expressionanalyze.java

一个关于公式分析得java小程序

							break;
						}
						
					}
				if(!findThird)
					throw new Exception ("there are not so much variables,the value '"
											+ value3 + "' is not needed");
		}
		//以下是表达式求值的算符优先算法。公式以"#"做结束符。
		//设optr和opnd分别为运算符栈和操作数栈
		Stack optr = new Stack(); //存储操作符的栈
		Stack opnd = new Stack();	//存储操作数的栈
		optr.push("#");
		current = elemList;
		while(!(current.data.equals("#") && optr.top().equals("#"))){
			//如果不是运算符，则直接入操作数栈
			if(!current.isOperator){
				opnd.push(current.data);
				current = current.next;
			}
			else{
				int indexOfFirst = 0,indexOfLast = 0;
				boolean flagOfFirst = false,flagOfLast = false;
				for(int i = 0;i < keywords.length;i++){
					if(optr.top().equals(keywords[i])){
						indexOfLast = i;
						flagOfLast = true;
					}
					if(current.data.equals(keywords[i])){
						indexOfFirst = i;
						flagOfFirst = true;
					}
					if(flagOfLast && flagOfFirst)
						break;
				}
				if(!flagOfLast)
					throw new Exception ("the operator '" + optr.top() 
											+ "' is not supported");
				if(!flagOfFirst)
					throw new Exception ("the operator '" + current.data 
											+ "' is not supported");
				flagOfLast = false;
				flagOfFirst = false;
				switch(PRI[indexOfLast][indexOfFirst]){
					case '<' ://栈顶元素优先级低
						optr.push(current.data);
						current = current.next;
						break;
					case '=' ://脱括弧、计算单目运算并接受下一个字符串
						optr.pop();
						current = current.next;
						boolean isOptr = false;
						for(int i = 0;i < keywords.length;i++)
							if(optr.top().equals(keywords[i])){
								if(keywords[i].length() > 1)	
									isOptr = true;
								break;
							}
						if(!isOptr)
							break;
						isOptr = false;
						//强制类型转换，若转换不成功则说明是变量
						try {
							firstDouTemp = Double.parseDouble(opnd.top());
						}
						catch (NumberFormatException e){
							if(opnd.top().equals(firstStr))
								firstDouTemp = firstDou;
							else if(opnd.top().equals(secondStr))
								firstDouTemp = secondDou;
							else if(opnd.top().equals(thirdStr))
								firstDouTemp = thirdDou;
							else
								throw new Exception ("the value of '" + opnd.top() 
														+ "' is not found");
						}
						opnd.pop();
						if(optr.top().equals("abs"))
							opnd.push(new Double(Math.abs(firstDouTemp)).toString());
						else if(optr.top().equals("acos")){
							if(Math.abs(firstDouTemp) > 1)
								throw new Exception("the absolute value of the argument '" 
								+ firstDouTemp + "' that 'acos' takes is greater than 1");
							opnd.push(new Double(Math.acos(firstDouTemp)).toString());
						}
						else if(optr.top().equals("asin")){
							if(Math.abs(firstDouTemp) > 1)
								throw new Exception("the absolute value of the argument '" 
								+ firstDouTemp + "' that 'asin' takes is greater than 1");
							opnd.push(new Double(Math.asin(firstDouTemp)).toString());
						}
						else if(optr.top().equals("atan"))
							opnd.push(new Double(Math.atan(firstDouTemp)).toString());
						else if(optr.top().equals("cbrt"))
							opnd.push(new Double(Math.cbrt(firstDouTemp)).toString());
						else if(optr.top().equals("cos"))
