Java 8 Lambda 根据属性去重

示例

Student 类

public class Student {
    private String name;
    private int age;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }
}

测试类：

import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.function.Function;
import java.util.function.Predicate;

public class DistinctByFieldTest {

    public static void main(String[] args) {
        Student stu1 = new Student();
        stu1.setName("小张");
        stu1.setAge(22);
        Student stu2 = new Student();
        stu2.setName("小张");
        stu2.setAge(25);
        Student stu3 = new Student();
        stu3.setName("小王");
        stu3.setAge(19);
        List<Student> students = new ArrayList();
        students.add(stu1);
        students.add(stu2);
        students.add(stu3);
        System.out.println("去重前:");
        students.stream().forEach(x->System.out.println(x.toString()));
        System.out.println("去重后");
        students.stream().filter(distinctByField(student -> student.getName())).forEach(x->System.out.println(x.toString()));
    }

    /**
     * 根据属性去重
     * @param fieldExtractor
     * @param <T>
     * @return
     */
    public static  <T> Predicate<T> distinctByField(Function<? super T,?> fieldExtractor){
        Map<Object,Boolean> map = new ConcurrentHashMap<>();
        return t -> map.putIfAbsent(fieldExtractor.apply(t), Boolean.TRUE) == null;
    }
}