Java8之lambda

Java8之lambda

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(matched);
 
        //找出工资最高
        Optional hightestSalary = employeeList.stream().max((e1,e2)->Integer.compare(e1.getSalary(),e2.getSalary()));
        System.out.println(hightestSalary);
 
        //返回姓名列表
        List names = employeeList.stream().map(employee -> employee.getName()).collect(Collectors.toList());
        System.out.println(names);
 
        //List转换成Map
        Map employeeMap = employeeList.stream().collect(Collectors.toMap((key->key.getName()),(value->value)));
        employeeMap.forEach((key,value)-> System.out.println(key + "=" + value));
 
        //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(officeCount);
 
        //List转换为Set
        Set officeSet = employeeList.stream().map(employee -> employee.getOffice()).distinct().collect(Collectors.toSet());
        System.out.println(officeSet);
 
        //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(allMatchedEmployees);
 
        //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(sortEmployeeList);
        System.out.println("按照名字的升序列出员工信息:" + sortEmployeeByName);
 
        //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(top2EmployeeList);
 
        //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);
 
    }

 
public class EmployeeTest {
 
    public static List generateData() {
        return Arrays.asList(new Employee("Matt", 5000, "New York"),
                new Employee("Steve", 6000, "London"),
                new Employee("Carrie", 10000, "New York"),
                new Employee("Peter", 7000, "New York"),
                new Employee("Alec", 6000, "London"),
                new Employee("Sarah", 8000, "London"),
                new Employee("Rebecca", 4000, "New York"),
                new Employee("Pat", 20000, "New York"),
                new Employee("Tammy", 9000, "New York"),
                new Employee("Fred", 15000, "Tokyo"));
    }
 
    public static Map generateMapData() {
        Map items = Maps.newHashMap();
        items.put("A", 10);
        items.put("B", 20);
        items.put("C", 30);
        items.put("D", 40);
        items.put("E", 50);
        items.put("F", 60);
 
        return items;
    }
 
 
    @Test
    public void testEmployee() {
        List results = generateData();
 
        //打印出名字是Steve的员工信息
        results.forEach(c -> {
            if (c.getName().equals("Steve")) {
                System.out.println(c);
            }
        });
 
        System.out.println("---------");
 
        //找出年薪超过6000的员工
        results.stream().filter(c -> c.getSalary() >= 60000).forEach(c -> System.out.println(c));
 
        System.out.println("--->>>>>>----");
 
        //java8遍历map
        Map map_ = generateMapData();
        map_.forEach((key, value) -> System.out.println("key:" + key + "," + "value:" + value));
 
        System.out.println("---->>>>分组>>>-----");
 
        //java8 分组 *** 作
        Map> groupMap = results.stream().collect(Collectors.groupingBy(c -> c.getOffice()));
        System.out.println(groupMap);
 
        System.out.println("---->>>>List转化为Map>>>----");
        //List转化Map
        Map map = results.stream().collect(Collectors.toMap(Employee::getName, Employee::getOffice));
        map.forEach((key, value) -> System.out.println("key:" + key + "," + "value:" + value));
 
        System.out.println("---->>>>>>>----");
        Map employeeMap = results.stream().collect(Collectors.toMap((key -> key.getSalary()), (value -> value)));
        employeeMap.forEach((key, value) -> System.out.println(key + "," + value));
 
        System.out.println("---->>遍历map>>>----");
        //打印出值大于30的map
        Map resultMap = map_.entrySet().stream().filter(c -> c.getValue() > 30).collect(Collectors.toMap(p -> p.getKey(), p -> p.getValue()));
        resultMap.forEach((key, value) -> System.out.println(key + "=" + value));
 
        System.out.println(">>>>>>>>>>>>>>>");
        //打印key=D的map
        Map mapResults = map_.entrySet().stream().filter(c -> c.getKey().equals("D")).collect(Collectors.toMap(p -> p.getKey(), p -> p.getValue()));
        mapResults.forEach((key, value) -> System.out.println(key + ">>>>" + value));
 
        System.out.println(">>>>>>>Optional>>>>>>>");
        Optional optional = Optional.of("hello");
        System.out.println(optional.isPresent());
 