							opnd.push(new Double(Math.cos(firstDouTemp)).toString());
						else if(optr.top().equals("cosh"))
							opnd.push(new Double(Math.cosh(firstDouTemp)).toString());
						else if(optr.top().equals("ceil"))
							opnd.push(new Double(Math.ceil(firstDouTemp)).toString());
						else if(optr.top().equals("exp"))
							opnd.push(new Double(Math.exp(firstDouTemp)).toString());
						else if(optr.top().equals("expm1"))
							opnd.push(new Double(Math.expm1(firstDouTemp)).toString());
						else if(optr.top().equals("floor"))
							opnd.push(new Double(Math.floor(firstDouTemp)).toString());
						else if(optr.top().equals("log")){
							if(firstDouTemp < 0)
								throw new Exception("the argument '" + firstDouTemp 
									+ "' that 'log' takes is less than zero");
							opnd.push(new Double(Math.log(firstDouTemp)).toString());
						}
						else if(optr.top().equals("log10")){
							if(firstDouTemp < 0)
								throw new Exception("the argument '" + firstDouTemp 
									+ "' that 'log10' takes is less than zero");
							opnd.push(new Double(Math.log10(firstDouTemp)).toString());
						}
						else if(optr.top().equals("log1p")){
							if(firstDouTemp < -1)
								throw new Exception("the argument '" + firstDouTemp 
									+ "' that 'log1p' takes is less than -1");
							opnd.push(new Double(Math.log1p(firstDouTemp)).toString());
						}
						else if(optr.top().equals("rint"))
							opnd.push(new Double(Math.rint(firstDouTemp)).toString());
						else if(optr.top().equals("round"))
							opnd.push(new Double(Math.round(firstDouTemp)).toString());
						else if(optr.top().equals("signum"))
							opnd.push(new Double(Math.signum(firstDouTemp)).toString());
						else if(optr.top().equals("sin"))
							opnd.push(new Double(Math.sin(firstDouTemp)).toString());
						else if(optr.top().equals("sinh"))
							opnd.push(new Double(Math.sinh(firstDouTemp)).toString());
						else if(optr.top().equals("sqrt")){
							if(firstDouTemp < 0)
								throw new Exception("the argument '" + firstDouTemp 
									+ "' that 'sqrt' takes is less than zero");
							opnd.push(new Double(Math.sqrt(firstDouTemp)).toString());
						}
						else if(optr.top().equals("tan"))
							opnd.push(new Double(Math.tan(firstDouTemp)).toString());
						else if(optr.top().equals("tanh"))
							opnd.push(new Double(Math.tanh(firstDouTemp)).toString());
						else if(optr.top().equals("toDegrees"))
							opnd.push(new Double(Math.toDegrees(firstDouTemp)).toString());
						else if(optr.top().equals("toRadians"))
							opnd.push(new Double(Math.toRadians(firstDouTemp)).toString());
						else 
							throw new Exception ("the operator '" + optr.top() 
													+ "' is not supported");	
						optr.pop();
						break;
					case '@' ://表达式输入有误
						throw new Exception ("the operators '" + keywords[indexOfLast] 
												+ "' and '" + keywords[indexOfFirst] 
												+ "' are not matched");
					case '>' ://站定元素优先级高、计算双目运算
						//强制类型转换，若转换不成功则说明是变量
						try {
							secondDouTemp = Double.parseDouble(opnd.top());
						}
						catch (NumberFormatException e){
							if(opnd.top().equals(firstStr))
