java8 新特性 lambda过滤

1. 定义实体类

package com.atguigu.java8;

public class Employee {

    private int id;
    private String name;
    private int age;
    private double salary;

    public Employee() {
    }

    public Employee(String name) {
        this.name = name;
    }

    public Employee(String name, int age) {
        this.name = name;
        this.age = age;
    }

    public Employee(int id, String name, int age, double salary) {
        this.id = id;
        this.name = name;
        this.age = age;
        this.salary = salary;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    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;
    }

    public double getSalary() {
        return salary;
    }

    public void setSalary(double salary) {
        this.salary = salary;
    }

    public String show() {
        return "测试方法引用！";
    }

    @Override
    public int hashCode() {
        final int prime = 31;
        int result = 1;
        result = prime * result + age;
        result = prime * result + id;
        result = prime * result + ((name == null) ? 0 : name.hashCode());
        long temp;
        temp = Double.doubleToLongBits(salary);
        result = prime * result + (int) (temp ^ (temp >>> 32));
        return result;
    }

    @Override
    public boolean equals(Object obj) {
        if (this == obj)
            return true;
        if (obj == null)
            return false;
        if (getClass() != obj.getClass())
            return false;
        Employee other = (Employee) obj;
        if (age != other.age)
            return false;
        if (id != other.id)
            return false;
        if (name == null) {
            if (other.name != null)
                return false;
        } else if (!name.equals(other.name))
            return false;
        if (Double.doubleToLongBits(salary) != Double.doubleToLongBits(other.salary))
            return false;
        return true;
    }

    @Override
    public String toString() {
        return "Employee [id=" + id + ", name=" + name + ", age=" + age + ", salary=" + salary + "]";
    }

}

2. 测试类

package com.atguigu.java8;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Comparator;
import java.util.List;
import java.util.TreeSet;

import org.junit.Test;

public class TestLambda1 {
   
    List<Employee> emps = Arrays.asList(
            new Employee(101, "张三", 18, 9999.99),
            new Employee(102, "李四", 59, 6666.66),
            new Employee(103, "王五", 28, 3333.33),
            new Employee(104, "赵六", 8, 7777.77),
            new Employee(105, "田七", 38, 5555.55)
    );

    //需求：获取公司中年龄小于 35 的员工信息
    public List<Employee> filterEmployeeAge(List<Employee> emps){
        List<Employee> list = new ArrayList<>();
        
        for (Employee emp : emps) {
            if(emp.getAge() <= 35){
                list.add(emp);
            }
        }
        
        return list;
    }
    
    
    //需求：获取公司中工资大于 5000 的员工信息
    public List<Employee> filterEmployeeSalary(List<Employee> emps){
        List<Employee> list = new ArrayList<>();
        
        for (Employee emp : emps) {
            if(emp.getSalary() >= 5000){
                list.add(emp);
            }
        }
        
        return list;
    }
    
    
    //优化方式四：Stream API
    @Test
    public void test7(){
        emps.stream()
            .filter((e) -> e.getAge() <= 35)
            .forEach(System.out::println);
        
        System.out.println("----------------------------------------------");
        
        emps.stream()
            .map(Employee::getName)
            .limit(3)
            .sorted()
            .forEach(System.out::println);
    }
}