    }
 
    @Test
    public void testEmployeeExample() {
        //anyMatch
        List employeeList = generateData();
        boolean isMatch = employeeList.stream().anyMatch(employee -> employee.getOffice().equals("London"));
        System.out.println(isMatch);
 
        //allMatch
        boolean matched = employeeList.stream().allMatch(employee -> employee.getOffice().equals("London"));
        System.out.println(matched);
 
        //找出工资最高的
        Optional employeeOptional = employeeList.stream().max((e1,e2)->Integer.compare(e1.getSalary(),e2.getSalary()));
        System.out.println(employeeOptional);
 
        //找出工资最少的
        Optional employee = employeeList.stream().min((e1,e2)->Integer.compare(e1.getSalary(),e2.getSalary()));
        System.out.println(employee);
 
        //返回姓名列表
        List names = employeeList.stream().map(c->c.getName()).collect(Collectors.toList());
        System.out.println(names);
 
        System.out.println(">>>>>>>>>>>");
        //List转化Map
        Map employeeMap = employeeList.stream().collect(Collectors.toMap((key->key.getName()),(value->value)));
        employeeMap.forEach((key,value)-> System.out.println(key + "=" + value));
 
        //统计办公室是New York的个数
        long officeCount =  employeeList.stream().filter(c->c.getOffice().equals("New York")).count();
        System.out.println(officeCount);
 
        long salaryCount = employeeList.stream().filter(c->c.getSalary()>60000).count();
        System.out.println(salaryCount);
 
        //List转化为Set
        Set officeSet = employeeList.stream().map(c->c.getOffice()).distinct().collect(Collectors.toSet());
        System.out.println(officeSet);
 
        Set salarySet = employeeList.stream().map(c->c.getSalary()).distinct().collect(Collectors.toSet());
        System.out.println(salarySet);
 
        //查找办公室地点是New York的员工
        Optional optionals = employeeList.stream().filter(c->c.getOffice().equals("New York")).findAny();
        System.out.println(optionals);
 
        System.out.println(">>>>>工资降序排序>>>>>");
        //按照工资的降序来列出员工信息
        List sortSalaryEmployeeList = employeeList.stream().sorted((e1,e2)->Integer.compare(e2.getSalary(),e1.getSalary())).collect(Collectors.toList());
        System.out.println(sortSalaryEmployeeList);
 
        System.out.println(">>>>>姓名升序排序>>>>>");
        List sortNameEmployeeList = employeeList.stream().sorted((e1,e2)->e1.getName().compareTo(e2.getName())).collect(Collectors.toList());
        System.out.println(sortNameEmployeeList);
 
        System.out.println(">>>>获取工资最高的前2条员工信息");
        List dispaly2EmployeeList = employeeList.stream().sorted((e1,e2)->Integer.compare(e2.getSalary(),e1.getSalary())).limit(2).collect(Collectors.toList());
        System.out.println(dispaly2EmployeeList);
 
        System.out.println(">>>>获取平均工资");
        OptionalDouble averageSalary = employeeList.stream().mapToInt(c->c.getSalary()).average();
        System.out.println(averageSalary);
 
        System.out.println(">>>>获取工作地点的平均工资");
        OptionalDouble optionalDouble = employeeList.stream().filter(c->c.getOffice().equals("New York")).mapToInt(c->c.getSalary()).average();
        System.out.println(optionalDouble);
 
        System.out.println(">>>>>>Java8 Optional用法>>>>>>");
        Optional stringOptional = Optional.of("test");
        System.out.println(stringOptional.get());
 
        Optional isOptional = Optional.ofNullable("hello");
        System.out.println(isOptional.isPresent());
        System.out.println(isOptional.get());
        System.out.println(isOptional.orElse("0"));
 
        System.out.println(">>>>>>>>>>>>");
        //Optional optionalVal = Optional.of(null);
        // System.out.println(optionalVal);
        Optional optional = Optional.ofNullable("optional");
        System.out.println(optional);
        System.out.println(optional.isPresent());
        System.out.println(optional.get());
        System.out.println(optional.orElse("haha"));
        System.out.println(">>>>>>>>>>>>");
 
        Optional employeeOptional_ = employeeList.stream().filter(c->c.getOffice().equals("New York")).findFirst();
        System.out.println(employeeOptional_);
 
}