diff --git a/src/me/day05/practice/Practice01/Auth.java b/src/me/day05/practice/Practice01/Auth.java
new file mode 100644
index 0000000..613695d
--- /dev/null
+++ b/src/me/day05/practice/Practice01/Auth.java
@@ -0,0 +1,5 @@
+package me.day05.practice.Practice01;
+
+public enum Auth {
+   FingerPrint,Pattern,PIN,Face;
+}
diff --git a/src/me/day05/practice/Practice01/Company.java b/src/me/day05/practice/Practice01/Company.java
new file mode 100644
index 0000000..25b8c25
--- /dev/null
+++ b/src/me/day05/practice/Practice01/Company.java
@@ -0,0 +1,5 @@
+package me.day05.practice.Practice01;
+
+public enum Company {
+        SAMSUNG,LG,APPLE;
+}
diff --git a/src/me/day05/practice/Practice01/Electronic.java b/src/me/day05/practice/Practice01/Electronic.java
new file mode 100644
index 0000000..36a9c07
--- /dev/null
+++ b/src/me/day05/practice/Practice01/Electronic.java
@@ -0,0 +1,99 @@
+package me.day05.practice.Practice01;
+
+import java.time.LocalDate;
+import java.time.format.DateTimeFormatter;
+import java.util.Objects;
+
+public class Electronic {
+    private static int serialNum = 0;
+
+    private String productNO;
+    private String modelName;
+    private Company CompanyName;
+    private LocalDate dateOfMade;
+    private Auth[] authMethod;
+
+    public Electronic(String modelName, Company companyName, Auth[] authMethod) {
+        serialNum++;
+        productNO = setProductNO();
+        this.modelName = modelName;
+        CompanyName = companyName;
+        this.dateOfMade = LocalDate.now();
+        this.authMethod = authMethod;
+    }
+
+    public Electronic() {
+        serialNum++;
+        productNO = setProductNO();
+    }
+
+    public String getProductNO() {
+        return productNO;
+    }
+
+    public String setProductNO() {
+        LocalDate localDate = LocalDate.now();
+        String serialNO = localDate.format(DateTimeFormatter.ofPattern("yyMMdd"));
+        serialNO += String.format("%04d",serialNum);
+
+        return serialNO;
+    }
+
+    public String getModelName() {
+        return modelName;
+    }
+
+    public void setModelName(String modelName) {
+        this.modelName = modelName;
+    }
+
+    public Company getCompanyName() {
+        return CompanyName;
+    }
+
+    public void setCompanyName(Company companyName) {
+        CompanyName = companyName;
+    }
+
+    public LocalDate getDateOfMade() {
+        return dateOfMade;
+    }
+
+    public void setDateOfMade(LocalDate dateOfMade) {
+        this.dateOfMade = dateOfMade;
+    }
+
+    public Auth[] getAuthMethod() {
+        return authMethod;
+    }
+
+    public void setAuthMethod(Auth[] authMethod) {
+        this.authMethod = authMethod;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) return true;
+        if (o == null || getClass() != o.getClass()) return false;
+        Electronic that = (Electronic) o;
+        return Objects.equals(productNO, that.productNO) && Objects.equals(modelName, that.modelName) && CompanyName == that.CompanyName && Objects.equals(dateOfMade, that.dateOfMade) && authMethod == 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/src/me/day05/practice/Practice01/User.java b/src/me/day05/practice/Practice01/User.java
new file mode 100644
index 0000000..f473b39
--- /dev/null
+++ b/src/me/day05/practice/Practice01/User.java
@@ -0,0 +1,120 @@
+package me.day05.practice.Practice01;
+
+import java.time.LocalDateTime;
+import java.time.format.DateTimeFormatter;
+import java.util.Arrays;
+import java.util.Objects;
+
+public class User {
+
+    private String userId;
+    private String userPassword;
+    private String userPhoneNumber;
+    private String userEmail;
+    private String userBirthDate;
+    private Electronic[] electronicDevices;
+    private LocalDateTime registerTime;
+    static final int DEFAULT_CAPACITY = 10;
+
