Looks like you are using the Java methods on java.lang.Double:
public final class java.lang.Double : Number, Comparable<Double> {
public func toString() -> String!
public func toString() -> String!
public func toHexString() -> String!
public func valueOf() -> Double!
public static func valueOf(_ arg1: String!) -> Double!
public static func parseDouble(_ arg1: String!) -> Double
public func isNaN() -> Boolean
public func isInfinite() -> Boolean
public func isFinite() -> Boolean
that’s just the way it is, for now. remember that silver. brings the LANGUAGE to java, not the cocoa class libraries. the types you work with are the java and android types, not the cocoa types.