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Java example source code file (Method.java)

This example Java source code file (Method.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, classformatexception, code, constantpool, constantutf8, exceptiontable, fieldormethod, ioexception, linenumbertable, localvariabletable, method, string, stringbuffer, type

The Method.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 com.sun.org.apache.bcel.internal.generic.Type;
import java.io.*;

/**
 * This class represents the method info structure, i.e., the representation
 * for a method in the class. See JVM specification for details.
 * A method has access flags, a name, a signature and a number of attributes.
 *
 * @author  <A HREF="mailto:markus.dahm@berlin.de">M. Dahm
 */
public final class Method extends FieldOrMethod {
  /**
   * Empty constructor, all attributes have to be defined via `setXXX'
   * methods. Use at your own risk.
   */
  public Method() {}

  /**
   * Initialize from another object. Note that both objects use the same
   * references (shallow copy). Use clone() for a physical copy.
   */
  public Method(Method c) {
    super(c);
  }

  /**
   * Construct object from file stream.
   * @param file Input stream
   * @throws IOException
   * @throws ClassFormatException
   */
  Method(DataInputStream file, ConstantPool constant_pool)
    throws IOException, ClassFormatException
  {
    super(file, constant_pool);
  }

  /**
   * @param access_flags Access rights of method
   * @param name_index Points to field name in constant pool
   * @param signature_index Points to encoded signature
   * @param attributes Collection of attributes
   * @param constant_pool Array of constants
   */
  public Method(int access_flags, int name_index, int signature_index,
                Attribute[] attributes, ConstantPool constant_pool)
  {
    super(access_flags, name_index, signature_index, attributes, constant_pool);
  }

  /**
   * 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.visitMethod(this);
  }

  /**
   * @return Code attribute of method, if any
   */
  public final Code getCode() {
    for(int i=0; i < attributes_count; i++)
      if(attributes[i] instanceof Code)
        return (Code)attributes[i];

    return null;
  }

  /**
   * @return ExceptionTable attribute of method, if any, i.e., list all
   * exceptions the method may throw not exception handlers!
   */
  public final ExceptionTable getExceptionTable() {
    for(int i=0; i < attributes_count; i++)
      if(attributes[i] instanceof ExceptionTable)
        return (ExceptionTable)attributes[i];

    return null;
  }

  /** @return LocalVariableTable of code attribute if any, i.e. the call is forwarded
   * to the Code atribute.
   */
  public final LocalVariableTable getLocalVariableTable() {
    Code code = getCode();

    if(code != null)
      return code.getLocalVariableTable();
    else
      return null;
  }

  /** @return LineNumberTable of code attribute if any, i.e. the call is forwarded
   * to the Code atribute.
   */
  public final LineNumberTable getLineNumberTable() {
    Code code = getCode();

    if(code != null)
      return code.getLineNumberTable();
    else
      return null;
  }

  /**
   * Return string representation close to declaration format,
   * `public static void _main(String[] args) throws IOException', e.g.
   *
   * @return String representation of the method.
   */
  public final String toString() {
    ConstantUtf8  c;
    String        name, signature, access; // Short cuts to constant pool
    StringBuffer  buf;

    access = Utility.accessToString(access_flags);

    // Get name and signature from constant pool
    c = (ConstantUtf8)constant_pool.getConstant(signature_index,
                                                Constants.CONSTANT_Utf8);
    signature = c.getBytes();

    c = (ConstantUtf8)constant_pool.getConstant(name_index, Constants.CONSTANT_Utf8);
    name = c.getBytes();

    signature = Utility.methodSignatureToString(signature, name, access, true,
                                                getLocalVariableTable());
    buf = new StringBuffer(signature);

    for(int i=0; i < attributes_count; i++) {
      Attribute a = attributes[i];

      if(!((a instanceof Code) || (a instanceof ExceptionTable)))
        buf.append(" [" + a.toString() + "]");
    }

    ExceptionTable e = getExceptionTable();
    if(e != null) {
      String str = e.toString();
      if(!str.equals(""))
        buf.append("\n\t\tthrows " + str);
    }

    return buf.toString();
  }

  /**
   * @return deep copy of this method
   */
  public final Method copy(ConstantPool constant_pool) {
    return (Method)copy_(constant_pool);
  }

  /**
   * @return return type of method
   */
  public Type getReturnType() {
    return Type.getReturnType(getSignature());
  }

  /**
   * @return array of method argument types
   */
  public Type[] getArgumentTypes() {
    return Type.getArgumentTypes(getSignature());
  }
}

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