException(String message) {
+        super(message);
+    }
+
+    public ElementNotFoundException(String message, Throwable cause) {
+        super(message, cause);
+    }
+
+    public ElementNotFoundException(Throwable cause) {
+        super(cause);
+    }
+
+    public ElementNotFoundException(String message, Throwable cause, boolean enableSuppression, boolean writableStackTrace) {
+        super(message, cause, enableSuppression, writableStackTrace);
+    }
+}
\ No newline at end of file
diff --git a/exception/EmptyArrayException.java b/exception/EmptyArrayException.java
new file mode 100644
index 00000000..c62e67c4
--- /dev/null
+++ b/exception/EmptyArrayException.java
@@ -0,0 +1,22 @@
+package me.smartstore.exception;
+
+public class EmptyArrayException extends RuntimeException {
+    public EmptyArrayException() {
+    }
+
+    public EmptyArrayException(String message) {
+        super(message);
+    }
+
+    public EmptyArrayException(String message, Throwable cause) {
+        super(message, cause);
+    }
+
+    public EmptyArrayException(Throwable cause) {
+        super(cause);
+    }
+
+    public EmptyArrayException(String message, Throwable cause, boolean enableSuppression, boolean writableStackTrace) {
+        super(message, cause, enableSuppression, writableStackTrace);
+    }
+}
\ No newline at end of file
diff --git a/exception/InputEmptyException.class b/exception/InputEmptyException.class
new file mode 100644
index 00000000..3242a6d6
Binary files /dev/null and b/exception/InputEmptyException.class differ
diff --git a/exception/InputEmptyException.java b/exception/InputEmptyException.java
new file mode 100644
index 00000000..163225c9
--- /dev/null
+++ b/exception/InputEmptyException.java
@@ -0,0 +1,13 @@
+package me.smartstore.exception;
+import me.smartstore.util.Message;
+
+public class InputEmptyException extends RuntimeException {
+
+    public InputEmptyException() {
+        super(Message.ERR_MSG_INVALID_INPUT_EMPTY);
+    }
+
+    public InputEmptyException(String message) {
+        super(message);
+    }
+}
\ No newline at end of file
diff --git a/exception/InputEndException.class b/exception/InputEndException.class
new file mode 100644
index 00000000..d75d02aa
Binary files /dev/null and b/exception/InputEndException.class differ
diff --git a/exception/InputEndException.java b/exception/InputEndException.java
new file mode 100644
index 00000000..154adeea
--- /dev/null
+++ b/exception/InputEndException.java
@@ -0,0 +1,12 @@
+package me.smartstore.exception;
+import me.smartstore.util.Message;
+
+public class InputEndException extends RuntimeException {
+    public InputEndException() {
+        super(Message.ERR_MSG_INPUT_END);
+    }
+
+    public InputEndException(String message) {
+        super(message);
+    }
+}
\ No newline at end of file
diff --git a/exception/InputFormatException.class b/exception/InputFormatException.class
new file mode 100644
index 00000000..7f800891
Binary files /dev/null and b/exception/InputFormatException.class differ
diff --git a/exception/InputFormatException.java b/exception/InputFormatException.java
new file mode 100644
index 00000000..e4565ec3
--- /dev/null
+++ b/exception/InputFormatException.java
@@ -0,0 +1,12 @@
+package me.smartstore.exception;
+import me.smartstore.util.Message;
+
+public class InputFormatException extends RuntimeException {
+    public InputFormatException() {
+        super(Message.ERR_MSG_INVALID_INPUT_FORMAT);
+    }
+
+    public InputFormatException(String message) {
+        super(message);
+    }
+}
\ No newline at end of file
diff --git a/exception/InputRangeException.class b/exception/InputRangeException.class
new file mode 100644
index 00000000..ebe4b9df
Binary files /dev/null and b/exception/InputRangeException.class differ
diff --git a/exception/InputRangeException.java b/exception/InputRangeException.java
new file mode 100644
index 00000000..ba1b95c2
--- /dev/null
