问com.sun.net.ssl.internal.www.protocol.https.HttpsURLConnectionOldImpl不能转换为javax.net.ssl.HttpsURLConnection

EN

import java.io.IOException;
import java.net.URL;
import javax.net.ssl.HttpsURLConnection;

public class JavaApplication148 {
    public static void main(String[] args) throws IOException {
        URL url = new URL("https://redmine.ackee.cz/time_entries.xml");
        HttpsURLConnection httpCon = (HttpsURLConnection) url.openConnection();
    }
}

java.lang.ClassCastException: com.sun.net.ssl.internal.www.protocol.https.HttpsURLConnectionOldImpl 
cannot be cast to javax.net.ssl.HttpsURLConnection

package cz.ackee.redmine.commands;

import java.io.IOException;
import java.net.URL;
import javax.net.ssl.HttpsURLConnection;

public abstract class RedmineCommand {      
    public void write(String xmlAddress, String text, String requestMethod) throws IOException{         
         URL url = new URL("https://redmine.xxx.cz/time_entries.xml");
         HttpsURLConnection httpCon = (HttpsURLConnection) url.openConnection(); //this line throws exception
    }       
}

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>cz.ackee</groupId>
    <artifactId>pan-unicorn-bot</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>Pan Unicorn Bot</name>
    <description>Pan unicorn IRC Bot</description>

  <repositories>
  <repository>
    <id>apache-snapshots</id>
    <url>http://repository.apache.org/snapshots/</url>
  </repository>
  </repositories>

    <dependencies>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.30</version>
        </dependency>

        <dependency>
            <groupId>org.hibernate</groupId>
            <artifactId>hibernate-core</artifactId>
            <version>4.3.5.Final</version>
        </dependency>

        <dependency>
            <groupId>org.apache.commons</groupId>
            <artifactId>commons-cli</artifactId>
            <version>1.3-SNAPSHOT</version>
        </dependency>

        <dependency>
            <groupId>com.taskadapter</groupId>
            <artifactId>redmine-java-api</artifactId>
            <version>1.23</version>
        </dependency>
    </dependencies>

  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
  </properties>

    <build>
        <plugins>
            <plugin>
                <artifactId>maven-compiler-plugin</artifactId>
                <groupId>org.apache.maven.plugins</groupId>
                <version>2.3</version>
                <configuration>
                    <source>1.7</source>
                    <target>1.7</target>
                    <downloadSources>true</downloadSources>
                    <downloadJavadocs>true</downloadJavadocs>
                </configuration>
            </plugin>

            <plugin>
                <artifactId>maven-assembly-plugin</artifactId>
                <version>2.2.1</version>
                <configuration>
                    <descriptors>
                        <descriptor>/src/main/assembly/binary.xml</descriptor>
                    </descriptors>
                </configuration>
                <executions>
                    <execution>
                        <id>make-assembly</id>
                        <phase>package</phase>
                        <goals>
                            <goal>single</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-jar-plugin</artifactId>
                <version>2.3.2</version>
                <configuration>
                    <archive>
                        <index>true</index>
                        <manifest>
                            <addClasspath>true</addClasspath>
                            <mainClass>cz.ackee.unicorn.PanUnicornMain</mainClass>
                        </manifest>
                        <manifestEntries>
                            <mode>development</mode>
                            <url>${project.url}</url>
                            <key>value</key>
                        </manifestEntries>
                    </archive>
                </configuration>

            </plugin>
        </plugins>
    </build>

</project>