Module java.base
Package java.security

# Class Provider

java.lang.Object
java.util.Dictionary<K,V>
java.util.Hashtable<Object,Object>
java.util.Properties
java.security.Provider

All Implemented Interfaces:
  `Serializable`, `Cloneable`, `Map<Object,Object>`

Direct Known Subclasses:
  `AuthProvider`

public abstract class Provider extends Properties
This class represents a "provider" for the Java Security API, where a provider implements some or all parts of Java Security. Services that a provider may implement include:

- Algorithms (such as DSA, RSA, or SHA-256).
- Key generation, conversion, and management facilities (such as for algorithm-specific keys).

Some provider implementations may encounter unrecoverable internal errors during their operation, for example a failure to communicate with a security token. A `ProviderException` should be used to indicate such errors.

Please note that a provider can be used to implement any security service in Java that uses a pluggable architecture with a choice of implementations that fit underneath.

The service type `Provider` is reserved for use by the security framework. Services of this type cannot be added, removed, or modified by applications. The following attributes are automatically placed in each Provider object:

Attributes Automatically Placed in a Provider Object
Name | Value
--- | ---
`Provider.id name` | `String.valueOf(provider.getName())`
`Provider.id version` | `String.valueOf(provider.getVersionStr())`
`Provider.id info` | `String.valueOf(provider.getInfo())`
`Provider.id className` | `provider.getClass().getName()`

Each provider has a name and a version string. A provider normally identifies itself with a file named `java.security.Provider` in the resource directory `META-INF/services`. Security providers are looked up via the `ServiceLoader` mechanism using the `application class loader`.

Providers may be configured such that they are automatically installed and made available at runtime via the `Security.getProviders()` method. The mechanism for configuring and installing security providers is implementation-specific.

Implementation Note:
  The JDK implementation supports static registration of the security providers via the `conf/security/java.security` file in the Java installation directory. These providers are automatically installed by the JDK runtime, see The Provider Class in the Java Cryptography Architecture (JCA) Reference Guide for information about how a particular type of provider, the cryptographic service provider, works and is installed.
Since:
  1.1
See Also:
  - Serialized Form

- ## Nested Class Summary

  Nested Classes
  Modifier and Type
  Class
  Description
  `static class`
  `Provider.Service`
  The description of a security service.

- ## Field Summary

  ### Fields declared in class java.util.Properties

  `defaults`

- ## Constructor Summary

  Constructors
  Modifier
  Constructor
  Description
  `protected`
  `Provider(String name, double version, String info)`
  Deprecated.
  use `Provider(String, String, String)` instead.
  `protected`
  `Provider(String name, String versionStr, String info)`
  Constructs a provider with the specified name, version string, and information.

