diff --git a/me/day05/practice/Practice01/AuthMethod.java b/me/day05/practice/Practice01/AuthMethod.java
new file mode 100644
index 0000000..a4bfe72
--- /dev/null
+++ b/me/day05/practice/Practice01/AuthMethod.java
@@ -0,0 +1,19 @@
+package me.day05.practice.Practice01;
+
+public enum AuthMethod {
+    FINGERPRINT("지문 인증"), PATTERN("패턴 인증"), PIN("핀 인증"), FACE("얼굴 인증"),;
+
+    private String authMethod = null;
+
+    AuthMethod(String authMethod) {
+        this.authMethod = authMethod;
+    }
+
+    public String getAuthMethod() {
+        return authMethod;
+    }
+
+    public void setAuthMethod(String authMethod) {
+        this.authMethod = authMethod;
+    }
+}
diff --git a/me/day05/practice/Practice01/Company.java b/me/day05/practice/Practice01/Company.java
new file mode 100644
index 0000000..f690f97
--- /dev/null
+++ b/me/day05/practice/Practice01/Company.java
@@ -0,0 +1,23 @@
+package me.day05.practice.Practice01;
+
+public enum Company {
+
+    SAMSUNG("SAMSUNG"), LG("LG"), APPLE("APPLE");
+
+    private String companyName;
+
+    Company(String companyName){
+        this.companyName = companyName;
+    }
+
+    public String getCompanyName() {
+        return companyName;
+    }
+
+    public void setCompanyName(String companyName) {
+        this.companyName = companyName;
+    }
+}
+
+
+
diff --git a/me/day05/practice/Practice01/Electronic.java b/me/day05/practice/Practice01/Electronic.java
new file mode 100644
index 0000000..efc3123
--- /dev/null
+++ b/me/day05/practice/Practice01/Electronic.java
@@ -0,0 +1,110 @@
+package me.day05.practice.Practice01;
+
+import java.time.LocalDate;
+import java.time.format.DateTimeFormatter;
+import java.util.ArrayList;
+import java.util.Objects;
+
+public class Electronic {
+
+    private static int modelCount = 0;
+
+    private String productNo;
+    private String modelName;
+    private Company companyName;
+    private LocalDate dateOfMade;
+    private ArrayList<AuthMethod> authMethod = new ArrayList<>();
+
+
+    public Electronic(String modelName, Company companyName, AuthMethod auth) {
+        this.productNo = setProductNo();
+        this.modelName = modelName;
+        this.companyName = companyName;
+        this.dateOfMade = setDateOfMade();
+        authMethod.add(auth);
+    }
+
+
+    public static int getModelCount() {
+        return modelCount;
+    }
+
+    public static void setModelCount(int modelCount) {
+        Electronic.modelCount = modelCount;
+    }
+
+    public String getProductNo() {
+        return productNo;
+    }
+
+
+    public String setProductNo() {
+        modelCount++;
+        LocalDate now = LocalDate.now();
+        String productNo = now.format(DateTimeFormatter.ofPattern("YYMMdd"));
+        productNo += String.format("%04d", modelCount);
+        return productNo;
+    }
+
+    private LocalDate setDateOfMade() {
+        LocalDate now = LocalDate.now();
+        return now;
+    }
+
+    public String getModelName() {
+        return modelName;
+    }
+
+    public void setModelName(String modelName) {
+        this.modelName = modelName;
+    }
+
+    public Company getCompanyName() {
+        return companyName;
+    }
+
+    public void setCompanyName(Company companyName) {
+        this.companyName = companyName;
+    }
+
+    public LocalDate getDateOfMade() {
+        return dateOfMade;
+    }
+
+    public void setDateOfMade(LocalDate dateOfMade) {
+        this.dateOfMade = dateOfMade;
+    }
+
+    public ArrayList<AuthMethod> getAuthMethod() {
+        return authMethod;
+    }
+
+    public void setAuthMethod(AuthMethod auth) {
+        authMethod.add(auth);
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) return true;
+        if (o == null || getClass() != o.getClass()) return false;
+        Electronic that = (Electronic) o;
+        return productNo.equals(that.productNo) && modelName.equals(that.modelName) && companyName.equals(that.companyName) && dateOfMade.equals(that.dateOfMade) && authMethod.equals(that.authMethod);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(productNo, modelName, companyName, dateOfMade, authMethod);
