如何根据“城市筛选列表”筛选员工列表，并使用java 8维护筛选顺序

Question

如何根据“城市筛选列表”筛选员工列表，并使用java 8维护筛选顺序。

我希望根据另一个列表( filterList : referring )筛选Employee (FilterList)对象，并创建新列表(List2)，并使用Java8维护hte filterList城市订单。

重要注意事项:这里的新列表应该与filterList(城市名称)的顺序相同。

投入：

List<Employee> list1 = Stream.of(
                        new Employee("100","Boston","Massachusetts"),
                        new Employee("400","Atlanta","Georgia"),
                        new Employee("300","pleasanton","California"),
                        new Employee("200","Decatur","Texas"),
                        new Employee("500","Cumming","Atlanta"),
                        new Employee("98","sula","Maine"),
                        new Employee("156","Duluth","Ohio"))
                .collect(Collectors.toList());

过滤列表：

List<String> filterList = Stream.of("pleasanton", "Atlanta", "Cumming", "Boston").collect(Collectors.toList());

预期产出：

List<Employee> list2 = Stream.of(
                        new Employee("300","pleasanton","California"),
                        new Employee("400","Atlanta","Georgia"),
                        new Employee("500","Cumming","Atlanta"),
                        new Employee("100","Boston","Massachusetts"))
                .collect(Collectors.toList());

Answer 1

试试这个：

import java.util.*;
import java.util.stream.*;
class Employee {
    private String salary;
    private String city;
    private String state;
    
    public Employee(String salary, String city, String state) {
        this.salary = salary;
        this.city = city;
        this.state = state;
    }
    
    public String getSalary() {
        return salary;
    }
    
    public String getCity() {
        return city;
    }
    
    public String getState() {
        return state;
    }
}

public class Main {
    public static void main(String[] args) {
        List<Employee> list1 = Stream.of(
                        new Employee("100","Boston","Massachusetts"),
                        new Employee("400","Atlanta","Georgia"),
                        new Employee("300","pleasanton","California"),
                        new Employee("200","Decatur","Texas"),
                        new Employee("500","Cumming","Atlanta"),
                        new Employee("98","sula","Maine"),
                        new Employee("156","Duluth","Ohio"))
                .collect(Collectors.toList());
        
        List<String> filterList = Stream.of("pleasanton", "Atlanta", "Cumming", "Boston").collect(Collectors.toList());
        
        List<Employee> list2 = list1.stream().filter(e -> filterList.contains(e.getCity())).sorted((a, b) -> filterList.indexOf(a.getCity()) - filterList.indexOf(b.getCity())).collect(Collectors.toList());
    list2.stream().forEach(e -> {
                System.out.println("City " + e.getCity());
                System.out.println("State " + e.getState());
                System.out.println("Salary " + e.getSalary());
                System.out.println();
        });
    }
}

Answer 2

与使用indexOf进行比较不同，我们可以使用Comparator.comparingInt：

class Main {
public static void main(String[] args) {
    List<Employee> list = Stream.of(new Employee("100", "Boston", "Massachusetts"),
                    new Employee("400", "Atlanta", "Georgia"),
                    new Employee("300", "pleasanton", "California"),
                    new Employee("200", "Decatur", "Texas"),
                    new Employee("500", "Cumming", "Atlanta"),
                    new Employee("98", "sula", "Maine"),
                    new Employee("156", "Duluth", "Ohio"))
            .collect(Collectors.toList());
    List<String> filterList = Stream.of("pleasanton", "Atlanta", "Cumming", "Boston").collect(Collectors.toList());
    List<Employee> collect = list.stream().filter(re -> filterList.contains(re.getCity())).sorted(Comparator.comparingInt(a -> filterList.indexOf(a.getCity()))).collect(Collectors.toList());
    collect.stream()
            .forEach(e->{
                System.out.println("City" + e.getCity());
                System.out.println("State " + e.getState());
                System.out.println("Salary " + e.getSalary());
                System.out.println();
            });
}

}