java8Optional 使用

一、示例

public class TestMain {@Data@NoArgsConstructor@AllArgsConstructor@ToStringpublic static class Leader {private Long employeeId;private BigDecimal bonus;}@Data@NoArgsConstructor@AllArgsConstructor@ToStringpublic static class Employee {private Long id;private String name;private Boolean leader;}public static class FiltUtil {public void OptionalStudy() {Optional<Leader> leader = Optional.ofNullable(getEmployeeById(1L).filter(Employee::getLeader).map(Employee::getId).flatMap(this::getLeaderByEmployeeId).orElse(null));if (leader.isPresent()) {Optional.of(leader.map(Leader::getBonus).map(bonus -> String.format("员工ID为1的leader奖金为：%s", bonus)).orElse("员工ID为1的leader也没有奖金")).ifPresent(System.out::println);} else {System.out.println("员工ID为1的leader未找到，他可能只是一个基层员工，不配拥有奖金");}}private Optional<Employee> getEmployeeById(Long id) {//return Optional.of(new Employee(1L, "大老板", Boolean.TRUE));return Optional.of(new Employee(1L, "大老板", Boolean.FALSE));}private Optional<Leader> getLeaderByEmployeeId(Long employeeId) {//return employeeId == 1L ? Optional.of(new Leader(1L, BigDecimal.valueOf(1000000000))) : Optional.empty();return employeeId == 1L ? Optional.of(new Leader(1L, null)) : Optional.empty();}}public static void main(String[] args) {
//        FiltUtil filtUtil = new FiltUtil();
//        filtUtil.OptionalStudy();Employee employee = new Employee(null,"",true);//Optional.断言
//        Optional.ofNullable(employee.getId()).orElseThrow(()-> new IllegalArgumentException(String.format("%s人员的Id不能为NULL", employee.toString())));Optional.ofNullable(employee).filter(e-> StringUtil.isEmpty(e.getName())).orElseThrow(()-> new IllegalArgumentException(String.format("%s人员的name不能为空", employee.toString())));Optional.ofNullable(employee.getName()).orElseThrow(()-> new IllegalArgumentException(String.format("%s人员的name不能为空", employee.toString())));//Optional.非空判断Optional.ofNullable(employee).ifPresent(o -> o.setName("UNKNOW"));System.out.println(employee.toString());}
}