InetAddressResolver.LookupPolicy (Java SE 21 & JDK 21)
Description: declaration: module: java.base, package: java.net.spi, interface: InetAddressResolver, class: LookupPolicy
Keywords: java.net.spi.InetAddressResolver.LookupPolicy class

Module java.base
Package java.net.spi

# Class InetAddressResolver.LookupPolicy

java.lang.Object
java.net.spi.InetAddressResolver.LookupPolicy

Enclosing interface:
  `InetAddressResolver`

public static final class InetAddressResolver.LookupPolicy extends Object
A `LookupPolicy` object describes characteristics that can be applied to a lookup operation. In particular, it is used to specify the ordering and which filtering should be performed when looking up host addresses.

The default platform-wide lookup policy is constructed by consulting System Properties which affect how IPv4 and IPv6 addresses are returned.

Since:
  18

- ## Field Summary

  Fields
  Modifier and Type
  Field
  Description
  `static final int`
  `IPV4`
  Characteristic value signifying if IPv4 addresses need to be queried during lookup.
  `static final int`
  `IPV4_FIRST`
  Characteristic value signifying if IPv4 addresses should be returned first by `InetAddressResolver`.
  `static final int`
  `IPV6`
  Characteristic value signifying if IPv6 addresses need to be queried during lookup.
  `static final int`
  `IPV6_FIRST`
  Characteristic value signifying if IPv6 addresses should be returned first by `InetAddressResolver`.

- ## Method Summary

  Modifier and Type
  Method
  Description
  `int`
  `characteristics()`
  Returns the set of characteristics of this lookup policy.
  `static InetAddressResolver.LookupPolicy`
  `of(int characteristics)`
  This factory method creates a `LookupPolicy` instance with the given `characteristics` value.

  ### Methods declared in class java.lang.Object

  `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- ## Field Details

  - ### IPV4

    @Native public static final int IPV4
    Characteristic value signifying if IPv4 addresses need to be queried during lookup.
    See Also:
      - Constant Field Values

  - ### IPV6

    @Native public static final int IPV6
    Characteristic value signifying if IPv6 addresses need to be queried during lookup.
    See Also:
      - Constant Field Values

  - ### IPV4_FIRST

    @Native public static final int IPV4_FIRST
    Characteristic value signifying if IPv4 addresses should be returned first by `InetAddressResolver`.
    See Also:
      - Constant Field Values

  - ### IPV6_FIRST

    @Native public static final int IPV6_FIRST
    Characteristic value signifying if IPv6 addresses should be returned first by `InetAddressResolver`.
    See Also:
      - Constant Field Values

- ## Method Details

  - ### of

    public static InetAddressResolver.LookupPolicy of(int characteristics)
    This factory method creates a `LookupPolicy` instance with the given `characteristics` value.

    The `characteristics` value is an integer bit mask which defines parameters of a forward lookup operation. These parameters define at least:

    - the family type of the returned addresses
    - the order in which a resolver implementation should return its results

    To request addresses of specific family types the following bit masks can be combined:

    - `IPV4`: to request IPv4 addresses
    - `IPV6`: to request IPv6 addresses
    It is an error if neither `IPV4` or `IPV6` are set.

    To request a specific ordering of the results:

    - `IPV4_FIRST`: return IPv4 addresses before any IPv6 address
    - `IPV6_FIRST`: return IPv6 addresses before any IPv4 address
    If neither `IPV4_FIRST` or `IPV6_FIRST` are set it implies "system" order of addresses. It is an error to request both `IPV4_FIRST` and `IPV6_FIRST`.
    Parameters:
      `characteristics` - a value which represents the set of lookup characteristics
    Returns:
      an instance of `InetAddressResolver.LookupPolicy`
    Throws:
      `IllegalArgumentException` - if an illegal characteristics bit mask is provided
    See Also:
      - `InetAddressResolver.lookupByName(String, LookupPolicy)`

  - ### characteristics

    public int characteristics()
    Returns the set of characteristics of this lookup policy.
    Returns:
      a characteristics value
    See Also:
      - `InetAddressResolver.lookupByName(String, LookupPolicy)`