abstractexpressionevaluation.java

<算法导论>第二版大部分算法实现. 1. 各类排序和顺序统计学相关 2. 数据结构 2.1 基本数据结构 2.2 散列表 2.3 二叉查找树 2.4 红黑树 2.5 数据结构

/*
 * Copyright (C) 2003-2008 Wang Pengcheng <[e-mail]>
 * Permission is granted to copy, distribute and/or modify this
 * document under the terms of the GNU Free Documentation License,
 * Version 2.0 or any later version published by the Free Software Foundation;
 * with no Invariant Sections.
 * You may obtain a copy of the License at
 *   http://www.gnu.org/licenses/lgpl.txt
 */
//20 Feb 2008
package cn.edu.whu.iss.algorithm.unit10.expression.evaluation;

/**
 * Abstract expression evaluation.
 * @author wpc
 * @version 0.0.1
 */
public abstract class AbstractExpressionEvaluation implements
		EvaluateExpression {

	/**
	 * saving expression
	 */
	protected String expression;
	/**
	 * the operator +
	 */
	public static final char OPERATOR_ADD = '+';
	public static final char OPERATOR_MINUS = '-';
	public static final char OPERATOR_MULTI = '*';
	public static final char OPERATOR_DIV = '/';
	public static final char OPERATOR_POW = '^';
	public static final char OPERATOR_LEFT_BRACKET = '(';
	public static final char OPERATOR_RIGHT_BRACKET = ')';
	public static final String EMPTY_STR = "";
	public static final int DEFAULT_SCALE = 10;
	/**
	 * the negative sign -number
	 */
	public static final String NEGATIVE_SIGN = "-negative";
	public static final char NUMBER_POINT = '.';
	
	public static final char[] CHAR_OPERA ={
		OPERATOR_ADD,OPERATOR_MINUS,OPERATOR_MULTI,OPERATOR_DIV,OPERATOR_LEFT_BRACKET,
		OPERATOR_RIGHT_BRACKET
	};
	
	public static final int WITHOUD_BRACKET_END = 4;
	
	/**
	 * Check the char is operator or not
	 * @param c the char
	 * @return true is the operator
	 */
	public static boolean isCharOpera(char c){
		for(int i=0;i<CHAR_OPERA.length;i++){
			if(c==CHAR_OPERA[i]){
				return true;
			}
		}
		return false;
	}
	
	/**
	 * Check the char is the operator divide or multiplication 
	 * @param s the String will be used the string.charAt(0)
	 * @return true is the divide or multiplication,otherwise is null or not 
	 */
	public static boolean isOperaDivOrMULTI(String s){
		if(s==null){
			return false;
		}
		return isOperaDivOrMULTI(s.charAt(0));
	}
	
	/**
	 * Check the char is the operator divide or multiplication 
	 * @param s the char
	 * @return true is the divide or multiplication,otherwise is null or not 
	 */
	public static boolean isOperaDivOrMULTI(char s){
		if(s==OPERATOR_DIV||s==OPERATOR_MULTI){
			return true;
		}else{
			return false;
		}
	}
	
	/**
	 * Check the string is the negative sign
	 * @param s the expression or number
	 * @return true is the negative sign
	 */
	public static boolean isNegativeSign(String s){
		if(s!=null&&s.equals(NEGATIVE_SIGN)){
			return true;
		}else{
			return false;
		}
		
	}
	
	/**
	 * Check the expression is the border( null or "(" )
	 * @param s the expression
	 * @return true is the border 
	 */
	public static boolean isBorder(String s){
		if(s==null||s.charAt(0)==OPERATOR_LEFT_BRACKET){
			return true;
		}else{
			return false;
		}
	}
	
	public static boolean isNumberPoint(char c){
		return c==NUMBER_POINT;
	}
}