Learn Stream

Question

Someone have a good guide for learn the use of the stream in java or want to explain how to use it?

Answer 1

Stream is awesome tool in Java 8.
You can do numerous things in a single line. Just for an example:

If you have a List of Employee objects and you want a list of firstname+lastname: here is the single line code:

nameList= employeeList.stream().map(e->e.getFirstName()+getLastName()).collect(Collectors.toList());

Explanation:
stream() method of list object returns a stream. map is an "intermediate" method of stream which returns a stream again. In this case it returns a stream of Names (String). There are other intermediate methods like- filter. collect is a terminal method. Which finally makes a list of names out of the stream.

You can play with it many ways. Like if you want the names to be uppercased just insert another map:

nameList= employeeList.stream().map(e->e.getFirstName()+getLastName()).map(s->s.uppercase()).collect(Collectors.toList());

If you want the names which starts with "sen" put a filter:

nameList= employeeList.stream().map(e->e.getFirstName()+getLastName()).filter(s->s.startsWith("sen").collect(Collectors.toList());

Like that. There are infinite possibilities. You can make sum/average in case of numeric data etc.

It is assumed that you have idea of Lambda expression.

Answer 2

yes i have seen it in a video and it is really good for sort or filter the element of a Collection.
i have to exercises more for understand better how to use.
thanks for your reply.

Answer 3

Solo learn should include a Java 8 module for practice. It would be really fun.