AlgorithmParameters

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## java.security
Class AlgorithmParameters

    java.lang.Object
      java.security.AlgorithmParameters

    public class AlgorithmParameters

extends Object

This class is used as an opaque representation of cryptographic parameters.

An `AlgorithmParameters` object for managing the parameters for a particular algorithm can be obtained by calling one of the `getInstance` factory methods (static methods that return instances of a given class).

There are two ways to request such an implementation: by specifying either just an algorithm name, or both an algorithm name and a package provider.

- If just an algorithm name is specified, the system will determine if there is an AlgorithmParameters implementation for the algorithm requested available in the environment, and if there is more than one, if there is a preferred one.
- If both an algorithm name and a package provider are specified, the system will determine if there is an implementation in the package requested, and throw an exception if there is not.

Once an `AlgorithmParameters` object is returned, it must be initialized via a call to `init`, using an appropriate parameter specification or parameter encoding.

A transparent parameter specification is obtained from an `AlgorithmParameters` object via a call to `getParameterSpec`, and a byte encoding of the parameters is obtained via a call to `getEncoded`.

Since:
  1.2
Version:
  1.19, 02/02/00
Author:
  Jan Luehe
See Also:
  `AlgorithmParameterSpec`, `DSAParameterSpec`, `KeyPairGenerator`

Method Summary
`String` | `getAlgorithm()` Returns the name of the algorithm associated with this parameter object.
`byte[]` | `getEncoded()` Returns the parameters in their primary encoding format.
`byte[]` | `getEncoded(String format)` Returns the parameters encoded in the specified scheme.
`static AlgorithmParameters` | `getInstance(String algorithm)` Generates a parameter object for the specified algorithm.
`static AlgorithmParameters` | `getInstance(String algorithm, Provider provider)` Generates a parameter object for the specified algorithm, as supplied by the specified provider, if such an algorithm is available from the provider.
`static AlgorithmParameters` | `getInstance(String algorithm, String provider)` Generates a parameter object for the specified algorithm, as supplied by the specified provider, if such an algorithm is available from the provider.
`AlgorithmParameterSpec` | `getParameterSpec(Class paramSpec)` Returns a (transparent) specification of this parameter object.
`Provider` | `getProvider()` Returns the provider of this parameter object.
`void` | `init(AlgorithmParameterSpec paramSpec)` Initializes this parameter object using the parameters specified in `paramSpec`.
`void` | `init(byte[] params)` Imports the specified parameters and decodes them according to the primary decoding format for parameters.
`void` | `init(byte[] params, String format)` Imports the parameters from `params` and decodes them according to the specified decoding scheme.
`String` | `toString()` Returns a formatted string describing the parameters.

Methods inherited from class java.lang.Object
`equals, getClass, hashCode, notify, notifyAll, wait, wait, wait`

Method Detail

### getAlgorithm

    public final String getAlgorithm()

  Returns the name of the algorithm associated with this parameter object.

  Returns:
    the algorithm name.

### getInstance

    public static AlgorithmParameters getInstance(String algorithm)
                                           throws NoSuchAlgorithmException

  Generates a parameter object for the specified algorithm.

  If the default provider package provides an implementation of the requested algorithm, an instance of AlgorithmParameters containing that implementation is returned. If the algorithm is not available in the default package, other packages are searched.

  The returned parameter object must be initialized via a call to `init`, using an appropriate parameter specification or parameter encoding.

  Parameters:
    `algorithm` - the name of the algorithm requested.
  Returns:
    the new parameter object.
  Throws:
    `NoSuchAlgorithmException` - if the algorithm is not available in the environment.

### getInstance

    public static AlgorithmParameters getInstance(String algorithm,
                                                  String provider)
                                           throws NoSuchAlgorithmException,
                                                  NoSuchProviderException

  Generates a parameter object for the specified algorithm, as supplied by the specified provider, if such an algorithm is available from the provider.

  The returned parameter object must be initialized via a call to `init`, using an appropriate parameter specification or parameter encoding.