- ## Method Summary

  Modifier and Type
  Method
  Description
  `void`
  `clear()`
  Clears this provider so that it no longer contains the properties used to look up facilities implemented by the provider.
  `Object`
  `compute(Object key, BiFunction<? super Object,? super Object,? extends Object> remappingFunction)`
  Attempts to compute a mapping for the specified key and its current mapped value (or `null` if there is no current mapping).
  `Object`
  `computeIfAbsent(Object key, Function<? super Object,? extends Object> mappingFunction)`
  If the specified key is not already associated with a value (or is mapped to `null`), attempts to compute its value using the given mapping function and enters it into this map unless `null`.
  `Object`
  `computeIfPresent(Object key, BiFunction<? super Object,? super Object,? extends Object> remappingFunction)`
  If the value for the specified key is present and non-null, attempts to compute a new mapping given the key and its current mapped value.
  `Provider`
  `configure(String configArg)`
  Apply the supplied configuration argument to this provider instance and return the configured provider.
  `Set<Map.Entry<Object,Object>>`
  `entrySet()`
  Returns an unmodifiable Set view of the property entries contained in this Provider.
  `void`
  `forEach(BiConsumer<? super Object,? super Object> action)`
  Performs the given action for each entry in this map until all entries have been processed or the action throws an exception.
  `String`
  `getInfo()`
  Returns a human-readable description of the provider and its services.
  `String`
  `getName()`
  Returns the name of this provider.
  `Object`
  `getOrDefault(Object key, Object defaultValue)`
  Returns the value to which the specified key is mapped, or `defaultValue` if this map contains no mapping for the key.
  `Provider.Service`
  `getService(String type, String algorithm)`
  Get the service describing this Provider's implementation of the specified type of this algorithm or alias.
  `Set<Provider.Service>`
  `getServices()`
  Get an unmodifiable Set of all services supported by this Provider.
  `double`
  `getVersion()`
  Deprecated.
  use `getVersionStr()` instead.
  `String`
  `getVersionStr()`
  Returns the version string for this provider.
  `boolean`
  `isConfigured()`
  Check if this provider instance has been configured.
  `Set<Object>`
  `keySet()`
  Returns an unmodifiable Set view of the property keys contained in this provider.
  `void`
  `load(InputStream inStream)`
  Reads a property list (key and element pairs) from the input stream.
  `Object`
  `merge(Object key, Object value, BiFunction<? super Object,? super Object,? extends Object> remappingFunction)`
  If the specified key is not already associated with a value or is associated with null, associates it with the given value.
  `Object`
  `put(Object key, Object value)`
  Sets the `key` property to have the specified `value`.
  `void`
  `putAll(Map<?,?> t)`
  Copies all of the mappings from the specified Map to this provider.
  `Object`
  `putIfAbsent(Object key, Object value)`
  If the specified key is not already associated with a value (or is mapped to `null`) associates it with the given value and returns `null`, else returns the current value.
  `protected void`
  `putService(Provider.Service s)`
  Add a service.
  `Object`
  `remove(Object key)`
  Removes the `key` property (and its corresponding `value`).
  `boolean`
  `remove(Object key, Object value)`
  Removes the entry for the specified key only if it is currently mapped to the specified value.
  `protected void`
  `removeService(Provider.Service s)`
  Remove a service previously added using `putService()`.
  `Object`
  `replace(Object key, Object value)`
  Replaces the entry for the specified key only if it is currently mapped to some value.
  `boolean`
  `replace(Object key, Object oldValue, Object newValue)`
  Replaces the entry for the specified key only if currently mapped to the specified value.
  `void`
  `replaceAll(BiFunction<? super Object,? super Object,? extends Object> function)`
  Replaces each entry's value with the result of invoking the given function on that entry, in the order entries are returned by an entry set iterator, until all entries have been processed or the function throws an exception.
  `String`
  `toString()`
  Returns a string with the name and the version string of this provider.
  `Collection<Object>`
  `values()`
  Returns an unmodifiable Collection view of the property values contained in this provider.

  ### Methods declared in class java.util.Properties

  `getProperty, getProperty, list, list, load, loadFromXML, propertyNames, save, setProperty, store, store, storeToXML, storeToXML, storeToXML, stringPropertyNames`

  ### Methods declared in class java.util.Hashtable

  `clone, contains, containsKey, containsValue, elements, equals, get, hashCode, isEmpty, keys, rehash, size`

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

  `finalize, getClass, notify, notifyAll, wait, wait, wait`

- ## Constructor Details

  - ### Provider

    @Deprecated(since="9") protected Provider(String name, double version, String info)
    Deprecated.
    use `Provider(String, String, String)` instead.
    Constructs a provider with the specified name, version number, and information. Calling this constructor is equivalent to call the `Provider(String, String, String)` with `name` name, `Double.toString(version)`, and `info`.
    Parameters:
      `name` - the provider name.
      `version` - the provider version number.
      `info` - a description of the provider and its services.

  - ### Provider

    protected Provider(String name, String versionStr, String info)
    Constructs a provider with the specified name, version string, and information.

    The version string contains a version number optionally followed by other information separated by one of the characters of '+', '-'. The format for the version number is:

    >          ^[0-9]+(\.[0-9]+)*

    In order to return the version number in a double, when there are more than two components (separated by '.' as defined above), only the first two components are retained. The resulting string is then passed to `Double.valueOf(String)` to generate version number, i.e. `getVersion()`.

    If the conversion failed, value 0 will be used.