+    public User(String userId, String userPassword, String userPhoneNumber, String userEmail, String userBirthDate, Electronic[] electronicDevices, LocalDateTime registerTime) {
+        this.userId = userId;
+        this.userPassword = userPassword;
+        this.userPhoneNumber = userPhoneNumber;
+        this.userEmail = userEmail;
+        this.userBirthDate = userBirthDate;
+        this.electronicDevices = new Electronic[DEFAULT_CAPACITY];
+        this.registerTime = LocalDateTime.now();
+    }
+
+    public User() {
+        this.electronicDevices = new Electronic[DEFAULT_CAPACITY];
+        this.registerTime = LocalDateTime.now();
+    }
+
+    public String getUserId() {
+
+        return userId;
+    }
+
+    public void setUserId(String userId) {
+        this.userId = userId;
+    }
+
+    @Override
+    public String toString() {
+        return "User{" +
+                "userId='" + userId + '\'' +
+                ", userPassword='" + userPassword + '\'' +
+                ", userPhoneNumber='" + userPhoneNumber + '\'' +
+                ", userEmail='" + userEmail + '\'' +
+                ", userBirthDate='" + userBirthDate + '\'' +
+                ", electronicDevices=" + Arrays.toString(electronicDevices) +
+                ", registerTime=" + registerTime +
+                '}';
+    }
+
+    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 String getUserBirthDate() {
+        return userBirthDate;
+    }
+
+    public void setUserBirthDate(String userBirthDate) {
+        this.userBirthDate = userBirthDate;
+    }
+
+    public Electronic[] getElectronicDevices() {
+        return electronicDevices;
+    }
+
+    public void setElectronicDevices(Electronic[] electronicDevices) {
+        this.electronicDevices = electronicDevices;
+    }
+
+    public String getRegisterTime() { // 원하는 패턴으로 반환
+        return registerTime.format(DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss"));
+    }
+
+    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 Objects.equals(userId, user.userId) && Objects.equals(userPassword, user.userPassword) && Objects.equals(userPhoneNumber, user.userPhoneNumber) && Objects.equals(userEmail, user.userEmail) && Objects.equals(userBirthDate, user.userBirthDate) && Arrays.equals(electronicDevices, user.electronicDevices) && Objects.equals(registerTime, user.registerTime);
+    }
+
+    @Override
+    public int hashCode() {
+        int result = Objects.hash(userId, userPassword, userPhoneNumber, userEmail, userBirthDate, registerTime);
+        result = 31 * result + Arrays.hashCode(electronicDevices);
+        return result;
+    }
+
+
+}
diff --git a/src/me/day05/practice/Practice02/Users.java b/src/me/day05/practice/Practice02/Users.java
new file mode 100644
index 0000000..d9717d4
--- /dev/null
+++ b/src/me/day05/practice/Practice02/Users.java
@@ -0,0 +1,83 @@
+package me.day05.practice.Practice02;
+
+import me.day05.practice.Practice01.User;
+
+import java.util.ArrayList;
+import java.util.Objects;
+
+public class Users {
+    private ArrayList<User> userList = new ArrayList<>();
+
+    public Users(ArrayList<User> userList) {
+        this.userList = userList;
+    }
+
+    public Users () {}
+    public ArrayList<User> getUserList() {
+        return userList;
+    }
+
+    public void setUserList(ArrayList<User> userList) {
+        this.userList = userList;
+    }
+
+    public static void setInstance(Users instance) {
+        Users.instance = instance;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) return true;
+        if (o == null || getClass() != o.getClass()) return false;
+        Users users = (Users) o;
+        return Objects.equals(userList, users.userList);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(userList);
+    }
+
+    @Override
+    public String toString() {
+        return "Users{" +
+                "userList=" + userList +
+                '}';
+    }
+
+    // Users 클래스의 객체를 싱글톤으로 생성하는 함수를 작성하시오.
