How to create a MongoDB query with nested db.runCommand inside a find clause using java driver

Question

I'm using three collections (employee, department and location ) in a mongodb database. I need to list all departments of employee lives in a city starts with "P".

I have created following query using nested db.runCommand which is working fine in mongoDB.

db.Department.find({"id":{ $in: db.runCommand( { 
    // FInd distinct employee
    distinct: "employee", 
    key:"department_id",
    query: {$and:[{ "location_id":{$in: db.runCommand ( { 
        // FInd distinct Location
        distinct: "Location", 
        key:"id",
        query: {"city":{ "$regex": "P.*" }}}).values
        // End - Location       
    }}
    ]}}).values
// End - employee
}}).limit(100)

How to create above query using mongodb-java-driver?