src/main/java/io/reactivex/internal/functions/Functions.java
public static <T> Callable<T> justCallable(T value) {
        return new JustValue<Object, T>(value);
    }
public static <T> Callable<T> justCallable(T value) {
        return new JustValue<Object, T>(value);
    }
Returns a Callable that returns the given value.
@param <T> the value type
@param value the value to return
@return the new Callable instance