Java 9 - Metode Antarmuka Pribadi

Sebelum Java 8, antarmuka dapat memiliki tipe variabel/metode berikut.

• Variabel konstan
• Metode abstrak

Jadi kita tidak bisa memiliki implementasi metode di antarmuka atau lebih tepatnya implementasi default sebelum Java 8. Lihat contohnya.

Demo Langsung

public class Tester {
   public static void main(String []args) {
      LogOracle log = new LogOracle();
      log.logInfo("");
      log.logWarn("");
      log.logError("");
      log.logFatal("");
      LogMySql log1 = new LogMySql();
      log1.logInfo("");
      log1.logWarn("");
      log1.logError("");
      log1.logFatal("");
   }
}
final class LogOracle implements Logging {
   @Override
   public void logInfo(String message) {
      getConnection();
      System.out.println("Log Message : " + "INFO");
      closeConnection();
   }
   @Override
   public void logWarn(String message) {
      getConnection();
      System.out.println("Log Message : " + "WARN");
      closeConnection();
   }
   @Override
   public void logError(String message) {
      getConnection();
      System.out.println("Log Message : " + "ERROR");
      closeConnection();
   }
   @Override
   public void logFatal(String message) {
      getConnection();
      System.out.println("Log Message : " + "FATAL");
      closeConnection();
   }
   @Override
   public void getConnection() {
      System.out.println("Open Database connection");
   }
   @Override
   public void closeConnection() {
      System.out.println("Close Database connection");
   }
}
final class LogMySql implements Logging {
   @Override
   public void logInfo(String message) {
      getConnection();
      System.out.println("Log Message : " + "INFO");
      closeConnection();
   }
   @Override
   public void logWarn(String message) {
      getConnection();
      System.out.println("Log Message : " + "WARN");
      closeConnection();
   }
   @Override
   public void logError(String message) {
      getConnection();
      System.out.println("Log Message : " + "ERROR");
      closeConnection();
   }
   @Override
   public void logFatal(String message) {
      getConnection();
      System.out.println("Log Message : " + "FATAL");
      closeConnection();
   }
   @Override
   public void getConnection() {
      System.out.println("Open Database connection");
   }
   @Override
   public void closeConnection() {
      System.out.println("Close Database connection");
   }
}
interface Logging {
   String ORACLE = "Oracle_Database";
   String MYSQL = "MySql_Database";

   void logInfo(String message);
   void logWarn(String message);
   void logError(String message);
   void logFatal(String message);

   void getConnection();
   void closeConnection();
}

Keluaran

Anda akan melihat output berikut.

Open Database connection
Log Message : INFO
Close Database connection
Open Database connection
Log Message : WARN
Close Database connection
Open Database connection
Log Message : ERROR
Close Database connection
Open Database connection
Log Message : FATAL
Close Database connection

Dalam contoh di atas, setiap metode log memiliki implementasinya sendiri. Dengan antarmuka Java 8 dapat memiliki jenis variabel/metode berikut.

• Variabel konstan
• Metode abstrak
• Metode default
• Metode statis

Mari kita memiliki implementasi default dan metode statis dalam antarmuka itu sendiri menggunakan Java 8.

Demo Langsung

public class Tester {
   public static void main(String []args) {
      LogOracle log = new LogOracle();
      log.logInfo("");
      log.logWarn("");
      log.logError("");
      log.logFatal("");
      
      LogMySql log1 = new LogMySql();
      log1.logInfo("");
      log1.logWarn("");
      log1.logError("");
      log1.logFatal("");
   }
}
final class LogOracle implements Logging { 
}
final class LogMySql implements Logging { 
}
interface Logging {
   String ORACLE = "Oracle_Database";
   String MYSQL = "MySql_Database";

   default void logInfo(String message) {
      getConnection();
      System.out.println("Log Message : " + "INFO");
      closeConnection();
   }
   default void logWarn(String message) {
      getConnection();
      System.out.println("Log Message : " + "WARN");
      closeConnection();
   }
   default void logError(String message) {
      getConnection();
      System.out.println("Log Message : " + "ERROR");
      closeConnection();
   }
   default void logFatal(String message) {
      getConnection();
      System.out.println("Log Message : " + "FATAL");
      closeConnection();
   }
   static void getConnection() {
      System.out.println("Open Database connection");
   }
   static void closeConnection() {
      System.out.println("Close Database connection");
   }
}

Keluaran

Anda akan melihat output berikut.

Open Database connection
Log Message : INFO
Close Database connection
Open Database connection
Log Message : WARN
Close Database connection
Open Database connection
Log Message : ERROR
Close Database connection
Open Database connection
Log Message : FATAL
Close Database connection

Dalam contoh di atas, kami mengalami pengulangan lagi. Dengan antarmuka Java 9 dapat memiliki jenis variabel/metode berikut.

• Variabel konstan
• Metode abstrak
• Metode default
• Metode statis
• Metode pribadi
• Metode Statis Pribadi

Mari kita memiliki metode pribadi dan menggunakannya di Java 9.

public class Tester {
   public static void main(String []args) {
      LogOracle log = new LogOracle();
      log.logInfo("");
      log.logWarn("");
      log.logError("");
      log.logFatal("");
      
      LogMySql log1 = new LogMySql();
      log1.logInfo("");
      log1.logWarn("");
      log1.logError("");
      log1.logFatal("");
   }
}
final class LogOracle implements Logging { 
}
final class LogMySql implements Logging { 
}
interface Logging {
   String ORACLE = "Oracle_Database";
   String MYSQL = "MySql_Database";

   private void log(String message, String prefix) {
      getConnection();
      System.out.println("Log Message : " + prefix);
      closeConnection();
   }
   default void logInfo(String message) {
      log(message, "INFO");
   }
   default void logWarn(String message) {
      log(message, "WARN");
   }
   default void logError(String message) {
      log(message, "ERROR");
   }
   default void logFatal(String message) {
      log(message, "FATAL");
   }
   private static void getConnection() {
      System.out.println("Open Database connection");
   }
   private static void closeConnection() {
      System.out.println("Close Database connection");
   }
}

Keluaran

Anda akan melihat output berikut.

Open Database connection
Log Message : INFO
Close Database connection
Open Database connection
Log Message : WARN
Close Database connection
Open Database connection
Log Message : ERROR
Close Database connection
Open Database connection
Log Message : FATAL
Close Database connection