+    }
+
+    @Override
+    public String toString() {
+        return "Electronic{" +
+                "productNo='" + productNo + '\'' +
+                ", modelName='" + modelName + '\'' +
+                ", companyName='" + companyName + '\'' +
+                ", dateOfMade=" + dateOfMade +
+                ", authMethod=" + authMethod +
+                '}';
+    }
+
+}
diff --git a/me/day05/practice/Practice01/MainTest.java b/me/day05/practice/Practice01/MainTest.java
new file mode 100644
index 0000000..3fc2257
--- /dev/null
+++ b/me/day05/practice/Practice01/MainTest.java
@@ -0,0 +1,22 @@
+package me.day05.practice.Practice01;
+
+public class MainTest {
+    public static void main(String[] args) {
+        Electronic SMonitor = new Electronic("Monitor", Company.SAMSUNG, AuthMethod.FACE);
+        Electronic IMac = new Electronic("Mac", Company.APPLE, AuthMethod.FINGERPRINT);
+        Electronic Gram = new Electronic("Gram", Company.LG, AuthMethod.PIN);
+
+        User user01 = new User("Kim", "1234qwer", "01012345678", "Kim@naver.com", 19950927, Gram);
+        User user02 = new User("Park", "qwer1234asdf", "01012345678", "Park@mail.com", 19920901, null );
+
+        IMac.setAuthMethod(AuthMethod.PATTERN);
+        Gram.setAuthMethod(AuthMethod.FACE);
+
+        user02.addElectronicDevices(SMonitor);
+        user02.addElectronicDevices(IMac);
+
+        System.out.println(user01);
+        System.out.println(user02);
+
+    }
+}
diff --git a/me/day05/practice/Practice01/User.java b/me/day05/practice/Practice01/User.java
new file mode 100644
index 0000000..b1c1970
--- /dev/null
+++ b/me/day05/practice/Practice01/User.java
@@ -0,0 +1,112 @@
+package me.day05.practice.Practice01;
+
+import java.time.LocalDateTime;
+import java.util.ArrayList;
+import java.util.Objects;
+
+public class User {
+    private String userId;
+    private String userPassword;
+    private String userPhoneNumber;
+    private String userEmail;
+    private int userBirthDate;
+    private ArrayList<Electronic> electronicDevices = new ArrayList<>();
+    private LocalDateTime registerTime;
+
+    public User(String userId, String userPassword, String userPhoneNumber, String userEmail, int userBirthDay, Electronic electronic) {
+        this.userId = userId;
+        this.userPassword = userPassword;
+        this.userPhoneNumber = userPhoneNumber;
+        this.userEmail = userEmail;
+        this.userBirthDate = userBirthDay;
+        this.registerTime = LocalDateTime.now();
+        electronicDevices.add(electronic);
+    }
+
+
+    public String getUserId() {
+        return userId;
+    }
+
+    public void setUserId(String userId) {
+        this.userId = userId;
+    }
+
+    public String getUserPassword() {
+        return userPassword;
+    }
+
+    public void setUserPassword(String userPassword) {
+        this.userPassword = userPassword;
+    }
+
+    public String getUserPhoneNumber() {
+        return userPhoneNumber;
+    }
+
+    public void setUserPhoneNumber(String userPhoneNumber) {
+        this.userPhoneNumber = userPhoneNumber;
+    }
+
+    public String getUserEmail() {
+        return userEmail;
+    }
+
+    public void setUserEmail(String userEmail) {
+        this.userEmail = userEmail;
+    }
+
+    public int getUserBirthDate() {
+        return userBirthDate;
+    }
+
+    public void setUserBirthDate(int userBirthDate) {
+        this.userBirthDate = userBirthDate;
+    }
+
+    public ArrayList<Electronic> getElectronicDevices() {
+        return electronicDevices;
+    }
+
+    public void setElectronicDevices(ArrayList<Electronic> electronicDevices) {
+        this.electronicDevices = electronicDevices;
+    }
+
+     public void addElectronicDevices(Electronic devices) {
+        electronicDevices.add(devices);
+    }
+
+    public LocalDateTime getRegisterTime() {
+        return registerTime;
+    }
+
+    public void setRegisterTime(LocalDateTime registerTime) {
+        this.registerTime = registerTime;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) return true;
+        if (o == null || getClass() != o.getClass()) return false;
