diff --git a/me/practice/Practice01/AuthMethod.java b/me/practice/Practice01/AuthMethod.java
new file mode 100644
index 0000000..87b662f
--- /dev/null
+++ b/me/practice/Practice01/AuthMethod.java
@@ -0,0 +1,5 @@
+package KDTBE5_Java_Assignment3.me.practice.Practice01;
+
+public enum AuthMethod {
+    지문인증, 패턴인증, 핀인증,얼굴인증
+}
diff --git a/me/practice/Practice01/Company.java b/me/practice/Practice01/Company.java
new file mode 100644
index 0000000..812324e
--- /dev/null
+++ b/me/practice/Practice01/Company.java
@@ -0,0 +1,5 @@
+package KDTBE5_Java_Assignment3.me.practice.Practice01;
+
+public enum Company {
+    SAMSUNG,LG,APPLE;
+}
diff --git a/me/practice/Practice01/Electronic.java b/me/practice/Practice01/Electronic.java
new file mode 100644
index 0000000..573c9c2
--- /dev/null
+++ b/me/practice/Practice01/Electronic.java
@@ -0,0 +1,96 @@
+package KDTBE5_Java_Assignment3.me.practice.Practice01;
+
+import java.time.format.DateTimeFormatter;
+import java.util.Arrays;
+import java.util.Objects;
+
+import static java.time.LocalDate.now;
+
+public class Electronic {
+    public static int registerNumber = 0;
+    private String productNo;
+    private Company companyName;
+    private String modelName;
+    private String dateOfMade;
+    private AuthMethod[] authMethod;
+
+    public Electronic(Company companyName, String modelName, String dateOfMade, AuthMethod[] authMethod) {
+        this.productNo = setProductNo();
+        this.companyName = companyName;
+        this.modelName = modelName;
+        this.dateOfMade = dateOfMade;
+        this.authMethod = authMethod;
+    }
+
+    private String setProductNo() {
+        String productNo = now().format(DateTimeFormatter.ofPattern("yyMMdd"))+String.format("%04d",++Electronic.registerNumber);
+        return productNo;
+    }
+
+
+    public String getProductNo() {
+        return productNo;
+    }
+
+    public void setProductNo(String productNo) {
+        this.productNo = productNo;
+    }
+
+    public Company getCompany() {
+        return companyName;
+    }
+
+    public void setCompany(Company companyName) {
+        this.companyName = companyName;
+    }
+
+    public String getModelName() {
+        return modelName;
+    }
+
+    public void setModelName(String modelName) {
+        this.modelName = modelName;
+    }
+
+    public String getDateOfMade() {
+        return dateOfMade;
+    }
+
+    public void setDateOfMade(String dateOfMade) {
+        this.dateOfMade = dateOfMade;
+    }
+
+    public AuthMethod[] getAuthMethod() {
+        return authMethod;
+    }
+
+    public void setAuthMethod(AuthMethod[] 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) && companyName == that.companyName && Objects.equals(modelName, that.modelName) && Objects.equals(dateOfMade, that.dateOfMade) && Arrays.equals(authMethod, that.authMethod);
+    }
+
+    @Override
+    public int hashCode() {
+        int result = Objects.hash(productNo, companyName, modelName, dateOfMade);
+        result = 31 * result + Arrays.hashCode(authMethod);
+        return result;
+    }
+
+    @Override
+    public String toString() {
+        return "Electronic{" +
+                "productNo='" + productNo + '\'' +
+                ", companyName=" + companyName +
+                ", modelName='" + modelName + '\'' +
+                ", dateOfMade='" + dateOfMade + '\'' +
+                ", authMethod=" + Arrays.toString(authMethod) +
+                '}';
+    }
+}
diff --git a/me/practice/Practice01/User.java b/me/practice/Practice01/User.java
new file mode 100644
index 0000000..952d180
--- /dev/null
+++ b/me/practice/Practice01/User.java
@@ -0,0 +1,110 @@
+package KDTBE5_Java_Assignment3.me.practice.Practice01;
+
+import java.time.chrono.ChronoLocalDateTime;
+import java.time.format.DateTimeFormatter;
+import java.util.Arrays;
+import java.util.Formatter;
+import java.util.Objects;
+
+import static java.time.LocalDateTime.now;
+
+public class User {
+    private String userId;
+    private String userPassword;
+    private String userEmail;
+    private String userBirthDate;
+    private Electronic [] electronicDevices;
+    private String registerTime;
+
+    public User() {
+
+    }
+
+    public User(String userId, String userPassword, String userEmail, String userBirthDate, Electronic[] electronicDevices) {
+        this.userId = userId;
+        this.userPassword = userPassword;
+        this.userEmail = userEmail;
+        this.userBirthDate = userBirthDate;
+        this.electronicDevices = electronicDevices;
+        this.registerTime = now().format(DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss"));
+    }
+//    public User(String userId, String userPassword, String userEmail, String userBirthDate, Electronic[] electronicDevices,String registerTime) {
+//        this.userId = userId;
+//        this.userPassword = userPassword;
+//        this.userEmail = userEmail;
+//        this.userBirthDate = userBirthDate;
+//        this.electronicDevices = electronicDevices;
+//        this.registerTime = registerTime;
+//    }
+
+    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 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() {
+        return registerTime;
+    }
+
+//    @Override