								secondDouTemp = firstDou;
							else if(opnd.top().equals(secondStr))
								secondDouTemp = secondDou;
							else if(opnd.top().equals(thirdStr))
								firstDouTemp = thirdDou;
							else
								throw new Exception ("the value of '" + opnd.top() 
														+ "' is not found");
						}
						opnd.pop();
						//强制类型转换，若转换不成功则说明是变量
						try {
							firstDouTemp = Double.parseDouble(opnd.top());
						}
						catch (NumberFormatException e){
							if(opnd.top().equals(firstStr))
								firstDouTemp = firstDou;
							else if(opnd.top().equals(secondStr))
								firstDouTemp = secondDou;
							else if(opnd.top().equals(thirdStr))
								firstDouTemp = thirdDou;
							else
								throw new Exception ("the value of '" + opnd.top() 
														+ "' is not found");
						}
						opnd.pop();
						if(optr.top().equals("+")){
							opnd.push(new Double(firstDouTemp + secondDouTemp).toString());	
						}
						else if(optr.top().equals("-")){
							opnd.push(new Double(firstDouTemp - secondDouTemp).toString());	
						}
						else if(optr.top().equals("*")){
							opnd.push(new Double(firstDouTemp * secondDouTemp).toString());	
						}
						else if(optr.top().equals("/")){
							if(secondDouTemp == 0)
								throw new Exception ("the second argument that '/' takes is 0");
							opnd.push(new Double(firstDouTemp / secondDouTemp).toString());	
						}
						else if(optr.top().equals("%")){
							if(secondDouTemp == 0)
								throw new Exception ("the second argument that '%' takes is 0");
							opnd.push(new Double(firstDouTemp % secondDouTemp).toString());	
						}
						else 
							throw new Exception ("the operator '" + optr.top() 
													+ "' is not supported");
						optr.pop();
						break;
				}
			}
		}
		result = Double.parseDouble(opnd.pop());
	}
	public Double getResult(){
		return result;
	}
	private String firstStr;//存储公式中第一个变量的表达式
	private String secondStr;//存储公式中第二个变量的表达式
	private String thirdStr;//存储公式中第三个变量的表达式
	private double firstDou;//存储公式中第一个变量的值
	private double secondDou;//存储公式中第二个变量的值
	private double thirdDou;//存储公式中第三个变量的值
	private double value1;//从构造函数接收过来的第一个变量得值
	private double value2;//从构造函数接收过来的第二个变量得值
	private double value3;//从构造函数接收过来的第三个变量得值
	
	private double firstDouTemp;//存储每次计算的第一个临时变量
	private double secondDouTemp;//存储每次计算的第二个变量
	private ElemList elemList = null;//链表头
	private ElemList current = null;//链表当前指针
	private int numOfParameter;	//公式中变量的个数
	private String expr;//存储公式
	private double result;//最终的计算结果
	//运算符
	private static final String [] keywords = 
	{
		"+","-","*","/","(",")","%","abs","acos","asin","atan","cbrt","ceil",
		"cos","cosh","exp","expm1","floor","log","log10","log1p","rint","round",
		"signum","sin","sinh","sqrt","tan","tanh","toDegrees","toRadians","#"	
	};
	//运算符优先级
	private static final char [] [] PRI =
	{		// +   -   *   /   (   )   %  abs acos asin atan cbrt ceil cos cosh exp expm1 floor log log10 log1p rint round signum sin sigh sprt tan tanh toDegrees toRadians #
   /*   +  */{'>','>','<','<','<','>','<','<', '<', '<','<', '<', '<', '<','<', '<','<',  '<',  '<','<',  '<',  '<', '<',  '<',   '<','<', '<', '<','<',   '<',      '<',   '>'},
