Java 9 私有接口方法
Java 9 私有接口方法
在Java 8之前,接口可以支持Constant变量和Abstract方法。因此,我们不能在接口中实现方法,更确切地说,在Java 8之前没有默认实现。看这个例子。
#Live Demo 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(); }
输出
您将看到以下输出。
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
在上面例子中,每个日志方法都有自己的实现。使用Java 8,接口可以支持Constant变量、Abstract方法、Default方法和Static方法。
让我们使用Java 8在接口本身中使用实现默认和静态方法。
#Live Demo 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"); } }
输出
你将看到如下输出:
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
在上面的例子中,我们再次重复。使用Java 9,接口可以支持Constant变量、Abstract方法、Default方法、Static方法、Private方法和Private Static方法。
我们在Java 9中使用私有方法。
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"); } }
输出
你将看到如下输出:
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