+        User user = (User) o;
+        return userPhoneNumber == user.userPhoneNumber && userBirthDate == user.userBirthDate && userId.equals(user.userId) && userPassword.equals(user.userPassword) && userEmail.equals(user.userEmail) && electronicDevices.equals(user.electronicDevices) && registerTime.equals(user.registerTime);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(userId, userPassword, userPhoneNumber, userEmail, userBirthDate, electronicDevices, registerTime);
+    }
+
+    @Override
+    public String toString() {
+        return "User{" +
+                "userId='" + userId + '\'' +
+                ", userPassword='" + userPassword + '\'' +
+                ", userPhoneNumber=" + userPhoneNumber +
+                ", userEmail='" + userEmail + '\'' +
+                ", userBirthDate=" + userBirthDate +
+                ", electronicDevices=" + electronicDevices +
+                ", registerTime=" + registerTime +
+                '}';
+    }
+}
diff --git a/me/day05/practice/Practice02/Users.java b/me/day05/practice/Practice02/Users.java
new file mode 100644
index 0000000..463a0c6
--- /dev/null
+++ b/me/day05/practice/Practice02/Users.java
@@ -0,0 +1,86 @@
+package me.day05.practice.Practice02;
+
+import me.day05.practice.Practice01.Electronic;
+import me.day05.practice.Practice01.User;
+
+import java.util.Arrays;
+
+public class Users {
+
+    private static Users usersInstance;
+
+    private Users(){
+    }
+
+    //1.싱글톤
+
+    public static Users getInstance() {
+        if(usersInstance==null) {
+            usersInstance = new Users();
+        }
+        return usersInstance;
+    }
+
+    public static Users getUsersInstance() {
+        return usersInstance;
+    }
+
+    public static void setUsersInstance(Users usersInstance) {
+        Users.usersInstance = usersInstance;
+    }
+
+    private User[] userList;
+
+    public User[] getUserList() {
+        return userList;
+    }
+
+    public void setUserList(User[] userList) {
+        this.userList = userList;
+    }
+
+
+    //2. 함수 반환
+    public User findByUserId(String userId) {
+        for(User user : userList) {
+            if(user.getUserId().equals(userId)) {
+                return user;
+            }
+        }
+        return null;
+    }
+
+    //3. deep copy?
+
+    public User copy(User user) {
+        User copyUser = new User(user.getUserId(),
+                user.getUserPassword(),
+                user.getUserEmail(),
+                user.getUserPhoneNumber(),
+                user.getUserBirthDate(),
+                user.getElectronicDevices().get(1));
+        return copyUser;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) return true;
+        if (o == null || getClass() != o.getClass()) return false;
+        Users users = (Users) o;
+        return Arrays.equals(userList, users.userList);
+    }
+
+    @Override
+    public int hashCode() {
+        return Arrays.hashCode(userList);
+    }
+    @Override
+    public String toString() {
+        return "Users{" +
+                "userList=" + Arrays.toString(userList) +
+                '}';
+    }
+
+
+
+}
diff --git a/me/day05/practice/Practice03/Electronics.java b/me/day05/practice/Practice03/Electronics.java
new file mode 100644
index 0000000..07db31e
--- /dev/null
+++ b/me/day05/practice/Practice03/Electronics.java
@@ -0,0 +1,178 @@
+package me.day05.practice.Practice03;
+
+import me.day05.practice.Practice01.AuthMethod;
+import me.day05.practice.Practice01.Company;
+import me.day05.practice.Practice01.Electronic;
+
+
+import java.time.LocalDate;
+import java.time.format.DateTimeFormatter;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Objects;
+
+public class Electronics {
+
+    private static Electronics usersInstance;
+
+    private Electronics(){
+    }
+
+    private  Electronic[] electronicList;
+
+    private static int modelCount = 0;
+
+    private String productNo;
+    private String modelName;
+    private Company companyName;
+    private LocalDate dateOfMade;
+    private ArrayList<AuthMethod> authMethod = new ArrayList<>();
