Java8流函数方法测试小结 Java8流函数方法测试小结

最近用到 Java8 新特性时候，发现流函数非常好用，特地总结了一下常用的方法和应用范围，下面通过一个例子来展示
1、实体类代码

package com.test; import lombok.AllArgsConstructor; import lombok.Builder; import lombok.Data; import lombok.NoArgsConstructor; /** * Author:LSR * Date:2020/4/30 * DESCRIPTION: */public class Employee {private String name; private int salary; private String office; public String getName() { return name; }public void setName(String name) { this.name = name; }public int getSalary() { return salary; }public void setSalary(int salary) { this.salary = salary; }public String getOffice() { return office; }public void setOffice(String office) { this.office = office; }public Employee(String name, int salary, String office) { this.name = name; this.salary = salary; this.office = office; }@Override public String toString() { return "Employee{" + "name='" + name + '\'' + ", salary=" + salary + ", office='" + office + '\'' + '}'; } }

【Java8流函数方法测试小结】2、Java8 流函数各种方法应用测试代码

package com.test; import java.util.*; import java.util.stream.Collectors; public class Java8Test2 { private static List employeeList = new ArrayList<>(); static{ employeeList.add(new Employee("Matt",5000,"New York")); employeeList.add(new Employee("Steve",6000,"London")); employeeList.add(new Employee("Carrie",20000,"New York")); employeeList.add(new Employee("Peter",7000,"New York")); employeeList.add(new Employee("Pat",8000,"London")); employeeList.add(new Employee("Tammy",29000,"Shanghai")); /*employeeList.add(Employee.builder().name("Matt").salary(5000).office("New York").build()); employeeList.add(Employee.builder().name("Steve").salary(6000).office("London").build()); employeeList.add(Employee.builder().name("Carrie").salary(20000).office("New York").build()); employeeList.add(Employee.builder().name("Peter").salary(7000).office("New York").build()); employeeList.add(Employee.builder().name("Pat").salary(8000).office("London").build()); employeeList.add(Employee.builder().name("Tammy").salary(29000).office("Shanghai").build()); */ }public static void main(String[] args) { //anyMatch boolean isMatch = employeeList.stream().anyMatch(employee -> employee.getOffice().equals("London")); System.out.println(isMatch); //返回所有salary大于6000 boolean matched = employeeList.stream().allMatch(employee -> employee.getSalary()>4000); System.out.println("返回所有salary大于6000:"+matched); //找出工资最高 Optional hightestSalary = employeeList.stream().max((e1, e2)->Integer.compare(e1.getSalary(),e2.getSalary())); System.out.println("找出工资最高:"+hightestSalary); //返回姓名列表 List names = employeeList.stream().map(employee -> employee.getName()).collect(Collectors.toList()); System.out.println("返回姓名列表:"+names); //List转换成Map 其中 (k1, k2)->k2 表示最后的值覆盖前面的值可以达到去重目的 Map employeeMap = employeeList.stream().collect(Collectors.toMap((key->key.getName()),(value->value),(k1, k2)->k2)); employeeMap.forEach((key,value)-> System.out.println(key + "=" + value.toString())); //统计办公室是New York的个数 long officeCount = employeeList.stream().filter(employee -> employee.getOffice().equals("Shanghai")).count(); System.out.println("统计办公室是New York的个数:"+officeCount); //List转换为Set Set officeSet = employeeList.stream().map(employee -> employee.getOffice()).distinct().collect(Collectors.toSet()); System.out.println("List转换为Set:"+officeSet.toString()); //查找办公室地点是New York的员工 Optional allMatchedEmployees = employeeList.stream().filter(employee -> employee.getOffice().equals("New York")).findAny(); System.out.println("查找办公室地点是New York的员工:"+allMatchedEmployees.toString()); //按照工资的降序来列出员工信息 List sortEmployeeList =employeeList.stream().sorted((e1,e2)->Integer.compare(e2.getSalary(),e1.getSalary())).collect(Collectors.toList()); //按照名字的升序列出员工信息 List sortEmployeeByName = employeeList.stream().sorted((e1,e2)->e1.getName().compareTo(e2.getName())).collect(Collectors.toList()); System.out.println("按照工资的降序来列出员工信息:" +sortEmployeeList); System.out.println("按照名字的升序列出员工信息:" + sortEmployeeByName.toString()); //获取工资最高的前2条员工信息 List top2EmployeeList= employeeList.stream() .sorted((e1,e2)->Integer.compare(e2.getSalary(),e1.getSalary())) .limit(2) .collect(Collectors.toList()); System.out.println("获取工资最高的前2条员工信息:"+top2EmployeeList.toString()); //获取平均工资 OptionalDouble averageSalary = employeeList.stream().mapToInt(employee->employee.getSalary()).average(); System.out.println("平均工资:" + averageSalary); //查找New York OptionalDouble averageSalaryByOffice = employeeList.stream().filter(employee -> employee.getOffice() .equals("New York")) .mapToInt(employee->employee.getSalary()) .average(); System.out.println("New York办公室平均工资:" + averageSalaryByOffice); } }