在Java 8之前，接口可以具有以下类型的变量/方法。
- Constant variables (常量)
- Abstract methods (抽象方法)
因此，无涯教程不能在接口中实现方法实现，或更确切地说，不能在Java 8之前拥有默认实现。请参见示例。
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();
}
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
在上面的示例中，每个log方法都有其自己的实现。使用Java 8接口可以具有以下类型的变量/方法。
- Constant variables (常量)
- Abstract methods (抽象方法)
- Default methods (默认方法)
- Static methods (静态方法)
让无涯教程使用Java 8在接口本身中使用默认实现和静态方法。
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";
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");
}
}
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
使用Java 9接口可以具有以下类型的变量/方法。
- Constant variables (常量)
- Abstract methods (抽象方法)
- Default methods (默认方法)
- Static methods (静态方法)
- Private methods (私有方法)
- Private Static methods (私有静态方法)
让无涯教程拥有私有方法，并在Java 9中使用它们。
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");
}
}
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
参考链接
https://www.learnfk.com/java/java9-private-interface-methods.html
标签：教程,String,Database,void,无涯,connection,Message,Java9,Log From： https://blog.51cto.com/u_14033984/8986982