+//    public String toString() {
+//        return "User{" +
+//                "userId='" + userId + '\'' +
+//                ", userPassword='" + userPassword + '\'' +
+//                ", userEmail='" + userEmail + '\'' +
+//                ", userBirthDate='" + userBirthDate + '\'' +
+//                ", electronicDevices=" + Arrays.toString(electronicDevices) +
+//                ", 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(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, userEmail, userBirthDate, registerTime);
+        result = 31 * result + Arrays.hashCode(electronicDevices);
+        return result;
+    }
+}
diff --git a/me/practice/Practice02/Users.java b/me/practice/Practice02/Users.java
new file mode 100644
index 0000000..71f974b
--- /dev/null
+++ b/me/practice/Practice02/Users.java
@@ -0,0 +1,65 @@
+package KDTBE5_Java_Assignment3.me.practice.Practice02;
+
+import KDTBE5_Java_Assignment3.me.practice.Practice01.User;
+
+import java.util.Arrays;
+
+public class Users {
+    private static final Users INSTANCE = new Users();
+    public Users() {
+    }
+
+    public static Users getINSTANCE() {
+        return INSTANCE;
+    }
+
+    private User[]  users;
+
+
+    public User[] getUsers() {
+        return users;
+    }
+
+    public void setUsers(User[] users) {
+        this.users = users;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) return true;
+        if (o == null || getClass() != o.getClass()) return false;
+        Users users1 = (Users) o;
+        return Arrays.equals(users, users1.users);
+    }
+
+    @Override
+    public int hashCode() {
+        return Arrays.hashCode(users);
+    }
+
+    @Override
+    public String toString() {
+        return "Users{" +
+                "users=" + Arrays.toString(users) +
+                '}';
+    }
+
+    public User findUserId(String userId) throws Exception {
+        for (User user: this.users) {
+            if(user.getUserId().equals(userId))return user;
+        }
+        throw new Exception("해당 유저 아이디를 가진 유저는 존재하지 않습니다.");
+    }
+
+
+    public User copy(User user){
+        User clone = new User();
+        String userId = new String(user.getUserId());
+        clone.setUserId(userId);
+        clone.setUserPassword(user.getUserPassword());
+        clone.setUserEmail(user.getUserEmail());
+        clone.setUserBirthDate(user.getUserBirthDate());
+        clone.setElectronicDevices(user.getElectronicDevices());
+        return clone;
+    }
+}
diff --git a/me/practice/Practice03/Electronics.java b/me/practice/Practice03/Electronics.java
new file mode 100644
index 0000000..ce4dfe2
--- /dev/null
+++ b/me/practice/Practice03/Electronics.java
@@ -0,0 +1,84 @@
+package KDTBE5_Java_Assignment3.me.practice.Practice03;
+
+import KDTBE5_Java_Assignment3.me.practice.Practice01.AuthMethod;
+import KDTBE5_Java_Assignment3.me.practice.Practice01.Company;
+import KDTBE5_Java_Assignment3.me.practice.Practice01.Electronic;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import java.util.Objects;
+
+public class Electronics {
+    private static final Electronics INSTANCE = new Electronics();
+
+    public Electronics() {
+    }
+
+    public static Electronics getINSTANCE() {
+        return INSTANCE;
+    }
+
+    private Electronic[] electronicList;
+
+    public Electronic[] getElectronicList() {
+        return electronicList;
+    }
+
+    public void setElectronicList(Electronic[] electronicList) {
+        this.electronicList = electronicList;
+    }
+
+    @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(INSTANCE, that.INSTANCE) && Arrays.equals(electronicList, that.electronicList);
+    }
+
+    @Override
+    public int hashCode() {
+        int result = Objects.hash(INSTANCE);
+        result = 31 * result + Arrays.hashCode(electronicList);
+        return result;
+    }
+
+    @Override
+    public String toString() {
+        return "Electronics{" +
+                "INSTANCE=" + INSTANCE +
+                ", electronicList=" + Arrays.toString(electronicList) +
+                '}';
+    }
+
+    public Electronic findByProductNo(String productNo) throws Exception {
+        for (Electronic electronic:this.electronicList
+             ) {
+            if(electronic.getProductNo().equals(productNo))return electronic;
+        }
+        throw new Exception("해당 생산번호를 가지는 기기는 없습니다.");
+    };
+
+    public Electronic[] groupByCompanyName(Company company){
+        List<Electronic> electronics = new ArrayList<Electronic>();
+        for (Electronic electronic:this.electronicList
+        ) {
+            if(electronic.getCompany() == company){
+                electronics.add(electronic);
+        }
+        }
+        return electronics.toArray(new Electronic[electronics.size()]);
+    };
+
+    public Electronic[] groupByAuthMethod(AuthMethod authMethod){
+        List<Electronic> electronics = new ArrayList<Electronic>();
+        for (Electronic electronic:this.electronicList
+        ) {
+            if(Arrays.asList(electronic.getAuthMethod()).indexOf(authMethod)>-1){
+                electronics.add(electronic);
+            }
+        }
+        return electronics.toArray(new Electronic[electronics.size()]);
+    };
+}