+++ b/exception/InputRangeException.java
@@ -0,0 +1,12 @@
+package me.smartstore.exception;
+import me.smartstore.util.Message;
+
+public class InputRangeException extends RuntimeException {
+    public InputRangeException() {
+        super(Message.ERR_MSG_INVALID_INPUT_RANGE);
+    }
+
+    public InputRangeException(String message) {
+        super(message);
+    }
+}
\ No newline at end of file
diff --git a/exception/InputTypeException.class b/exception/InputTypeException.class
new file mode 100644
index 00000000..a11bb10c
Binary files /dev/null and b/exception/InputTypeException.class differ
diff --git a/exception/InputTypeException.java b/exception/InputTypeException.java
new file mode 100644
index 00000000..56a7e7fc
--- /dev/null
+++ b/exception/InputTypeException.java
@@ -0,0 +1,12 @@
+package me.smartstore.exception;
+import me.smartstore.util.Message;
+
+public class InputTypeException extends RuntimeException {
+    public InputTypeException() {
+        super(Message.ERR_MSG_INVALID_INPUT_TYPE);
+    }
+
+    public InputTypeException(String message) {
+        super(message);
+    }
+}
\ No newline at end of file
diff --git a/exception/NullArgumentException.java b/exception/NullArgumentException.java
new file mode 100644
index 00000000..f098c2b4
--- /dev/null
+++ b/exception/NullArgumentException.java
@@ -0,0 +1,22 @@
+package me.smartstore.exception;
+
+public class NullArgumentException extends RuntimeException {
+    public NullArgumentException() {
+    }
+
+    public NullArgumentException(String message) {
+        super(message);
+    }
+
+    public NullArgumentException(String message, Throwable cause) {
+        super(message, cause);
+    }
+
+    public NullArgumentException(Throwable cause) {
+        super(cause);
+    }
+
+    public NullArgumentException(String message, Throwable cause, boolean enableSuppression, boolean writableStackTrace) {
+        super(message, cause, enableSuppression, writableStackTrace);
+    }
+}
\ No newline at end of file
diff --git a/groups/Group.class b/groups/Group.class
new file mode 100644
index 00000000..21d23d0f
Binary files /dev/null and b/groups/Group.class differ
diff --git a/groups/Group.java b/groups/Group.java
new file mode 100644
index 00000000..42eeb460
--- /dev/null
+++ b/groups/Group.java
@@ -0,0 +1,51 @@
+package me.smartstore.groups;
+import java.util.Objects;
+
+public class Group {
+    private Parameter parameter; // 분류기준
+    private GroupType groupType; // 그룹 타입
+
+    public Group() {}
+
+    public Group(Parameter parameter, GroupType groupType) {
+        this.parameter = parameter;
+        this.groupType = groupType;
+    }
+
+    public Parameter getParameter() {
+        return parameter;
+    }
+
+    public void setParameter(Parameter parameter) {
+        this.parameter = parameter;
+    }
+
+    public GroupType getGroupType() {
+        return groupType;
+    }
+
+    public void setGroupType(GroupType groupType) {
+        this.groupType = groupType;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) return true;
+        if (o == null || getClass() != o.getClass()) return false;
+        Group group = (Group) o;
+        return Objects.equals(parameter, group.parameter) && groupType == group.groupType;
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(parameter, groupType);
+    }
+
+    @Override
+    public String toString() {
+        return "Group{" +
+                "parameter=" + parameter +
+                ", groupType=" + groupType +
+                '}';
+    }
+}
\ No newline at end of file
diff --git a/groups/GroupType.class b/groups/GroupType.class
new file mode 100644
index 00000000..0840b58c
Binary files /dev/null and b/groups/GroupType.class differ
diff --git a/groups/GroupType.java b/groups/GroupType.java
new file mode 100644
index 00000000..56d896c7
--- /dev/null
+++ b/groups/GroupType.java
@@ -0,0 +1,22 @@
+package me.smartstore.groups;
+