    Parameters:
      `name` - the provider name.
      `versionStr` - the provider version string.
      `info` - a description of the provider and its services.
    Since:
      9

- ## Method Details

  - ### configure

    public Provider configure(String configArg)
    Apply the supplied configuration argument to this provider instance and return the configured provider. Note that if this provider cannot be configured in-place, a new provider will be created and returned. Therefore, callers should always use the returned provider.
    Implementation Requirements:
      The default implementation throws `UnsupportedOperationException`. Subclasses should override this method only if a configuration argument is supported.
    Parameters:
      `configArg` - the configuration information for configuring this provider.
    Returns:
      a provider configured with the supplied configuration argument.
    Throws:
      `UnsupportedOperationException` - if a configuration argument is not supported.
      `NullPointerException` - if the supplied configuration argument is null.
      `InvalidParameterException` - if the supplied configuration argument is invalid.
    Since:
      9

  - ### isConfigured

    public boolean isConfigured()
    Check if this provider instance has been configured.
    Implementation Requirements:
      The default implementation returns true. Subclasses should override this method if the provider instance requires an explicit `configure` call after being constructed.
    Returns:
      true if no further configuration is needed, false otherwise.
    Since:
      9

  - ### getName

    public String getName()
    Returns the name of this provider.
    Returns:
      the name of this provider.

  - ### getVersion

    @Deprecated(since="9") public double getVersion()
    Deprecated.
    use `getVersionStr()` instead.
    Returns the version number for this provider.
    Returns:
      the version number for this provider.

  - ### getVersionStr

    public String getVersionStr()
    Returns the version string for this provider.
    Returns:
      the version string for this provider.
    Since:
      9

  - ### getInfo

    public String getInfo()
    Returns a human-readable description of the provider and its services. This may return an HTML page, with relevant links.
    Returns:
      a description of the provider and its services.

  - ### toString

    public String toString()
    Returns a string with the name and the version string of this provider.
    Overrides:
      `toString` in class `Hashtable<Object,Object>`
    Returns:
      the string with the name and the version string for this provider.

  - ### clear

    public void clear()
    Clears this provider so that it no longer contains the properties used to look up facilities implemented by the provider.

    If a security manager is enabled, its `checkSecurityAccess` method is called with the string `"clearProviderProperties."+name` (where `name` is the provider name) to see if it's ok to clear this provider.

    Specified by:
      `clear` in interface `Map<Object,Object>`
    Overrides:
      `clear` in class `Hashtable<Object,Object>`
    Throws:
      `SecurityException` - if a security manager exists and its `SecurityManager.checkSecurityAccess(java.lang.String)` method denies access to clear this provider
    Since:
      1.2

  - ### load

    public void load(InputStream inStream) throws IOException
    Reads a property list (key and element pairs) from the input stream.
    Overrides:
      `load` in class `Properties`
    Parameters:
      `inStream` - the input stream.
    Throws:
      `IOException` - if an error occurred when reading from the input stream.
    See Also:
      - `Properties.load(java.io.Reader)`

  - ### putAll

    public void putAll(Map<?,?> t)
    Copies all of the mappings from the specified Map to this provider. These mappings will replace any properties that this provider had for any of the keys currently in the specified Map.
    Specified by:
      `putAll` in interface `Map<Object,Object>`
    Overrides:
      `putAll` in class `Hashtable<Object,Object>`
    Parameters:
      `t` - mappings to be stored in this map
    Since:
      1.2

  - ### entrySet

    public Set<Map.Entry<Object,Object>> entrySet()
    Returns an unmodifiable Set view of the property entries contained in this Provider.
    Specified by:
      `entrySet` in interface `Map<Object,Object>`
    Overrides:
      `entrySet` in class `Hashtable<Object,Object>`
    Returns:
      a set view of the mappings contained in this map
    Since:
      1.2
    See Also:
      - `Map.Entry`

  - ### keySet

    public Set<Object> keySet()
    Returns an unmodifiable Set view of the property keys contained in this provider.
    Specified by:
      `keySet` in interface `Map<Object,Object>`
    Overrides:
      `keySet` in class `Hashtable<Object,Object>`
    Returns:
      a set view of the keys contained in this map
    Since:
      1.2

  - ### values

    public Collection<Object> values()
    Returns an unmodifiable Collection view of the property values contained in this provider.
    Specified by:
      `values` in interface `Map<Object,Object>`
    Overrides:
      `values` in class `Hashtable<Object,Object>`
    Returns:
      a collection view of the values contained in this map
    Since:
      1.2

  - ### put

    public Object put(Object key, Object value)
    Sets the `key` property to have the specified `value`.

