Stream系列Map方法使用

Posted 2020-11-22 javaweibiancheng

Stream 将List 里面的对象转换为新的对象 

EmployeeTestCase.java

package com.example.demo;
 
import lombok.Data;
import lombok.ToString;
import lombok.extern.log4j.Log4j2;
import org.junit.Test;
 
import java.util.List;
import java.util.stream.Collectors;
 
@Log4j2
public class EmployeeTestCase extends BaseTest{
 
    @Test
    public void map(){
        //将Employee 转换 Leader 列表
        List<Leader> leaders = list.stream().filter(employee -> employee.getSalary() == 2000).map(employee -> {
            Leader leader = new Leader();
            leader.setName(employee.getName());
            leader.setSalary(employee.getSalary());
            return leader;
        }).peek(System.out::println).collect(Collectors.toList());
    }
    @Data
    @ToString
    class Leader{
        private String name;
        private double salary;
    }
 
}

BaseTest.java

        package com.example.demo;

        import java.util.Arrays;
        import java.util.List;

        public class BaseTest {
            protected static final List<Employee> list = Arrays.asList(
                    new Employee(1, "Alex", 1000),
                    new Employee(2, "Michael", 2000),
                    new Employee(3, "Jack", 1500),
                    new Employee(4, "Owen", 1500),
                    new Employee(5, "Denny", 2000));

            protected static final List<List<Employee>> listFlat = Arrays.asList(
                    Arrays.asList(new Employee(1, "Alex", 1000),
                                  new Employee(2, "Michael", 2000)),
                    Arrays.asList(new Employee(3, "Jack", 1500),
                                  new Employee(4, "Owen", 1500)),
                    Arrays.asList(new Employee(5, "Denny", 2000)));
        }