int形式的字符串方程式答案

-2

我在一個低級別的java類中，我需要使用java和JavaScript製作應用程序。我決定創建一個使用加法，減法，乘法和除法創建隨機方程的遊戲。我遇到的麻煩是我的等式是以字符串的形式創建的，我需要能夠計算答案以將其與用戶答案進行比較。我認爲我有一個解決我的問題的後裔解決方案，但我不斷收到一些問題。你能幫我嗎？我的代碼如下：int形式的字符串方程式答案

import java.util.*; 
public class GameClient { 

    private static Stack<String> operations; 
    private static Stack<Integer> numbers; 
    private static String[] tokens; 
    private static int i; 
    private static Stack<String> subAdd; 
    private static Stack<Integer> restOfNumbers; 

    public static void main(String[] args) { 
     Random variable = new Random(); 
     int numberOfVariables = variable.nextInt(5)+2;  //determines length of equation 
     String equation = ""; 
     equation = equationGenerator(equation, numberOfVariables, variable); 
     System.out.println(equation); 
     System.out.print(calculateAnswer(equation)); 

    } 
    public static String equationGenerator(String equation, int numberOfVariables, Random variable){ 
     int operation; 
     int var; 

     var = variable.nextInt(10)+1; 

     equation += var; 
     operation = variable.nextInt(4)+1; 

     if(numberOfVariables == 1){ 
      equation += " = "; 
      return equation; 
     } 

     if(operation == 1) 
     { 
      equation += " + "; 
     } 
     else if(operation == 2) 
     { 
      equation += " - "; 
     } 
     else if(operation == 3) 
     { 
      equation += "/"; 
     } 
     else if(operation == 4) 
     { 
      equation += " * "; 
     } 

     return equationGenerator(equation, numberOfVariables-1, variable); 
    } 

    public static int calculateAnswer(String equation){ 
     String delims = "[ ]+"; 
     tokens = equation.split(delims); 
     for(i=0; i< tokens.length; i++)      //does all multiplication and division first leaving just addition and subtraction 
      switch(tokens[i]){ 
      case "0": case "1":case "2":case "3":case "4":case "5":case "6":case "7":case "8":case "9": 
       int number = Integer.parseInt(tokens[i]); 
       popOrPush(number); 
       break; 
      case "*": case "/": case "+": case "-": 
       popOrPush(tokens[i], tokens); 
      } 

     while(!numbers.empty()){     //flips number and operation stacks to do addition and subtraction in correct order 
      restOfNumbers.push(numbers.pop()); 
     } 
     while(!operations.empty()){ 
      subAdd.push(operations.pop()); 
     } 
     while(!subAdd.empty()){ 
      switch(subAdd.pop()){ 
      case "+": 
       restOfNumbers.push(restOfNumbers.pop() + restOfNumbers.pop()); 
      case "-": 
       restOfNumbers.push(restOfNumbers.pop() - restOfNumbers.pop()); 
      } 
     } 
     return restOfNumbers.pop(); 
    } 

    public static void popOrPush(int number){ 
     numbers.push(number); 
    } 
    public static void popOrPush(String operation, String[] tokens){ 
     switch(operation){ 
     case "*": 
      int multipliedValue = numbers.pop(); 
      i++; 
      multipliedValue = multipliedValue * Integer.parseInt(tokens[i]); 
      numbers.push(multipliedValue); 
     case "/": 
      int dividedValue = numbers.pop(); 
      i++; 
      dividedValue = dividedValue/Integer.parseInt(tokens[i]); 
      numbers.push(dividedValue); 
     case "+": case "-": 
      operations.push(operation); 
    } 
    } 
}

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2017-05-07 boydf

那麼，它是java還是javascript？因爲我有消息給你，它不能同時存在。（爲什麼添加標籤時不知道它是什麼意思？） –

如果是Java，請查看[this]（http://stackoverflow.com/questions/3422673/evaluating-a-math-expression -given-in-string-form）SO答案。 –

這是Java而不是Javascript。 – sydluce

你沒有初始化的籌碼，所以你要使用numbers變量時可能會得到一個NPE。

確保初始化所有變量（特別是您的堆棧對象）。例如：

Stack<Integer> numbers = new Stack<>();

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2017-05-07 22:05:32 Rohan

int形式的字符串方程式答案

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