    If a security manager is enabled, its `checkSecurityAccess` method is called with the string `"putProviderProperty."+name`, where `name` is the provider name, to see if it's ok to set this provider's property values.

    Specified by:
      `put` in interface `Map<Object,Object>`
    Overrides:
      `put` in class `Hashtable<Object,Object>`
    Parameters:
      `key` - the hashtable key
      `value` - the value
    Returns:
      the previous value of the specified key in this hashtable, or `null` if it did not have one
    Throws:
      `SecurityException` - if a security manager exists and its `SecurityManager.checkSecurityAccess(java.lang.String)` method denies access to set property values.
    Since:
      1.2
    See Also:
      - `Object.equals(Object)`
      - `Hashtable.get(Object)`

  - ### putIfAbsent

    public Object putIfAbsent(Object key, Object value)
    If the specified key is not already associated with a value (or is mapped to `null`) associates it with the given value and returns `null`, else returns the current value.

    If a security manager is enabled, its `checkSecurityAccess` method is called with the string `"putProviderProperty."+name`, where `name` is the provider name, to see if it's ok to set this provider's property values.

    Parameters:
      `key` - key with which the specified value is to be associated
      `value` - value to be associated with the specified key
    Returns:
      the previous value associated with the specified key, or `null` if there was no mapping for the key. (A `null` return can also indicate that the map previously associated `null` with the key, if the implementation supports null values.)
    Throws:
      `SecurityException` - if a security manager exists and its `SecurityManager.checkSecurityAccess(java.lang.String)` method denies access to set property values.
    Since:
      1.8

  - ### remove

    public Object remove(Object key)
    Removes the `key` property (and its corresponding `value`).

    If a security manager is enabled, its `checkSecurityAccess` method is called with the string `"removeProviderProperty."+name`, where `name` is the provider name, to see if it's ok to remove this provider's properties.

    Specified by:
      `remove` in interface `Map<Object,Object>`
    Overrides:
      `remove` in class `Hashtable<Object,Object>`
    Parameters:
      `key` - the key that needs to be removed
    Returns:
      the value to which the key had been mapped in this hashtable, or `null` if the key did not have a mapping
    Throws:
      `SecurityException` - if a security manager exists and its `SecurityManager.checkSecurityAccess(java.lang.String)` method denies access to remove this provider's properties.
    Since:
      1.2

  - ### remove

    public boolean remove(Object key, Object value)
    Removes the entry for the specified key only if it is currently mapped to the specified value.

    If a security manager is enabled, its `checkSecurityAccess` method is called with the string `"removeProviderProperty."+name`, where `name` is the provider name, to see if it's ok to remove this provider's properties.

    Parameters:
      `key` - key with which the specified value is associated
      `value` - value expected to be associated with the specified key
    Returns:
      `true` if the value was removed
    Throws:
      `SecurityException` - if a security manager exists and its `SecurityManager.checkSecurityAccess(java.lang.String)` method denies access to remove this provider's properties.
    Since:
      1.8

  - ### replace

    public boolean replace(Object key, Object oldValue, Object newValue)
    Replaces the entry for the specified key only if currently mapped to the specified value.

    If a security manager is enabled, its `checkSecurityAccess` method is called with the string `"putProviderProperty."+name`, where `name` is the provider name, to see if it's ok to set this provider's property values.

    Parameters:
      `key` - key with which the specified value is associated
      `oldValue` - value expected to be associated with the specified key
      `newValue` - value to be associated with the specified key
    Returns:
      `true` if the value was replaced
    Throws:
      `SecurityException` - if a security manager exists and its `SecurityManager.checkSecurityAccess(java.lang.String)` method denies access to set property values.
    Since:
      1.8

  - ### replace

    public Object replace(Object key, Object value)
    Replaces the entry for the specified key only if it is currently mapped to some value.

    If a security manager is enabled, its `checkSecurityAccess` method is called with the string `"putProviderProperty."+name`, where `name` is the provider name, to see if it's ok to set this provider's property values.

    Parameters:
      `key` - key with which the specified value is associated
      `value` - value to be associated with the specified key
    Returns:
      the previous value associated with the specified key, or `null` if there was no mapping for the key. (A `null` return can also indicate that the map previously associated `null` with the key, if the implementation supports null values.)
    Throws:
      `SecurityException` - if a security manager exists and its `SecurityManager.checkSecurityAccess(java.lang.String)` method denies access to set property values.
    Since:
      1.8

  - ### replaceAll

    public void replaceAll(BiFunction<? super Object,? super Object,? extends Object> function)
    Replaces each entry's value with the result of invoking the given function on that entry, in the order entries are returned by an entry set iterator, until all entries have been processed or the function throws an exception.