+
+
+    public Electronics(String modelName, Company companyName, AuthMethod auth) {
+        this.productNo = setProductNo();
+        this.modelName = modelName;
+        this.companyName = companyName;
+        this.dateOfMade = setDateOfMade();
+        authMethod.add(auth);
+    }
+
+
+    public static int getModelCount() {
+        return modelCount;
+    }
+
+    public static void setModelCount(int modelCount) {
+        Electronics.modelCount = modelCount;
+    }
+
+    public String getProductNo() {
+        return productNo;
+    }
+
+
+    public String setProductNo() {
+        modelCount++;
+        LocalDate now = LocalDate.now();
+        String productNo = now.format(DateTimeFormatter.ofPattern("YYMMdd"));
+        productNo += String.format("%04d", modelCount);
+        return productNo;
+    }
+
+    private LocalDate setDateOfMade() {
+        LocalDate now = LocalDate.now();
+        return now;
+    }
+
+    public String getModelName() {
+        return modelName;
+    }
+
+    public void setModelName(String modelName) {
+        this.modelName = modelName;
+    }
+
+    public Company getCompanyName() {
+        return companyName;
+    }
+
+    public void setCompanyName(Company companyName) {
+        this.companyName = companyName;
+    }
+
+    public LocalDate getDateOfMade() {
+        return dateOfMade;
+    }
+
+    public void setDateOfMade(LocalDate dateOfMade) {
+        this.dateOfMade = dateOfMade;
+    }
+
+    public ArrayList<AuthMethod> getAuthMethod() {
+        return authMethod;
+    }
+
+    public void setAuthMethod(AuthMethod auth) {
+        authMethod.add(auth);
+    }
+
+    public Electronic[] getElectronicList() {
+        return electronicList;
+    }
+
+    public void setElectronicList(Electronic[] electronicList) {
+        this.electronicList = electronicList;
+    }
+
+
+
+    //1. 싱글톤
+    public static Electronics getInstance() {
+        if(usersInstance==null) {
+            usersInstance = new Electronics();
+        }
+        return usersInstance;
+    }
+
+    //2. 함수 반환
+    public Electronic findByProductNo(String productNo){
+        for(Electronic electronic : electronicList) {
+            if(electronic.getProductNo().equals(productNo)){
+                return electronic;
+            }
+        }
+        return null;
+    }
+
+
+    //3. 제조 회사
+    public Electronic[] groupByCompanyName(Company company) {
+         List<Electronic> groupCompanyList = new ArrayList<>();
+             for (Electronic electronic : electronicList) {
+                  if (electronic.getCompanyName().equals(company)) {
+                    groupCompanyList.add(electronic);
+                   }
+
+             }
+             return groupCompanyList.toArray(new Electronic[groupCompanyList.size()]);
+    }
+
+
+    //4. 인증 방법
+
+    public Electronic[] groupByAuthMethod(AuthMethod authMethod) {
+        List<Electronic> groupAuthMethod = new ArrayList<>();
+        for (Electronic electronic : electronicList) {
+            if (electronic.getAuthMethod().equals(authMethod)) {
+                groupAuthMethod.add(electronic);
+            }
+
+        }
+        return groupAuthMethod.toArray(new Electronic[groupAuthMethod.size()]);
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) return true;
+        if (o == null || getClass() != o.getClass()) return false;
+        Electronics that = (Electronics) o;
+        return productNo.equals(that.productNo) && modelName.equals(that.modelName) && companyName.equals(that.companyName) && dateOfMade.equals(that.dateOfMade) && authMethod.equals(that.authMethod);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(productNo, modelName, companyName, dateOfMade, authMethod);
+    }
+
+    @Override
+    public String toString() {
+        return "Electronic{" +
+                "productNo='" + productNo + '\'' +
+                ", modelName='" + modelName + '\'' +
+                ", companyName='" + companyName + '\'' +
+                ", dateOfMade=" + dateOfMade +
+                ", authMethod=" + authMethod +
+                '}';
+    }
+
+}