   /*   -  */{'>','>','<','<','<','>','<','<', '<', '<','<', '<', '<', '<','<', '<','<',  '<',  '<','<',  '<',  '<', '<',  '<',   '<','<', '<', '<','<',   '<',      '<',   '>'},
   /*   *  */{'>','>','>','>','<','>','<','<', '<', '<','<', '<', '<', '<','<', '<','<',  '<',  '<','<',  '<',  '<', '<',  '<',   '<','<', '<', '<','<',   '<',      '<',   '>'},
   /*   /  */{'>','>','>','>','<','>','<','<', '<', '<','<', '<', '<', '<','<', '<','<',  '<',  '<','<',  '<',  '<', '<',  '<',   '<','<', '<', '<','<',   '<',      '<',   '>'},
   /*   (  */{'<','<','<','<','<','=','<','<', '<', '<','<', '<', '<', '<','<', '<','<',  '<',  '<','<',  '<',  '<', '<',  '<',   '<','<', '<', '<','<',   '<',      '<',   '@'},
   /*   )  */{'>','>','>','>','@','>','>','@', '@', '@','@', '@', '@', '@','@', '@','@',  '@',  '@','@',  '@',  '@', '@',  '@',   '@','@', '@', '@','@',   '@',      '@',   '>'},
   /*   %  */{'>','>','>','>','<','>','<','<', '<', '<','<', '<', '<', '<','<', '<','<',  '<',  '<','<',  '<',  '<', '<',  '<',   '<','<', '<', '<','<',   '<',      '<',   '>'},
   /*  abs */{'@','@','@','@','<','@','@','@', '@', '@','@', '@', '@', '@','@', '@','@',  '@',  '@','@',  '@',  '@', '@',  '@',   '@','@', '@', '@','@',   '@',      '@',   '@'},
   /* acos */{'@','@','@','@','<','@','@','@', '@', '@','@', '@', '@', '@','@', '@','@',  '@',  '@','@',  '@',  '@', '@',  '@',   '@','@', '@', '@','@',   '@',      '@',   '@'},
   /* asin */{'@','@','@','@','<','@','@','@', '@', '@','@', '@', '@', '@','@', '@','@',  '@',  '@','@',  '@',  '@', '@',  '@',   '@','@', '@', '@','@',   '@',      '@',   '@'},
   /* cbrt */{'@','@','@','@','<','@','@','@', '@', '@','@', '@', '@', '@','@', '@','@',  '@',  '@','@',  '@',  '@', '@',  '@',   '@','@', '@', '@','@',   '@',      '@',   '@'},
   /* ceil */{'@','@','@','@','<','@','@','@', '@', '@','@', '@', '@', '@','@', '@','@',  '@',  '@','@',  '@',  '@', '@',  '@',   '@','@', '@', '@','@',   '@',      '@',   '@'},
   /* acos */{'@','@','@','@','<','@','@','@', '@', '@','@', '@', '@', '@','@', '@','@',  '@',  '@','@',  '@',  '@', '@',  '@',   '@','@', '@', '@','@',   '@',      '@',   '@'},
   /*  cos */{'@','@','@','@','<','@','@','@', '@', '@','@', '@', '@', '@','@', '@','@',  '@',  '@','@',  '@',  '@', '@',  '@',   '@','@', '@', '@','@',   '@',      '@',   '@'},
   /*  cos */{'@','@','@','@','<','@','@','@', '@', '@','@', '@', '@', '@','@', '@','@',  '@',  '@','@',  '@',  '@', '@',  '@',   '@','@', '@', '@','@',   '@',      '@',   '@'},
   /*  exp */{'@','@','@','@','<','@','@','@', '@', '@','@', '@', '@', '@','@', '@','@',  '@',  '@','@',  '@',  '@', '@',  '@',   '@','@', '@', '@','@',   '@',      '@',   '@'},
   /* expm1*/{'@','@','@','@','<','@','@','@', '@', '@','@', '@', '@', '@','@', '@','@',  '@',  '@','@',  '@',  '@', '@',  '@',   '@','@', '@', '@','@',   '@',      '@',   '@'},
   /* floor*/{'@','@','@','@','<','@','@','@', '@', '@','@', '@', '@', '@','@', '@','@',  '@',  '@','@',  '@',  '@', '@',  '@',   '@','@', '@', '@','@',   '@',      '@',   '@'},
   /*  log */{'@','@','@','@','<','@','@','@', '@', '@','@', '@', '@', '@','@', '@','@',  '@',  '@','@',  '@',  '@', '@',  '@',   '@','@', '@', '@','@',   '@',      '@',   '@'},