    If a security manager is enabled, its `checkSecurityAccess` method is called with the string `"putProviderProperty."+name`, where `name` is the provider name, to see if it's ok to set this provider's property values.

    Parameters:
      `function` - the function to apply to each entry
    Throws:
      `SecurityException` - if a security manager exists and its `SecurityManager.checkSecurityAccess(java.lang.String)` method denies access to set property values.
    Since:
      1.8

  - ### compute

    public Object compute(Object key, BiFunction<? super Object,? super Object,? extends Object> remappingFunction)
    Attempts to compute a mapping for the specified key and its current mapped value (or `null` if there is no current mapping).

    If a security manager is enabled, its `checkSecurityAccess` method is called with the strings `"putProviderProperty."+name` and `"removeProviderProperty."+name`, where `name` is the provider name, to see if it's ok to set this provider's property values and remove this provider's properties.

    Specified by:
      `compute` in interface `Map<Object,Object>`
    Overrides:
      `compute` in class `Hashtable<Object,Object>`
    Parameters:
      `key` - key with which the specified value is to be associated
      `remappingFunction` - the remapping function to compute a value
    Returns:
      the new value associated with the specified key, or null if none
    Throws:
      `SecurityException` - if a security manager exists and its `SecurityManager.checkSecurityAccess(java.lang.String)` method denies access to set property values or remove properties.
    Since:
      1.8

  - ### computeIfAbsent

    public Object computeIfAbsent(Object key, Function<? super Object,? extends Object> mappingFunction)
    If the specified key is not already associated with a value (or is mapped to `null`), attempts to compute its value using the given mapping function and enters it into this map unless `null`.

    If a security manager is enabled, its `checkSecurityAccess` method is called with the strings `"putProviderProperty."+name` and `"removeProviderProperty."+name`, where `name` is the provider name, to see if it's ok to set this provider's property values and remove this provider's properties.

    Specified by:
      `computeIfAbsent` in interface `Map<Object,Object>`
    Overrides:
      `computeIfAbsent` in class `Hashtable<Object,Object>`
    Parameters:
      `key` - key with which the specified value is to be associated
      `mappingFunction` - the mapping function to compute a value
    Returns:
      the current (existing or computed) value associated with the specified key, or null if the computed value is null
    Throws:
      `SecurityException` - if a security manager exists and its `SecurityManager.checkSecurityAccess(java.lang.String)` method denies access to set property values and remove properties.
    Since:
      1.8

  - ### computeIfPresent

    public Object computeIfPresent(Object key, BiFunction<? super Object,? super Object,? extends Object> remappingFunction)
    If the value for the specified key is present and non-null, attempts to compute a new mapping given the key and its current mapped value.

    If a security manager is enabled, its `checkSecurityAccess` method is called with the strings `"putProviderProperty."+name` and `"removeProviderProperty."+name`, where `name` is the provider name, to see if it's ok to set this provider's property values and remove this provider's properties.

    Specified by:
      `computeIfPresent` in interface `Map<Object,Object>`
    Overrides:
      `computeIfPresent` in class `Hashtable<Object,Object>`
    Parameters:
      `key` - key with which the specified value is to be associated
      `remappingFunction` - the remapping function to compute a value
    Returns:
      the new value associated with the specified key, or null if none
    Throws:
      `SecurityException` - if a security manager exists and its `SecurityManager.checkSecurityAccess(java.lang.String)` method denies access to set property values or remove properties.
    Since:
      1.8

  - ### merge

    public Object merge(Object key, Object value, BiFunction<? super Object,? super Object,? extends Object> remappingFunction)
    If the specified key is not already associated with a value or is associated with null, associates it with the given value. Otherwise, replaces the value with the results of the given remapping function, or removes if the result is null. This method may be of use when combining multiple mapped values for a key.

    If a security manager is enabled, its `checkSecurityAccess` method is called with the strings `"putProviderProperty."+name` and `"removeProviderProperty."+name`, where `name` is the provider name, to see if it's ok to set this provider's property values and remove this provider's properties.

