java實現(xiàn)字符串四則運算公式解析工具類的方法

package org.nercita.bcp.record.util;
 
import java.util.ArrayList;
import java.util.LinkedList;
 
/**
 * @author zhangwenchao
 * @since 2016-08-26
 * 公式計算的工具類
 */
public class FormulaCalculator {
	
	private static boolean isRightFormat = true;
 
	public static double getResult(String formula){ 
		double returnValue = 0; 
		try{ 
			returnValue = doAnalysis(formula); 
		}catch(NumberFormatException nfe){ 
			System.out.println("公式格式有誤，請檢查:" + formula); 
		}catch(Exception e){ 
			e.printStackTrace(); 
		} 
		if(!isRightFormat){ 
			System.out.println("公式格式有誤，請檢查:" + formula); 
		} 
		return returnValue;	
	}
 
	private static double doAnalysis(String formula){
		double returnValue = 0; 
		LinkedList<Integer> stack = new LinkedList<Integer>(); 
		int curPos = 0; 
		String beforePart = ""; 
		String afterPart = ""; 
		String calculator = ""; 
		isRightFormat = true; 
		while(isRightFormat&&(formula.indexOf('(') >= 0||formula.indexOf(')') >= 0)){			
			curPos = 0; 
			for(char s : formula.toCharArray()){ 
				if(s == '('){  
					stack.add(curPos); 
				}else if(s == ')'){  
					if(stack.size() > 0){  
						beforePart = formula.substring(0, stack.getLast());  
						afterPart = formula.substring(curPos + 1);  
						calculator = formula.substring(stack.getLast() + 1, curPos);  
						formula = beforePart + doCalculation(calculator) + afterPart;  
						stack.clear();  
						break;  
					}else{  
						System.out.println("有未關(guān)閉的右括號！");  
						isRightFormat = false;  
					} 
				} 
				curPos++; 
			} 
			if(stack.size() > 0){ 
				System.out.println("有未關(guān)閉的左括號！"); 
				break; 
			} 
		} 
		if(isRightFormat){ 
			returnValue = doCalculation(formula); 
		} 
		return returnValue; 
	}
 	
	private static double doCalculation(String formula) { 
		ArrayList<Double> values = new ArrayList<Double>(); 
		ArrayList<String> operators = new ArrayList<String>(); 
		int curPos = 0; 
		int prePos = 0;
		int minus = 0;		
		for (char s : formula.toCharArray()) { 
			 if ((s == '+' || s == '-' || s == '*' || s == '/') && minus !=0 && minus !=2) { 								 			 
				 values.add(Double.parseDouble(formula.substring(prePos, curPos).trim())); 				
				 operators.add("" + s); 				
				 prePos = curPos + 1;				 
				 minus = minus +1;
			 }else{				 
				 minus =1;				 
			 }
			 curPos++; 		
		} 
		values.add(Double.parseDouble(formula.substring(prePos).trim())); 
		char op; 
		for (curPos = 0; curPos <= operators.size() - 1; curPos++) {							
			op = operators.get(curPos).charAt(0); 
			switch (op) { 
			case '*': 
				values.add(curPos, values.get(curPos) * values.get(curPos + 1)); 
				values.remove(curPos + 1); 
				values.remove(curPos + 1); 
				operators.remove(curPos); 
				curPos = -1;
				break; 
			case '/': 
				values.add(curPos, values.get(curPos) / values.get(curPos + 1)); 
				values.remove(curPos + 1); 
				values.remove(curPos + 1); 
				operators.remove(curPos); 
				curPos = -1;
				break; 
			} 
		} 
		for (curPos = 0; curPos <= operators.size() - 1; curPos++) { 
			op = operators.get(curPos).charAt(0); 
			switch (op) { 
			case '+': 
				values.add(curPos, values.get(curPos) + values.get(curPos + 1)); 
				values.remove(curPos + 1); 
				values.remove(curPos + 1); 
				operators.remove(curPos); 
				curPos = -1;
				break; 
			case '-': 
				values.add(curPos, values.get(curPos) - values.get(curPos + 1)); 
				values.remove(curPos + 1); 
				values.remove(curPos + 1); 
				operators.remove(curPos); 
				curPos = -1;
				break; 
			} 
		} 
		return values.get(0).doubleValue();
	}
 
	public static void main(String[] args) {	 
		System.out.println(FormulaCalculator.getResult("3-(4*5)+5"));	
		System.out.println(FormulaCalculator.getResult("7/2-(-4)"));			
		System.out.println(FormulaCalculator.getResult("1287763200000-1276272000000")/(3600*24*1000));
	}
	
}

package org.nercita.bcp.record.util;
 
import java.text.DecimalFormat;
 
/**
 
 * @author zhangwenchao
 * 小數(shù)點 精度的工具類
 */ 
public class SetNumberPrecision {
		
	public static String setNumberPrecision(double x,int Number){		 
		String p="#########0";		 
		if(Number==0){			 
			p="#########0";		 
		}else{		  
			p="#########0.";		  
			for(int i=0;i<Number;i++){//for的巧妙運用		   
				p=p+"0"; 		  
			}		 
		}		  
		DecimalFormat f = new DecimalFormat(p); 		  
		String s = f.format(x).toString(); 		  
		return s;		 
	}
	
}