optional的orElse 和orElseGet

最新推荐文章于 2025-11-09 14:50:43 发布

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本文深入探讨了Java中Optional类的orElse与orElseGet方法的使用场景及实现原理。详细解释了当Optional对象中存在值时直接返回该值，否则分别返回指定的默认值或通过 Supplier 接口提供的值的机制。

    /**
     * Return the value if present, otherwise return {@code other}.
     *
     * @param other the value to be returned if there is no value present, may
     * be null
     * @return the value, if present, otherwise {@code other}
     */
    public T orElse(T other) {
        return value != null ? value : other;
    }

    /**
     * Return the value if present, otherwise invoke {@code other} and return
     * the result of that invocation.
     *
     * @param other a {@code Supplier} whose result is returned if no value
     * is present
     * @return the value if present otherwise the result of {@code other.get()}
     * @throws NullPointerException if value is not present and {@code other} is
     * null
     */
    public T orElseGet(Supplier<? extends T> other) {
        return value != null ? value : other.get();
    }

orElse 如果value为空则返回other；

orElseGet如果为空则触发other.get()的调用；