package?JExercise;

import?java.util.Stack;

public?class?Calculator??implements?MathSymbol{
		public?double?eval（String?expression）{
			String?str?=?infix2Suffix（expression）;			
			if（str?==?null）?{
	????????????throw?new?IllegalArgumentException（“expression?is?null!“）;
			}
			?String[]?strs?=?str.split（“\\s+“）;
			?Stack?stack?=?new?Stack（）;
			?for（int?i?=?0;?i?				?if（!Operator.isOperator（strs[i]））?{
		????????????????stack.push（strs[i]）;
				?}?else?{
					?Operator?op?=?Operator.getInstance（strs[i]）;
		????????????????double?right?=?Double.parseDouble（stack.pop（））;
		????????????????double?left?=?Double.parseDouble（stack.pop（））;
		????????????????double?result?=?op.eval（left?right）;
		????????????????stack.push（String.valueOf（result））;
				?
				?}
			?}?
			?return?Double.parseDouble（stack.pop（））;
		}
		public?String?infix2Suffix（String?expression）{
			if?（expression==null）{return?null;}
			char[]?chs=expression.toCharArray（）;
			
			Stack??stack=new?Stack（）;
			StringBuilder?sb?=new?StringBuilder（chs.length）;
			boolean?appendSeparator?=?false;
	????????boolean?sign?=?true;
	????????for（int?i=0;i	????????	char?c=?chs[i];
	????????	if?（c==BLANK）{
	????????		continue;
	????????	}
	????????	?if（appendSeparator）?{
	????????????????//?sb.append（SEPARATOR）;
	????????		?sb.append（SEPARATOR）;
	?????????????????appendSeparator?=?false;
	?????????????}
	????????	?if（isSign（c）?&&?sign）?{
	?????????????????sb.append（c）;
	?????????????????continue;
	?????????????}
	????????	?if（isNumber（c））?{
	?????????????????sign?=?false;
	?????????????????sb.append（c）;
	?????????????????continue;
	?????????????}??????????
	????????	?if（isLeftBracket（c））?{
	?????????????????stack.push（c）;
	?????????????????continue;????????????????
	?????????????}
	????????	??if（isRightBracket（c））?{
	??????????????????sign?=?false;
	??????????????????while（stack.peek（）?!=?LEFT_BRACKET）?{???????//查看棧頂對象而不移除它
	??????????????????????sb.append（SEPARATOR）;
	??????????????????????sb.append（stack.pop（））;
	??????????????????}
	??????????????????stack.pop（）;??????????????????????????????//移除棧頂對象并作為此函數的值返回該對象
	??????????????????continue;
	??????????????}
	????????	??appendSeparator?=?true;
	????????	??if（Operator.isOperator（c））?{
	????????		??sign?=?true;
	??????????????????if（stack.isEmpty（）?||?stack.peek（）?==?LEFT_BRACKET）?{
	??????????????????????stack.push（c）;??//把項壓入棧頂
	??????????????????????continue;
	??????????????????}
	??????????????????int?precedence?=?Operator.getPrority（c）;
	??????????????????while（!stack.isEmpty（）?&&?Operator.getPrority（stack.peek（））?>=?precedence）?{
	??????????????????????sb.append（SEPARATOR）;
	??????????????????????sb.append（stack.pop（））;
	??????????????????}
	??????????????????stack.push（c）;

	????????	??}
	????????}
	????????while?（!stack.isEmpty（））{
	????????	sb.append（SEPARATOR）;
	????????	sb.app

?屬性????????????大小?????日期????時間???名稱
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?????文件???????3544??2010-06-23?19:42??JExercise\Calculator.java

?????文件???????7597??2010-07-02?21:51??JExercise\CalculatorF.java

?????文件????????595??2010-07-02?21:48??JExercise\MathSymbol.java

?????文件???????4299??2010-07-02?21:48??JExercise\Operator.java

?????目錄??????????0??2010-07-12?15:59??JExercise

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????????????????16035????????????????????5