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Java example source code file (Unknown.java)

This example Java source code file (Unknown.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

attribute, constantpool, datainputstream, hashmap, ioexception, iterator, string, unknown, util

The Unknown.java Java example source code

/*
 * reserved comment block
 * DO NOT REMOVE OR ALTER!
 */
package com.sun.org.apache.bcel.internal.classfile;

/* ====================================================================
 * The Apache Software License, Version 1.1
 *
 * Copyright (c) 2001 The Apache Software Foundation.  All rights
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution,
 *    if any, must include the following acknowledgment:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowledgment may appear in the software itself,
 *    if and wherever such third-party acknowledgments normally appear.
 *
 * 4. The names "Apache" and "Apache Software Foundation" and
 *    "Apache BCEL" must not be used to endorse or promote products
 *    derived from this software without prior written permission. For
 *    written permission, please contact apache@apache.org.
 *
 * 5. Products derived from this software may not be called "Apache",
 *    "Apache BCEL", nor may "Apache" appear in their name, without
 *    prior written permission of the Apache Software Foundation.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 */

import com.sun.org.apache.bcel.internal.Constants;
import java.io.*;
import java.util.*;

/**
 * This class represents a reference to an unknown (i.e.,
 * application-specific) attribute of a class.  It is instantiated from the
 * <em>Attribute.readAttribute() method.  Applications that need to
 * read in application-specific attributes should create an <a
 * href="./AttributeReader.html">AttributeReader</a> implementation and
 * attach it via <a
 * href="./Attribute.html#addAttributeReader(java.lang.String,
 * com.sun.org.apache.bcel.internal.classfile.AttributeReader)">Attribute.addAttributeReader</a>.

 *
 * @see com.sun.org.apache.bcel.internal.classfile.Attribute
 * @see com.sun.org.apache.bcel.internal.classfile.AttributeReader
 * @author  <A HREF="mailto:markus.dahm@berlin.de">M. Dahm
 */
public final class Unknown extends Attribute {
  private byte[] bytes;
  private String name;

  private static HashMap unknown_attributes = new HashMap();

  /** @return array of unknown attributes, but just one for each kind.
   */
  static Unknown[] getUnknownAttributes() {
    Unknown[] unknowns = new Unknown[unknown_attributes.size()];
    Iterator  entries  = unknown_attributes.values().iterator();

    for(int i=0; entries.hasNext(); i++)
      unknowns[i] = (Unknown)entries.next();

    unknown_attributes.clear();
    return unknowns;
  }

  /**
   * Initialize from another object. Note that both objects use the same
   * references (shallow copy). Use clone() for a physical copy.
   */
  public Unknown(Unknown c) {
    this(c.getNameIndex(), c.getLength(), c.getBytes(), c.getConstantPool());
  }

  /**
   * Create a non-standard attribute.
   *
   * @param name_index Index in constant pool
   * @param length Content length in bytes
   * @param bytes Attribute contents
   * @param constant_pool Array of constants
   */
  public Unknown(int name_index, int length, byte[] bytes,
                 ConstantPool constant_pool)
  {
    super(Constants.ATTR_UNKNOWN, name_index, length, constant_pool);
    this.bytes = bytes;

    name = ((ConstantUtf8)constant_pool.getConstant(name_index,
                                                    Constants.CONSTANT_Utf8)).getBytes();
    unknown_attributes.put(name, this);
  }

  /**
   * Construct object from file stream.
   * @param name_index Index in constant pool
   * @param length Content length in bytes
   * @param file Input stream
   * @param constant_pool Array of constants
   * @throws IOException
   */
  Unknown(int name_index, int length, DataInputStream file,
          ConstantPool constant_pool)
       throws IOException
  {
    this(name_index, length, (byte [])null, constant_pool);

    if(length > 0) {
      bytes = new byte[length];
      file.readFully(bytes);
    }
  }

  /**
   * Called by objects that are traversing the nodes of the tree implicitely
   * defined by the contents of a Java class. I.e., the hierarchy of methods,
   * fields, attributes, etc. spawns a tree of objects.
   *
   * @param v Visitor object
   */
  public void accept(Visitor v) {
    v.visitUnknown(this);
  }
  /**
   * Dump unknown bytes to file stream.
   *
   * @param file Output file stream
   * @throws IOException
   */
  public final void dump(DataOutputStream file) throws IOException
  {
    super.dump(file);
    if(length > 0)
      file.write(bytes, 0, length);
  }
  /**
   * @return data bytes.
   */
  public final byte[] getBytes() { return bytes; }

  /**
   * @return name of attribute.
   */
  public final String getName() { return name; }

  /**
   * @param bytes.
   */
  public final void setBytes(byte[] bytes) {
    this.bytes = bytes;
  }

  /**
   * @return String representation.
   */
  public final String toString() {
    if(length == 0 || bytes == null)
      return "(Unknown attribute " + name + ")";

    String hex;
    if(length > 10) {
      byte[] tmp = new byte[10];
      System.arraycopy(bytes, 0, tmp, 0, 10);
      hex = Utility.toHexString(tmp) + "... (truncated)";
    }
    else
      hex = Utility.toHexString(bytes);

    return "(Unknown attribute " + name + ": " + hex + ")";
  }

  /**
   * @return deep copy of this attribute
   */
  public Attribute copy(ConstantPool constant_pool) {
    Unknown c = (Unknown)clone();

    if(bytes != null)
      c.bytes = (byte[])bytes.clone();

    c.constant_pool = constant_pool;
    return c;
  }
}

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