Eclipse Projects - Many types in one

How to make an Eclipse project be both PyDev and Java project?

File: .project

<?xml version="1.0" encoding="UTF-8"?>
<projectDescription>
    <name>Project-Name</name>
    <comment></comment>
    <projects>
    </projects>
    <buildSpec>
        <buildCommand>
            <name>org.python.pydev.PyDevBuilder</name>
            <arguments>
            </arguments>
        </buildCommand>
        <buildCommand>
            <name>org.eclipse.jdt.core.javabuilder</name>
            <arguments>
            </arguments>
        </buildCommand>
    </buildSpec>
    <natures>
        <nature>org.python.pydev.pythonNature</nature>
        <nature>org.eclipse.jdt.core.javanature</nature>
    </natures>
</projectDescription>

File: .classpath

<?xml version="1.0" encoding="UTF-8"?>
<classpath>
    <classpathentry kind="src" path="java-src"/>
    <classpathentry kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER"/>
    <classpathentry kind="output" path="classes"/>
</classpath>

File: .pydevproject

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<?eclipse-pydev version="1.0"?>
<pydev_project>
    <pydev_property name="org.python.pydev.PYTHON_PROJECT_INTERPRETER">Default</pydev_property>
    <pydev_property name="org.python.pydev.PYTHON_PROJECT_VERSION">python 2.7</pydev_property>
    <pydev_pathproperty name="org.python.pydev.PROJECT_SOURCE_PATH">
        <path>/Project-Name/src</path>
    </pydev_pathproperty>
</pydev_project>