+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;
+    }
+}
\ No newline at end of file
diff --git a/groups/Groups.class b/groups/Groups.class
new file mode 100644
index 00000000..012ec591
Binary files /dev/null and b/groups/Groups.class differ
diff --git a/groups/Groups.java b/groups/Groups.java
new file mode 100644
index 00000000..b5e66358
--- /dev/null
+++ b/groups/Groups.java
@@ -0,0 +1,45 @@
+package me.smartstore.groups;
+import me.smartstore.arrays.DArray;
+
+public class Groups extends DArray<Group> {
+    // singleton
+    private static Groups allGroups;
+
+    public static Groups getInstance() {
+        if (allGroups == null) {
+            allGroups = new Groups();
+        }
+        return allGroups;
+    }
+
+    private Groups() {}
+
+    public Group find(GroupType groupType) {
+        // NOTE: 오류나는 코드
+        // arrays.length: capacity
+        // arrays.size: 실제 객체가 들어가있는 수
+//        System.out.println(size);
+//        for (int i = 0; i < size; i++) {
+//            if (arrays[i].getGroupType() == groupType) {
+//                return arrays[i];
+//            }
+//        }
+//        return null;
+
+
+        for (int i = 0; i < allGroups.size; i++) {
+            if (allGroups.get(i).getGroupType() == groupType) {
+                return allGroups.get(i);
+            }
+        }
+        return  null;
+
+//        for (int i = 0; i < this.size; i++) {
+//            if (this.get(i).getGroupType() == groupType) {
+//                return this.get(i);
+//            }
+//        }
+//
+//        return null;
+    }
+}
\ No newline at end of file
diff --git a/groups/Parameter.class b/groups/Parameter.class
new file mode 100644
index 00000000..16a9c8a9
Binary files /dev/null and b/groups/Parameter.class differ
diff --git a/groups/Parameter.java b/groups/Parameter.java
new file mode 100644
index 00000000..1e550859
--- /dev/null
+++ b/groups/Parameter.java
@@ -0,0 +1,53 @@
+package me.smartstore.groups;
+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 +
+                '}';
+    }
+}
\ No newline at end of file
diff --git a/menu/CustomerMenu.class b/menu/CustomerMenu.class
new file mode 100644
index 00000000..15fd658f
Binary files /dev/null and b/menu/CustomerMenu.class differ
diff --git a/menu/CustomerMenu.java b/menu/CustomerMenu.java
new file mode 100644
index 00000000..35234000
--- /dev/null
+++ b/menu/CustomerMenu.java
@@ -0,0 +1,29 @@
+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"});
+                    
+        }
+        
+    }
+}
\ No newline at end of file
diff --git a/menu/GroupMenu.class b/menu/GroupMenu.class
new file mode 100644
index 00000000..4ee0ceb3
Binary files /dev/null and b/menu/GroupMenu.class differ
diff --git a/menu/GroupMenu.java b/menu/GroupMenu.java
new file mode 100644
index 00000000..31ebd96d
--- /dev/null
+++ b/menu/GroupMenu.java
@@ -0,0 +1,79 @@
+package me.smartstore.menu;
+import me.smartstore.customers.Customers;
+import me.smartstore.exception.InputEndException;
+import me.smartstore.groups.Group;
+import me.smartstore.groups.GroupType;
+import me.smartstore.groups.Groups;
+import me.smartstore.groups.Parameter;
+import me.smartstore.util.Message;
+
+public class GroupMenu implements Menu {
+    private final Groups allGroups = Groups.getInstance();
+    private final Customers allCustomers = Customers.getInstance();
+    // singleton
+    private static GroupMenu groupMenu;
+
+    public static GroupMenu getInstance() {
+        if (groupMenu == null) {
+            groupMenu = new GroupMenu();
+        }
+        return groupMenu;
+    }
+
+    private GroupMenu() {}
+
+    @Override
+    public void manage() {
+        while ( true ) { // 서브 메뉴 페이지를 유지하기 위한 while
+            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 break; // choice == 4
+        }
+
+    }
+
+    public GroupType chooseGroup() {
+        while ( true ) {
+            try {
