JDK8 Optional 用法记录

Posted 2020-12-19 amberbar

Optional

of 与 ofNullable 的区别

   /**
   * Returns an {@code Optional} with the specified present non-null value.
   *
   * @param <T> the class of the value
   * @param value the value to be present, which must be non-null
   * @return an {@code Optional} with the value present
   * @throws NullPointerException if value is null
   */
  public static <T> Optional<T> of(T value) {
      return new Optional<>(value);
  }

    /**
     * Returns an {@code Optional} describing the specified value, if non-null,
     * otherwise returns an empty {@code Optional}.
     *
     * @param <T> the class of the value
     * @param value the possibly-null value to describe
     * @return an {@code Optional} with a present value if the specified value
     * is non-null, otherwise an empty {@code Optional}
     */
    public static <T> Optional<T> ofNullable(T value) {
        return value == null ? empty() : of(value);
    }

• of 不允许为null
• ofNullable 允许为null