Stream foreach Java 8 中的递增计数器
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Incrementing counter in Stream foreach Java 8
提问by Damien-Amen
I'd like to increment a counterwhich is an AtomicIntegeras I loop through using foreach
我想增加一个counter是一个AtomicInteger，因为我通过循环使用foreach
public class ConstructorTest {
public static void main(String[] args) {
AtomicInteger counter = new AtomicInteger(0);
List<Foo> fooList = Collections.synchronizedList(new ArrayList<Foo>());
List<String> userList = Collections.synchronizedList(new ArrayList<String>());
userList.add("username1_id1");
userList.add("username2_id2");
userList.stream().map(user -> new Foo(getName(user), getId(user))).forEach(fooList::add);
//how do I increment the counter in the above loop
fooList.forEach(user -> System.out.println(user.getName() + " " + user.getId()));
}
private static String getName(String user) {
return user.split("_")[0];
}
private static String getId(String user) {
return user.split("_")[1];
}
}
采纳答案by bradimus
Depends on where you want to increment.
取决于您要增加的位置。
Either
任何一个
userList.stream()
.map(user -> {
counter.getAndIncrement();
return new Foo(getName(user), getId(user));
})
.forEach(fooList::add);
or
或者
userList.stream()
.map(user -> new Foo(getName(user), getId(user)))
.forEach(foo -> {
fooList.add(foo);
counter.getAndIncrement();
});
回答by OldCurmudgeon
You can change it to an anonymous class:
您可以将其更改为匿名类：
userList.stream().map(new Function<String, Object>() {
@Override
public Object apply(String user) {
counter.addAndGet(1);
return new Foo(getName(user), getId(user));
}
}).forEach(fooList::add);
Remember to make counterfinal.
记得做counterfinal。
回答by SIVA KUMAR
can also be done using Stream.peek()
也可以使用 Stream.peek() 完成
userList.stream()
.map(user -> new Foo(getName(user), getId(user)))
.peek(u -> counter.getAndIncrement())
.forEach(fooList::add);
回答by Tiago Medici
how about using
怎么样使用
java.util.concurrent.atomic.AtomicInteger
example:
例子：
AtomicInteger index = new AtomicInteger();
actionList.forEach(action -> {
index.getAndIncrement();
});
