operator.java

一个非常有用的操作MCRSOFT EXCEL文件的工具。可以用JAVA方便的新建

/*********************************************************************
*
*      Copyright (C) 2002 Andrew Khan
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
***************************************************************************/

package jxl.biff.formula;

import java.util.Stack;
import java.util.ArrayList;

/**
 * An operator is a node in a parse tree.  Its children can be other
 * operators or operands
 * Arithmetic operators and functions are all considered operators
 */
abstract class Operator extends ParseItem
{
  /**
   * The items which this operator manipulates. There will be at most two
   */
  private ParseItem[] operands;

  /**
   * Constructor
   */
  public Operator()
  {
    operands = new ParseItem[0];
  }
  
  /**
   * Tells the operands to use the alternate code
   */
  protected void setOperandAlternateCode()
  {
    for (int i = 0 ; i < operands.length ; i++)
    {
      operands[i].setAlternateCode();
    }
  }

  /**
   * Adds operands to this item
   */
  protected void add(ParseItem n)
  {
    n.setParent(this);

    // Grow the array
    ParseItem[] newOperands = new ParseItem[operands.length + 1];
    System.arraycopy(operands, 0, newOperands, 0, operands.length);
    newOperands[operands.length] = n;
    operands = newOperands;
  }

  /** 
   * Gets the operands for this operator from the stack 
   */
  public abstract void getOperands(Stack s);

  /**
   * Gets the operands ie. the children of the node
   */
  protected ParseItem[] getOperands()
  {
    return operands;
  }

  /**
   * Gets the precedence for this operator.  Operator precedents run from 
   * 1 to 5, one being the highest, 5 being the lowest
   *
   * @return the operator precedence
   */
  abstract int getPrecedence();

}