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50 lines (39 loc) · 1.62 KB
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package com.jcfc.optional;
import com.jcfc.lambda.entity.Employee;
import org.junit.Test;
import java.util.Optional;
/**
* Optional 容器类的常用方法：
* Optional.of(T t) ：创建一个Optional实例
* Optional.empty() ：创建一个空的Optional实例
* Optional.ofNullable(T t) ：若t不为null，创建Optional实例，否则创建空实例（null）
*
* isPresent() ：判断容器是否包含值
* orElse(T t) ：如果调用的容器对象包含值，则返回该值，否则返回t
* orElseGet(Supplier s) ：如果调用对象包含值，返回该值，否则返回s 获取的值
* map(Function f) ：如果有值对其处理，并返回处理后的Optional，否则返回Optional.empty()
* flatMap(Function mapper) ：与map类似，要求function的返回值必须是Optional
*
*
*/
public class TestOptional {
@Test
public void test() {
Optional<Employee> op = Optional.ofNullable(null);
if (op.isPresent()) {
System.out.println(op.get());
}
Employee employee = op.orElse(new Employee("张三", 18, 888.88, Employee.Status.FREE));
System.out.println(employee);
Employee employee1 = op.orElseGet(() -> new Employee());
System.out.println(employee1);
}
@Test
public void test2() {
Optional<Employee> op = Optional.ofNullable(new Employee("张三", 18, 888.88, Employee.Status.FREE));
Optional<String> str = op.map((Employee::getName));
System.out.println(str.get());
Optional<String> str2 = op.flatMap((e) -> Optional.of(e.getName()));
System.out.println(str2.get());
}
}