   /* log10*/{'@','@','@','@','<','@','@','@', '@', '@','@', '@', '@', '@','@', '@','@',  '@',  '@','@',  '@',  '@', '@',  '@',   '@','@', '@', '@','@',   '@',      '@',   '@'},
   /* log1p*/{'@','@','@','@','<','@','@','@', '@', '@','@', '@', '@', '@','@', '@','@',  '@',  '@','@',  '@',  '@', '@',  '@',   '@','@', '@', '@','@',   '@',      '@',   '@'},
   /*  rint*/{'@','@','@','@','<','@','@','@', '@', '@','@', '@', '@', '@','@', '@','@',  '@',  '@','@',  '@',  '@', '@',  '@',   '@','@', '@', '@','@',   '@',      '@',   '@'},
   /* round*/{'@','@','@','@','<','@','@','@', '@', '@','@', '@', '@', '@','@', '@','@',  '@',  '@','@',  '@',  '@', '@',  '@',   '@','@', '@', '@','@',   '@',      '@',   '@'},
   /*signum*/{'@','@','@','@','<','@','@','@', '@', '@','@', '@', '@', '@','@', '@','@',  '@',  '@','@',  '@',  '@', '@',  '@',   '@','@', '@', '@','@',   '@',      '@',   '@'},
   /*  sin */{'@','@','@','@','<','@','@','@', '@', '@','@', '@', '@', '@','@', '@','@',  '@',  '@','@',  '@',  '@', '@',  '@',   '@','@', '@', '@','@',   '@',      '@',   '@'},
   /* sinh */{'@','@','@','@','<','@','@','@', '@', '@','@', '@', '@', '@','@', '@','@',  '@',  '@','@',  '@',  '@', '@',  '@',   '@','@', '@', '@','@',   '@',      '@',   '@'},
   /*  sprt*/{'@','@','@','@','<','@','@','@', '@', '@','@', '@', '@', '@','@', '@','@',  '@',  '@','@',  '@',  '@', '@',  '@',   '@','@', '@', '@','@',   '@',      '@',   '@'},
   /*  tan */{'@','@','@','@','<','@','@','@', '@', '@','@', '@', '@', '@','@', '@','@',  '@',  '@','@',  '@',  '@', '@',  '@',   '@','@', '@', '@','@',   '@',      '@',   '@'},
   /*  tanh*/{'@','@','@','@','<','@','@','@', '@', '@','@', '@', '@', '@','@', '@','@',  '@',  '@','@',  '@',  '@', '@',  '@',   '@','@', '@', '@','@',   '@',      '@',   '@'},
/*toDegrees*/{'@','@','@','@','<','@','@','@', '@', '@','@', '@', '@', '@','@', '@','@',  '@',  '@','@',  '@',  '@', '@',  '@',   '@','@', '@', '@','@',   '@',      '@',   '@'},
/*toRadians*/{'@','@','@','@','<','@','@','@', '@', '@','@', '@', '@', '@','@', '@','@',  '@',  '@','@',  '@',  '@', '@',  '@',   '@','@', '@', '@','@',   '@',      '@',   '@'},
   /*   #  */{'<','<','<','<','<','@','<','<', '<', '<','<', '<', '<', '<','<', '<','<',  '<',  '<','<',  '<',  '<', '<',  '<',   '<','<', '<', '<','<',   '<',      '<',   '='}
	};
}

//将公式中关键字和其他量分开存放的链式结构
class ElemList {
	ElemList (String value) {
		data = value;	
	}	
	ElemList next;
	String data;
	boolean isOperator;
}

//Stack类中用到的链式结构
class ListElement {
	ListElement (String value){
		data = value;
	}
	ListElement next;
	String data;	
}

//--栈类
class Stack{
	//返回栈顶元素的data域
	public String top(){
		if(top != null)
			return top.data;
		else
			return null;	
	}	
	//将新元素压入栈
	public void push(String value){
		if(top == null)
			top = new ListElement(value);	
		else{
			ListElement temp = new ListElement(value);
			temp.next = top;
			top = temp;	
		}
	}
	//弹出栈顶元素并返回其data域
	public String pop(){
		String result = top();
		if(top != null)
			top = top.next;
		return result;	
	}
	//判断栈是否为空
	public boolean empty(){
		return top == null;	
	}
	private ListElement top = null;
}