Java – Python-like list comprehension in Java

javalist-comprehensionmethodsparameterspython

Since Java doesn't allow passing methods as parameters, what trick do you use to implement Python like list comprehension in Java ?

I have a list (ArrayList) of Strings. I need to transform each element by using a function so that I get another list. I have several functions which take a String as input and return another String as output. How do I make a generic method which can be given the list and the function as parameters so that I can get a list back with each element processed. It is not possible in the literal sense, but what trick should I use ?

The other option is to write a new function for each smaller String-processing function which simply loops over the entire list, which is kinda not so cool.

Best Answer

In Java 8 you can use method references:

List<String> list = ...;
list.replaceAll(String::toUpperCase);

Or, if you want to create a new list instance:

List<String> upper = list.stream().map(String::toUpperCase).collect(Collectors.toList());