Is there a java 8 way of doing the following?
for(int i;i<=100;i++){
Person person=new Person();
person.setId(i);
person.setName("name"+i);
list.add(person)
}
2 Answers
You can obtain a list of persons by mapping each int from 0 to 100 into a Person.
List<Person> persons = IntStream.rangeClosed(0, 100).mapToObj(i -> {
Person person = new Person();
person.setId(i);
person.setName("name" + i);
return person;
}).collect(Collectors.toList());
Then, you can append that persons list into an existing one for example.
IntStream.rangeClosed return a IntStream of primitive int. Each is mapped to the object Person with mapToObj and collected into a list with Collectors.toList().
It would be cleaner if you had a constructor of Person taking the id and the name. With such a constructor, you could write:
List<Person> persons = IntStream.rangeClosed(0, 100)
.mapToObj(i -> new Person(i, "name" + i))
.collect(Collectors.toList());
Comments
Yes:
IntStream.rangeClosed(0, 100)
.forEach(i -> {
Person person=new Person();
person.setId(i);
person.setName("name"+i);
list.add(person);
});
EDIT:
As commented below, accessing an existing list inside the lambda expression parameter of the stream operation goes against functional programming. It's better to do:
List<Person> persons = IntStream.rangeClosed(0, 100)
.mapToObj(i -> {
Person person=new Person();
person.setId(i);
person.setName("name" + i);
return person;
})
.collect(Collectors.toList());
See https://docs.oracle.com/javase/8/docs/api/java/util/stream/IntStream.html.
4 Comments
Tunaki
This doesn't compile. And using
forEach is probably not a good idea: it is discouraged to use it in such cases. For example, if you run it in parallel, you would be surprised at the result.
user68883
yes it doesn't compile with foreach, I tried editing the answer but could not . Any specific drawbacks of using forEach ?
M A
Apologies as I don't have access to a compiler right now... @Tunaki is right. You should avoid stateful lambdas especially when doing parallel stuff. This simple approach may only be accepted if the stream operation is serial.
Brian Goetz
This works, but using a stream in this way offers no benefit over the for loop. Streams are cool, but that doesn't mean we should replace all loops with streams.
new Person(id, name)exist?