Java计算器实现(逆波兰式)

package hfw.util;import java.util.ArrayDeque;import java.util.Deque;/****逆波兰式*总结，java版的Eval：逆波兰和动态编译，推荐用动态编译，因为逆波兰式不认识"- 4"，只认识"-4"*@author zyh*/public class RNP {/*** 运算数*/private static Deque<String> operationNum = new ArrayDeque<String>();/*** 运算符*/private static Deque<String> operator = new ArrayDeque<String>();/*** 将表达式转换为逆波兰式* @param expression* @return*/private static void str2Rnp(String expression){operationNum.clear();operator.clear();int index = 0;for(int i=0;i<expression.length();i++){char c = expression.charAt(i);if(isOperator(c) || c=='(' || c==')'){//操作数直接入栈String operationNum = expression.substring(index,i);//区分负号和减号,如果'-'前面的一个是+-*/( 认为是负号,'-'前面的是数或)认为是减号if(c=='-'){int in = i;while((expression.charAt(in-1)) ==' '){in--;if(in==0){break;}}if(in==0){continue;}String previous = expression.substring(in-1,i);if(isOperator(previous.charAt(0)) || previous.charAt(0)=='('){continue;}}if(operationNum.trim().length()>0){RNP.operationNum.push(operationNum.trim());}index = i+1;String operator = c+"";//如果操作符是'('，直接入栈if('('==c){RNP.operator.push(operator);//如果操作符是')'，将'('操作符之后的全部出栈，入栈操作数，'(' ')'舍弃}else if(')'==c){while(true){String o = RNP.operator.pollFirst();if(o==null || "(".equals(o)){break;}RNP.operationNum.push(o);}//如果操作符是+-*/}else{String o = RNP.operator.peekFirst();if(o== null){//如果操作符栈为空，操作符直接入栈RNP.operator.push(operator);}else {char operator2 = o.charAt(0);//比较操作符，和操作符栈首的大小，如果操作符大，直接入栈if(operator2=='(' || operator2==')' || orderOperator(c,operator2)){RNP.operator.push(operator);//如果操作符栈首大，将操作符栈小于操作符的全部出栈，入栈操作数，最后改操作符入栈}else{while(true){if(o==null || o.charAt(0) =='('|| o.charAt(0) ==')'){break;}if(orderOperator(c, o.charAt(0))){break;}o = RNP.operator.pollFirst();RNP.operationNum.push(o);o = RNP.operator.peekFirst();}RNP.operator.push(operator);}}}}}String operationNum = expression.substring(index);if(operationNum.trim().length()>0){RNP.operationNum.push(operationNum.trim());}while(RNP.operator.size()>0){RNP.operationNum.push(RNP.operator.pollFirst());}// RNP.operationNum.addAll(RNP.operator);}//判断一个字符是否为运算符private static boolean isOperator(char c) {return c=='+' || c=='-' || c=='*' || c=='/';}//判断运算符顺序，true表示运算符operator1>operator2,false表示相等或小于private static boolean orderOperator(char operator1, char operator2){if((operator1=='*' || operator1=='/') && (operator2=='+' || operator2=='-')){ return true;}return false;}/*** 计算逆波兰式的值* @return*/private static double countRnp(){while(RNP.operationNum.size()>0){String s = RNP.operationNum.pollLast();//如果是操作符，取出栈顶的两个操作数，直接运算char operator = s.charAt(0);if(s.length()==1 && isOperator(operator)){String a = RNP.operator.pollFirst();String b = RNP.operator.pollFirst();if('+'==operator){double result = Double.parseDouble(b)+Double.parseDouble(a);RNP.operator.push(result+"");}else if('-'==operator){double result = Double.parseDouble(b)-Double.parseDouble(a);RNP.operator.push(result+"");}if('*'==operator){double result = Double.parseDouble(b)*Double.parseDouble(a);RNP.operator.push(result+"");}if('/'==operator){double result = Double.parseDouble(b)/Double.parseDouble(a);RNP.operator.push(result+"");}//如果是操作数，入栈}else{RNP.operator.push(s);}}double result = Double.parseDouble(RNP.operator.pollLast());return result;}/*** 计算逆波兰式的值(整数)* @return*/private static int intRnp(){while(RNP.operationNum.size()>0){String s = RNP.operationNum.pollLast();//如果是操作符，取出栈顶的两个操作数，直接运算char operator = s.charAt(0);if(s.length()==1 && isOperator(operator)){String a = RNP.operator.pollFirst();String b = RNP.operator.pollFirst();if('+'==operator){int result = Integer.parseInt(b)+Integer.parseInt(a);RNP.operator.push(result+"");}else if('-'==operator){int result = Integer.parseInt(b)-Integer.parseInt(a);RNP.operator.push(result+"");}if('*'==operator){int result = Integer.parseInt(b)*Integer.parseInt(a);RNP.operator.push(result+"");}if('/'==operator){int result = Integer.parseInt(b)/Integer.parseInt(a);RNP.operator.push(result+"");}//如果是操作数，入栈}else{RNP.operator.push(s);}}int result = Integer.parseInt(RNP.operator.pollLast());return result;}/*** 计算表达式的值* @param expression* @return*/public static double calculate(String expression){try{str2Rnp(expression);return countRnp();}catch(Exception e){e.printStackTrace();System.out.println("请检查表达式");return 0.0;}}/*** 计算表达式的值(整数)* @param expression* @return*/public static int intCalculate(String expression){try{str2Rnp(expression);return intRnp();}catch(Exception e){e.printStackTrace();System.out.println("请检查表达式");return 0;}}public static void main(String[] args) {String s= "53.12* 6/ ( -12-7.2)* -6 *( -4)*12*6/7.2-6";System.out.println(RNP.calculate(s));s = "((( -1+ 2 ) * -2) * -4)-9*( -1 + 2)";System.out.println(RNP.intCalculate(s));}}。