*   <li>192.0.2.1
 *   <li>192.0.2.1:80
 *   <li>[2001:db8::1] - {@link #getHost()} omits brackets
 *   <li>[2001:db8::1]:80 - {@link #getHost()} omits brackets
 *   <li>2001:db8::1 - Use {@link #requireBracketsForIPv6()} to prohibit this
 * </ul>
 *
 * <p>Note that this is not an exhaustive list, because these methods are only concerned with
 * brackets, colons, and port numbers. Full validation of the host field (if desired) is the

   *   <li>An IPv6 address string with or without brackets, like {@code [2001:db8::1]} or {@code
   *       2001:db8::1}
   * </ul>
   *
   * @throws IllegalArgumentException if the specifier is not valid.
   */
  public static HostSpecifier fromValid(String specifier) {
    // Verify that no port was specified, and strip optional brackets from
    // IPv6 literals.

    /**
     * Resolves the given host name to an array of IP addresses.
     * The host name is first converted to ASCII using IDN before resolution.
     * IPv6 addresses in bracket notation (e.g., [::1] or [2001:db8::1]) are
     * handled specially by removing the brackets before resolution.
     *
     * @param host the host name to resolve
     * @return an array of IP addresses for the host

        }
    }

    /**
     * Formats an IP address string for use in a URL.
     * IPv6 addresses are wrapped in brackets, IPv4 addresses are returned as-is.
     *
     * @param address the IP address string to format
     * @return the formatted address (IPv6 with brackets, IPv4 unchanged)
     */
    public static String formatForUrl(final String address) {
        if (address == null) {
            return null;

    @Test
    public void testFormatForUrl() {
        // IPv6 addresses - should add brackets
        assertEquals("[::1]", IpAddressUtil.formatForUrl("::1"));
        assertEquals("[2001:db8::1]", IpAddressUtil.formatForUrl("2001:db8::1"));
        assertEquals("[fe80::1]", IpAddressUtil.formatForUrl("fe80::1"));

        // IPv6 addresses already with brackets - should not double-wrap
        assertEquals("[::1]", IpAddressUtil.formatForUrl("[::1]"));

```

### Generic types { #generic-types }

Some types can take "type parameters" in square brackets, to define their internal types, for example a "list of strings" would be declared `list[str]`.

These types that can take type parameters are called **Generic types** or **Generics**.

You can use the same builtin types as generics (with square brackets and types inside):

* `list`
* `tuple`
* `set`
* `dict`

    /**
     * Resolves the given host name to an array of IP addresses.
     * The host name is first converted to ASCII using IDN before resolution.
     * IPv6 addresses in bracket notation (e.g., [::1] or [2001:db8::1]) are
     * handled specially by removing the brackets before resolution.
     *
     * @param host the host name to resolve
     * @return an array of IP addresses for the host

### Headings

- Follow the existing Japanese style: short, descriptive headings (often noun phrases), e.g. 「チェック」.
- Do not add a trailing period at the end of headings.

### Quotes

- Prefer Japanese corner brackets 「」 in normal prose when quoting a term.
- Do not change quotes inside inline code, code blocks, URLs, or file paths.

### Ellipsis

- Keep ellipsis style consistent with existing Japanese docs (commonly `...`).

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