java stream peek的使用

peek用于处理集合中元素（对象）的某个属性的值，但不改变元素（对象）的类型（区别于map操作），举例如下：

package listDemo;

import org.apache.commons.lang3.StringUtils;

import java.util.ArrayList;
import java.util.List;
import java.util.stream.Collectors;

public class StreamPeekDemo {

    public static void main(String[] args) {

        List<Person> personList = new ArrayList<>();
        personList.add(new Person("xiaozhang", 20));
        personList.add(new Person("xiaowang", 21));

        List<Person> peekedList = personList.stream().peek(e -> e.setCity("beijing")).collect(Collectors.toList());
        System.out.println(StringUtils.join(peekedList, "-"));

    }
}

package listDemo;

import lombok.Data;
import lombok.NonNull;
import lombok.RequiredArgsConstructor;

@Data
@RequiredArgsConstructor
public class Person {

    @NonNull
    private String name;
    @NonNull
    private int age;
    private String city;

}

运行结果如下：

Person(name=xiaozhang, age=20, city=beijing)-Person(name=xiaowang, age=21, city=beijing)