+    private static Users instance;
+    public static Users getInstance() {
+        if (instance == null) {
+            instance = new Users();
+        }
+
+        return instance;
+    }
+
+
+    //회원 아이디 userId를 통해 인자로 주어진 회원번호에 해당하는 회원을 반환하는 함수를 작성하시오
+
+    public User findByUserId(String userId) {
+        for (User user : userList) {
+            if (userId.equals(user.getUserId())) {
+                return user;
+            }
+        }
+        return null;
+    }
+
+// 인자로 주어진 회원 정보를 깊은 복사 (deepCopy) 하는 함수를 작성하시오.
+    public User Copy(User user) {
+        User userCopy = new User();
+        userCopy.setUserId(user.getUserId());
+        userCopy.setUserPassword(user.getUserPassword());
+        userCopy.setUserEmail(user.getUserEmail());
+        userCopy.setUserPhoneNumber(user.getUserPhoneNumber());
+        userCopy.setUserBirthDate(user.getUserBirthDate());
+        userCopy.setElectronicDevices(user.getElectronicDevices());
+
+        return userCopy;
+    }
+
+}
diff --git a/src/me/day05/practice/Practice03/Electronics.java b/src/me/day05/practice/Practice03/Electronics.java
new file mode 100644
index 0000000..5cd798e
--- /dev/null
+++ b/src/me/day05/practice/Practice03/Electronics.java
@@ -0,0 +1,92 @@
+package me.day05.practice.Practice03;
+
+
+import me.day05.practice.Practice01.Auth;
+import me.day05.practice.Practice01.Company;
+import me.day05.practice.Practice01.Electronic;
+
+import java.util.ArrayList;
+import java.util.Objects;
+
+public class Electronics {
+    private ArrayList<Electronic> electronicList = new ArrayList<>();
+
+    public Electronics(ArrayList<Electronic> electronicList) {
+        this.electronicList = electronicList;
+    }
+
+    public Electronics() {}
+    public ArrayList<Electronic> getElectronicList() {
+        return electronicList;
+    }
+
+    public void setElectronicList(ArrayList<Electronic> electronicList) {
+        this.electronicList = electronicList;
+    }
+
+    public static void setInstance(Electronics instance) {
+        Electronics.instance = instance;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) return true;
+        if (o == null || getClass() != o.getClass()) return false;
+        Electronics that = (Electronics) o;
+        return Objects.equals(electronicList, that.electronicList);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(electronicList);
+    }
+
+    @Override
+    public String toString() {
+        return "Electronics{" +
+                "electronicList=" + electronicList +
+                '}';
+    }
+
+    // Electric 클래스의 객체를 싱글톤으로 생성하는 함수를 작성하시오.
+    private static Electronics instance;
+    public static Electronics getInstance() {
+        if (instance == null) {
+            instance = new Electronics();
+        }
+        return instance;
+    }
+
+    //전자제품 일련번호 productNo를 통해 인자로 주어진 일련번호에 해당하는 전자제품을 반환하는 함수를 작성하시오.
+    public Electronic findByUserId(String productNo){
+        for (Electronic electronic : electronicList){
+            if(electronic.setProductNO().equals(productNo)){
+                return electronic;
+            }
+        }
+        return null;
+    }
+    // 전자제품들 중 인자로 주어진 제조 회사를 찾아서 하나의 배열에 반환하는 함수를 작성하시오.
+    public ArrayList<Electronic> groupByCompanyName(Company company) {
+        ArrayList<Electronic> companyName = new ArrayList<>();
+
+        for(int i = 0; i < electronicList.size(); i++) {
+            if(electronicList.get(i).getCompanyName().equals(company)) {
+                companyName.add(electronicList.get(i));
+            }
+        }
+        return companyName;
+    }
+    //전자제품들 중 인자로 주어진 인증 방법을 찾아서 하나의 배열에 반환하는 함수를 작성하시오.
+    public ArrayList<Electronic> groupByAuthMethod(Auth[] authMethod) {
+        ArrayList<Electronic> authMethodGroupList = new ArrayList<>();
+
+        for(int i = 0; i < electronicList.size(); i++) {
+            if(electronicList.get(i).getAuthMethod().equals(authMethod)) {
+                authMethodGroupList.add(electronicList.get(i));
+            }
+        }
+        return authMethodGroupList;
+    }
+}
+