  Parameters:
    `algorithm` - the name of the algorithm requested.
    `provider` - the name of the provider.
  Returns:
    the new parameter object.
  Throws:
    `NoSuchAlgorithmException` - if the algorithm is not available in the package supplied by the requested provider.
    `NoSuchProviderException` - if the provider is not available in the environment.
    `IllegalArgumentException` - if the provider name is null or empty.
  See Also:
    `Provider`

### getInstance

    public static AlgorithmParameters getInstance(String algorithm,
                                                  Provider provider)
                                           throws NoSuchAlgorithmException

  Generates a parameter object for the specified algorithm, as supplied by the specified provider, if such an algorithm is available from the provider. Note: the `provider` doesn't have to be registered.

  The returned parameter object must be initialized via a call to `init`, using an appropriate parameter specification or parameter encoding.

  Parameters:
    `algorithm` - the name of the algorithm requested.
    `provider` - the name of the provider.
  Returns:
    the new parameter object.
  Throws:
    `NoSuchAlgorithmException` - if the algorithm is not available in the package supplied by the requested provider.
    `IllegalArgumentException` - if the `provider` is null.
  Since:
    1.4
  See Also:
    `Provider`

### getProvider

    public final Provider getProvider()

  Returns the provider of this parameter object.

  Returns:
    the provider of this parameter object

### init

    public final void init(AlgorithmParameterSpec paramSpec)
                    throws InvalidParameterSpecException

  Initializes this parameter object using the parameters specified in `paramSpec`.

  Parameters:
    `paramSpec` - the parameter specification.
  Throws:
    `InvalidParameterSpecException` - if the given parameter specification is inappropriate for the initialization of this parameter object, or if this parameter object has already been initialized.

### init

    public final void init(byte[] params)
                    throws IOException

  Imports the specified parameters and decodes them according to the primary decoding format for parameters. The primary decoding format for parameters is ASN.1, if an ASN.1 specification for this type of parameters exists.

  Parameters:
    `params` - the encoded parameters.
  Throws:
    `IOException` - on decoding errors, or if this parameter object has already been initialized.

### init

    public final void init(byte[] params,
                           String format)
                    throws IOException

  Imports the parameters from `params` and decodes them according to the specified decoding scheme. If `format` is null, the primary decoding format for parameters is used. The primary decoding format is ASN.1, if an ASN.1 specification for these parameters exists.

  Parameters:
    `params` - the encoded parameters.
    `format` - the name of the decoding scheme.
  Throws:
    `IOException` - on decoding errors, or if this parameter object has already been initialized.

### getParameterSpec

    public final AlgorithmParameterSpec getParameterSpec(Class paramSpec)
                                                  throws InvalidParameterSpecException

  Returns a (transparent) specification of this parameter object. `paramSpec` identifies the specification class in which the parameters should be returned. It could, for example, be `DSAParameterSpec.class`, to indicate that the parameters should be returned in an instance of the `DSAParameterSpec` class.

  Parameters:
    `paramSpec` - the specification class in which the parameters should be returned.
  Returns:
    the parameter specification.
  Throws:
    `InvalidParameterSpecException` - if the requested parameter specification is inappropriate for this parameter object, or if this parameter object has not been initialized.

### getEncoded

    public final byte[] getEncoded()
                            throws IOException

  Returns the parameters in their primary encoding format. The primary encoding format for parameters is ASN.1, if an ASN.1 specification for this type of parameters exists.

  Returns:
    the parameters encoded using their primary encoding format.
  Throws:
    `IOException` - on encoding errors, or if this parameter object has not been initialized.

### getEncoded

    public final byte[] getEncoded(String format)
                            throws IOException

  Returns the parameters encoded in the specified scheme. If `format` is null, the primary encoding format for parameters is used. The primary encoding format is ASN.1, if an ASN.1 specification for these parameters exists.

  Parameters:
    `format` - the name of the encoding format.
  Returns:
    the parameters encoded using the specified encoding scheme.
  Throws:
    `IOException` - on encoding errors, or if this parameter object has not been initialized.

### toString

    public final String toString()

  Returns a formatted string describing the parameters.

  Overrides:
    `toString` in class `Object`
  Returns:
    a formatted string describing the parameters, or null if this parameter object has not been initialized.

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