+                System.out.print("Which group (GENERAL (G), VIP (V), VVIP (VV))? ");
+                String choice = nextLine(Message.END_MSG);
+                // group (str) -> GroupType (enum)
+                // "VIP" -> GroupType.VIP
+
+                GroupType groupType = GroupType.valueOf(choice).replaceFullName();
+                return groupType;
+            } catch (InputEndException e) {
+                System.out.println(Message.ERR_MSG_INPUT_END);
+                return null;
+            } catch (IllegalArgumentException e) {
+                System.out.println(Message.ERR_MSG_INVALID_INPUT_RANGE);
+            }
+        }
+    }
+
+    public void setParameter() { // 초기화할 때만 호출 가능
+        while ( true ) {
+            GroupType groupType = chooseGroup();
+
+            // GroupType에 해당하는 group 객체를 찾아야 함
+            Group group = allGroups.find(groupType);
+            if (group != null && group.getParameter() != null) { // group.getParameter()이 null이 아니면 이미 초기화됨
+                System.out.println("\n" + group.getGroupType() + " group already exists.");
+                System.out.println("\n" + group);
+            } else {
+                Parameter parameter = new Parameter();
+                // time, pay 사용자 입력받은 후, 설정 필요
+
+                group.setParameter(parameter);
+                allCustomers.refresh(allGroups); // 파라미터가 변경되었거나 추가되는 경우, 고객 분류를 다시 해야함
+            }
+        }
+    }
+}
\ No newline at end of file
diff --git a/menu/MainMenu.java b/menu/MainMenu.java
new file mode 100644
index 00000000..7ba85d92
--- /dev/null
+++ b/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;
+            }
+        }
+    }
+}
\ No newline at end of file
diff --git a/menu/Menu.class b/menu/Menu.class
new file mode 100644
index 00000000..e789a30f
Binary files /dev/null and b/menu/Menu.class differ
diff --git a/menu/Menu.java b/menu/Menu.java
new file mode 100644
index 00000000..a2332ffb
--- /dev/null
+++ b/menu/Menu.java
@@ -0,0 +1,46 @@
+package me.smartstore.menu;
+import me.smartstore.exception.InputRangeException;
+import me.smartstore.exception.InputEndException;
+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(String 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/menu/OrderType.class b/menu/OrderType.class
new file mode 100644
index 00000000..b22deef4
Binary files /dev/null and b/menu/OrderType.class differ
diff --git a/menu/SummarizedMenu.class b/menu/SummarizedMenu.class
new file mode 100644
index 00000000..332f3bbd
Binary files /dev/null and b/menu/SummarizedMenu.class differ
diff --git a/menu/SummaryMenu.java b/menu/SummaryMenu.java
new file mode 100644
index 00000000..b37bb7c5
--- /dev/null
+++ b/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/util/Message.class b/util/Message.class
new file mode 100644
index 00000000..8e8789db
Binary files /dev/null and b/util/Message.class differ
diff --git a/util/Message.java b/util/Message.java
new file mode 100644
index 00000000..a3f73c1f
--- /dev/null
+++ b/util/Message.java
@@ -0,0 +1,13 @@
+package me.smartstore.util;
+
+public interface Message {
+    String ERR_MSG_INVALID_ARR_EMPTY = "No Customers. Please input one first.";
+    String ERR_MSG_NULL_ARR_ELEMENT = "Elements in Array has null. Array can't be sorted.";
+    String ERR_MSG_INVALID_INPUT_NULL = "Null Input. Please input something.";
+    String ERR_MSG_INVALID_INPUT_EMPTY = "Empty Input. Please input something.";
+    String ERR_MSG_INVALID_INPUT_RANGE = "Invalid Input. Please try again.";
+    String ERR_MSG_INVALID_INPUT_TYPE = "Invalid Type for Input. Please try again.";
+    String ERR_MSG_INVALID_INPUT_FORMAT = "Invalid Format for Input. Please try again.";
+    String ERR_MSG_INPUT_END = "END is pressed. Exit this menu.";
+    String END_MSG = "END";
+}
\ No newline at end of file
diff --git a/util/UtilMethod.class b/util/UtilMethod.class
new file mode 100644
index 00000000..24bd7273
Binary files /dev/null and b/util/UtilMethod.class differ