    Specified by:
      `merge` in interface `Map<Object,Object>`
    Overrides:
      `merge` in class `Hashtable<Object,Object>`
    Parameters:
      `key` - key with which the resulting value is to be associated
      `value` - the non-null value to be merged with the existing value associated with the key or, if no existing value or a null value is associated with the key, to be associated with the key
      `remappingFunction` - the remapping function to recompute a value if present
    Returns:
      the new value associated with the specified key, or null if no value is associated with the key
    Throws:
      `SecurityException` - if a security manager exists and its `SecurityManager.checkSecurityAccess(java.lang.String)` method denies access to set property values or remove properties.
    Since:
      1.8

  - ### getOrDefault

    public Object getOrDefault(Object key, Object defaultValue)
    Description copied from interface: `Map`
    Returns the value to which the specified key is mapped, or `defaultValue` if this map contains no mapping for the key.
    Parameters:
      `key` - the key whose associated value is to be returned
      `defaultValue` - the default mapping of the key
    Returns:
      the value to which the specified key is mapped, or `defaultValue` if this map contains no mapping for the key
    Since:
      1.8

  - ### forEach

    public void forEach(BiConsumer<? super Object,? super Object> action)
    Description copied from interface: `Map`
    Performs the given action for each entry in this map until all entries have been processed or the action throws an exception. Unless otherwise specified by the implementing class, actions are performed in the order of entry set iteration (if an iteration order is specified.) Exceptions thrown by the action are relayed to the caller.
    Parameters:
      `action` - The action to be performed for each entry
    Since:
      1.8

  - ### getService

    public Provider.Service getService(String type, String algorithm)
    Get the service describing this Provider's implementation of the specified type of this algorithm or alias. If no such implementation exists, this method returns null. If there are two matching services, one added to this provider using `putService()` and one added via `put()`, the service added via `putService()` is returned.
    Parameters:
      `type` - the type of `service` requested (for example, `MessageDigest`)
      `algorithm` - the case insensitive algorithm name (or alternate alias) of the service requested (for example, `SHA-1`)
    Returns:
      the service describing this Provider's matching service or null if no such service exists
    Throws:
      `NullPointerException` - if type or algorithm is null
    Since:
      1.5

  - ### getServices

    public Set<Provider.Service> getServices()
    Get an unmodifiable Set of all services supported by this Provider.
    Returns:
      an unmodifiable Set of all services supported by this Provider
    Since:
      1.5

  - ### putService

    protected void putService(Provider.Service s)
    Add a service. If a service of the same type with the same algorithm name exists and it was added using `putService()`, it is replaced by the new service. This method also places information about this service in the provider's Hashtable values in the format described in the Java Cryptography Architecture (JCA) Reference Guide.

    Also, if there is a security manager, its `checkSecurityAccess` method is called with the string `"putProviderProperty."+name`, where `name` is the provider name, to see if it's ok to set this provider's property values. If the default implementation of `checkSecurityAccess` is used (that is, that method is not overridden), then this results in a call to the security manager's `checkPermission` method with a `SecurityPermission("putProviderProperty."+name)` permission.

    Parameters:
      `s` - the Service to add
    Throws:
      `SecurityException` - if a security manager exists and its `SecurityManager.checkSecurityAccess(java.lang.String)` method denies access to set property values.
      `NullPointerException` - if s is null
    Since:
      1.5

  - ### removeService

    protected void removeService(Provider.Service s)
    Remove a service previously added using `putService()`. The specified service is removed from this provider. It will no longer be returned by `getService()` and its information will be removed from this provider's Hashtable.

    Also, if there is a security manager, its `checkSecurityAccess` method is called with the string `"removeProviderProperty."+name`, where `name` is the provider name, to see if it's ok to remove this provider's properties. If the default implementation of `checkSecurityAccess` is used (that is, that method is not overridden), then this results in a call to the security manager's `checkPermission` method with a `SecurityPermission("removeProviderProperty."+name)` permission.

    Parameters:
      `s` - the Service to be removed
    Throws:
      `SecurityException` - if a security manager exists and its `SecurityManager.checkSecurityAccess(java.lang.String)` method denies access to remove this provider's properties.
      `NullPointerException` - if s is null
    Since:
      1.5