# Class Unknown

java.lang.Object
org.apache.bcel.classfile.Attribute
org.apache.bcel.classfile.Unknown

All Implemented Interfaces:
  `Cloneable, Node`

public final class Unknown extends Attribute
This class represents a reference to an unknown (i.e., application-specific) attribute of a class. It is instantiated from the `Attribute.readAttribute(java.io.DataInput, ConstantPool)` method. Applications that need to read in application-specific attributes should create an `UnknownAttributeReader` implementation and attach it via `Attribute.addAttributeReader(String, UnknownAttributeReader)`.

See Also:
  - `Attribute`
  - `UnknownAttributeReader`

- ## Field Summary

  ### Fields inherited from class Attribute

  `constant_pool, EMPTY_ARRAY, length, name_index, tag`

- ## Constructor Summary

  Constructors
  Constructor
  Description
  `Unknown(int nameIndex, int length, byte[] bytes, ConstantPool constantPool)`
  Constructs a new instance for a non-standard attribute.
  `Unknown(Unknown unknown)`
  Constructs a new instance from another instance.

- ## Method Summary

  Modifier and Type
  Method
  Description
  `void`
  `accept(Visitor v)`
  Called by objects that are traversing the nodes of the tree implicitly defined by the contents of a Java class.
  `Attribute`
  `copy(ConstantPool constantPool)`
  `void`
  `dump(DataOutputStream file)`
  Dumps unknown bytes to file stream.
  `byte[]`
  `getBytes()`
  `String`
  `getName()`
  `void`
  `setBytes(byte[] bytes)`
  `String`
  `toString()`

  ### Methods inherited from class Attribute

  `addAttributeReader, addAttributeReader, clone, getConstantPool, getLength, getNameIndex, getTag, println, readAttribute, readAttribute, removeAttributeReader, setConstantPool, setLength, setNameIndex`

  ### Methods inherited from class Object

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

- ## Constructor Details

  - ### Unknown

    public Unknown(int nameIndex, int length, byte[] bytes, ConstantPool constantPool)
    Constructs a new instance for a non-standard attribute.
    Parameters:
      `nameIndex` - Index in constant pool
      `length` - Content length in bytes
      `bytes` - Attribute contents
      `constantPool` - Array of constants

  - ### Unknown

    public Unknown(Unknown unknown)
    Constructs a new instance from another instance. Note that both objects use the same references (shallow copy). Use clone() for a physical copy.
    Parameters:
      `unknown` - Source.

- ## Method Details

  - ### accept

    public void accept(Visitor v)
    Called by objects that are traversing the nodes of the tree implicitly defined by the contents of a Java class. I.e., the hierarchy of methods, fields, attributes, etc. spawns a tree of objects.
    Specified by:
      `accept` in interface `Node`
    Specified by:
      `accept` in class `Attribute`
    Parameters:
      `v` - Visitor object

  - ### copy

    public Attribute copy(ConstantPool constantPool)
    Specified by:
      `copy` in class `Attribute`
    Parameters:
      `constantPool` - constant pool to save.
    Returns:
      deep copy of this attribute

  - ### dump

    public void dump(DataOutputStream file) throws IOException
    Dumps unknown bytes to file stream.
    Overrides:
      `dump` in class `Attribute`
    Parameters:
      `file` - Output file stream
    Throws:
      `IOException` - if an I/O error occurs.

  - ### getBytes

    public byte[] getBytes()
    Returns:
      data bytes.

  - ### getName

    public String getName()
    Overrides:
      `getName` in class `Attribute`
    Returns:
      name of attribute.

  - ### setBytes

    public void setBytes(byte[] bytes)
    Parameters:
      `bytes` - the bytes to set

  - ### toString

    public String toString()
    Overrides:
      `toString` in class `Attribute`
    Returns:
      String representation.