# 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).

Once an `AlgorithmParameters` object is obtained, 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`.

Every implementation of the Java platform is required to support the following standard `AlgorithmParameters` algorithms. For the "EC" algorithm, implementations must support the curves in parentheses. For the "RSASSA-PSS" algorithm, implementations must support the parameters in parentheses.

- `AES`
- `ChaCha20-Poly1305`
- `DESede`
- `DiffieHellman`
- `DSA`
- `EC` (secp256r1, secp384r1)
- `RSASSA-PSS` (MGF1 mask generation function and SHA-256 or SHA-384 hash algorithms)

These algorithms are described in the AlgorithmParameters section of the Java Security Standard Algorithm Names Specification. Consult the release documentation for your implementation to see if any other algorithms are supported.

Since:
  1.2
External Specifications
  - Java Security Standard Algorithm Names
See Also:
  - `AlgorithmParameterSpec`
  - `DSAParameterSpec`
  - `KeyPairGenerator`

## Constructor Summary

Constructors
Modifier
Constructor
Description
`protected`
`AlgorithmParameters(AlgorithmParametersSpi paramSpi, Provider provider, String algorithm)`
Creates an `AlgorithmParameters` object.

## Method Summary

Modifier and Type
Method
Description
`final String`
`getAlgorithm()`
Returns the name of the algorithm associated with this parameter object.
`final byte[]`
`getEncoded()`
Returns the parameters in their primary encoding format.
`final byte[]`
`getEncoded(String format)`
Returns the parameters encoded in the specified scheme.
`static AlgorithmParameters`
`getInstance(String algorithm)`
Returns a parameter object for the specified algorithm.
`static AlgorithmParameters`
`getInstance(String algorithm, String provider)`
Returns a parameter object for the specified algorithm.
`static AlgorithmParameters`
`getInstance(String algorithm, Provider provider)`
Returns a parameter object for the specified algorithm.
`final <T extends AlgorithmParameterSpec>
T`
`getParameterSpec(Class<T> paramSpec)`
Returns a (transparent) specification of this parameter object.
`final Provider`
`getProvider()`
Returns the provider of this parameter object.
`final void`
`init(byte[] params)`
Imports the specified parameters and decodes them according to the primary decoding format for parameters.
`final void`
`init(byte[] params, String format)`
Imports the parameters from `params` and decodes them according to the specified decoding scheme.
`final void`
`init(AlgorithmParameterSpec paramSpec)`
Initializes this parameter object using the parameters specified in `paramSpec`.
`final String`
`toString()`
Returns a formatted string describing the parameters.

### Methods declared in class Object

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

## Constructor Details

### AlgorithmParameters

protected AlgorithmParameters(AlgorithmParametersSpi paramSpi, Provider provider, String algorithm)
Creates an `AlgorithmParameters` object.

Parameters:
  `paramSpi` - the delegate
  `provider` - the provider
  `algorithm` - the algorithm

## Method Details

### 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
Returns a parameter object for the specified algorithm.

This method traverses the list of registered security providers, starting with the most preferred provider. A new `AlgorithmParameters` object encapsulating the `AlgorithmParametersSpi` implementation from the first provider that supports the specified algorithm is returned.

Note that the list of registered providers may be retrieved via the `Security.getProviders()` method.

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

Implementation Note:
  The JDK Reference Implementation additionally uses the `jdk.security.provider.preferred` `Security` property to determine the preferred provider order for the specified algorithm. This may be different from the order of providers returned by `Security.getProviders()`.
Parameters:
  `algorithm` - the name of the algorithm requested. See the AlgorithmParameters section in the Java Security Standard Algorithm Names Specification for information about standard algorithm names.
Returns:
  the new parameter object
Throws:
  `NoSuchAlgorithmException` - if no `Provider` supports an `AlgorithmParametersSpi` implementation for the specified algorithm
  `NullPointerException` - if `algorithm` is `null`
External Specifications
  - Java Security Standard Algorithm Names
See Also:
  - `Provider`

### getInstance

public static AlgorithmParameters getInstance(String algorithm, String provider) throws NoSuchAlgorithmException, NoSuchProviderException
Returns a parameter object for the specified algorithm.

A new `AlgorithmParameters` object encapsulating the `AlgorithmParametersSpi` implementation from the specified provider is returned. The specified provider must be registered in the security provider list.

Note that the list of registered providers may be retrieved via the `Security.getProviders()` method.

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. See the AlgorithmParameters section in the Java Security Standard Algorithm Names Specification for information about standard algorithm names.
  `provider` - the name of the provider.
Returns:
  the new parameter object
Throws:
  `IllegalArgumentException` - if the provider name is `null` or empty
  `NoSuchAlgorithmException` - if an `AlgorithmParametersSpi` implementation for the specified algorithm is not available from the specified provider
  `NoSuchProviderException` - if the specified provider is not registered in the security provider list
  `NullPointerException` - if `algorithm` is `null`
External Specifications
  - Java Security Standard Algorithm Names
See Also:
  - `Provider`

### getInstance

public static AlgorithmParameters getInstance(String algorithm, Provider provider) throws NoSuchAlgorithmException
Returns a parameter object for the specified algorithm.

A new `AlgorithmParameters` object encapsulating the `AlgorithmParametersSpi` implementation from the specified provider is returned. Note that the specified provider does not have to be registered in the provider list.

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. See the AlgorithmParameters section in the Java Security Standard Algorithm Names Specification for information about standard algorithm names.
  `provider` - the name of the provider.
Returns:
  the new parameter object
Throws:
  `IllegalArgumentException` - if the provider is `null`
  `NoSuchAlgorithmException` - if an `AlgorithmParameterGeneratorSpi` implementation for the specified algorithm is not available from the specified `Provider` object
  `NullPointerException` - if `algorithm` is `null`
Since:
  1.4
External Specifications
  - Java Security Standard Algorithm Names
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 <T extends AlgorithmParameterSpec> T getParameterSpec(Class<T> 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.

Type Parameters:
  `T` - the type of the parameter specification to be returned
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.