java.util.Optional

public static Optional empty()//构建空的Optional
public boolean equals(Object arg0)
public Optional filter(Predicate arg0)//如果arg0返回true，则返回原值，否则返回空的Optional
public Optional flatMap(Function arg0)//转化为另一种类型，arg0中要返回Optional
public Object get()//获取值
public int hashCode()
public void ifPresent(Consumer arg0)//如果值存在则执行
public boolean isPresent()//值是否存在
public Optional map(Function arg0)//转化为另一种类型
public static Optional of(Object arg0)//构建值为arg0的Optional，值为空抛异常
public static Optional ofNullable(Object arg0)//构建值为arg0的Optional，值为空不抛异常
public Object orElse(Object arg0)//如果为空返回默认值
public Object orElseGet(Supplier arg0)//如果为空返回工厂返回的默认值
public Object orElseThrow(Supplier arg0)//如果为空抛异常
public String toString()

 

public static <T> Optional<T> empty()
public Optional<T> filter(Predicate<? super T> arg0)
public <U> Optional<U> flatMap(Function<? super T, Optional<U>> arg0)
public T get()
public void ifPresent(Consumer<? super T> arg0)
public boolean isPresent()
public <U> Optional<U> map(Function<? super T, ? extends U> arg0)
public static <T> Optional<T> of(T arg0)
public static <T> Optional<T> ofNullable(T arg0)
public T orElse(T arg0)
public T orElseGet(Supplier<? extends T> arg0)
public <X> T orElseThrow(Supplier<? extends X> arg0) throws X