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Java 9 - Private Interface Methods
Java 9 - Private Interface Methods
Prior to java 8, interfaces can have following type of variables/methods.
Constant variables
Abstract methods
So we cannot have method implementation in interfaces or more precisely a default implementation prior to Java 8. See the example.
pubpc class Tester {
pubpc 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
pubpc void logInfo(String message) {
getConnection();
System.out.println("Log Message : " + "INFO");
closeConnection();
}
@Override
pubpc void logWarn(String message) {
getConnection();
System.out.println("Log Message : " + "WARN");
closeConnection();
}
@Override
pubpc void logError(String message) {
getConnection();
System.out.println("Log Message : " + "ERROR");
closeConnection();
}
@Override
pubpc void logFatal(String message) {
getConnection();
System.out.println("Log Message : " + "FATAL");
closeConnection();
}
@Override
pubpc void getConnection() {
System.out.println("Open Database connection");
}
@Override
pubpc void closeConnection() {
System.out.println("Close Database connection");
}
}
final class LogMySql implements Logging {
@Override
pubpc void logInfo(String message) {
getConnection();
System.out.println("Log Message : " + "INFO");
closeConnection();
}
@Override
pubpc void logWarn(String message) {
getConnection();
System.out.println("Log Message : " + "WARN");
closeConnection();
}
@Override
pubpc void logError(String message) {
getConnection();
System.out.println("Log Message : " + "ERROR");
closeConnection();
}
@Override
pubpc void logFatal(String message) {
getConnection();
System.out.println("Log Message : " + "FATAL");
closeConnection();
}
@Override
pubpc void getConnection() {
System.out.println("Open Database connection");
}
@Override
pubpc 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();
}
Output
You will see the following output.
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
In above example, each log method has its own implementation. With Java 8 interfaces can have following type of variables/methods.
Constant variables
Abstract methods
Default methods
Static methods
Let s have default implementation and static methods in interface itself using Java 8.
pubpc class Tester {
pubpc 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");
}
}
Output
You will see the following output.
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
In above example, we re having repeation again. With Java 9 interfaces can have following type of variables/methods.
Constant variables
Abstract methods
Default methods
Static methods
Private methods
Private Static methods
Let s have private methods and use them in Java 9.
pubpc class Tester {
pubpc 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");
}
}
Output
You will see the following output.
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 connectionAdvertisements