JAVA 算术运算

最新推荐文章于 2024-02-25 00:15:00 发布

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本文介绍了一种使用栈数据结构实现的表达式求值算法，该算法能够解析并计算包含括号、加减乘除运算符及整数的数学表达式。

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class GenericStack {
private java.util.ArrayList list=new java.util.ArrayList();

public int getSize(){
   return list.size();
}

public E peek(){

   return list.get(getSize()-1);
}

public void push(E o){
   list.add(o);
}
public E pop(){
   E o=list.get(getSize()-1);
   list.remove(getSize()-1);
   return o;
}

public boolean isEmpty()
{
   return list.isEmpty();
}
}
public class EvaluateExpression{
    public static void main(String[] args){
    String expression="(3-2)*6+9/3";
      try{
       System.out.println(expression+"="+evaluateexpression_r(expression));
   }catch(Exception ex){
     System.out.println("wrong expression!");
    }
    }


    public static int evaluateexpression_r(String expression){

      GenericStackoperandStack=new GenericStack();

   GenericStackoperatiorStack=new GenericStack();

   java.util.StringTokenizer tokens=new java.util.StringTokenizer(expression,"()+-/*",true);
   while(tokens.hasMoreTokens())
   {
      String token=tokens.nextToken().trim();
     // System.out.println(token);
   if(token.length()==0){
   continue;
   }
   else if(token.charAt(0)=='+'||token.charAt(0)=='-'){
     while(!operatiorStack.isEmpty() &&(operatiorStack.peek()=='+'||
     operatiorStack.peek()=='-'||
     operatiorStack.peek()=='*'||
     operatiorStack.peek()=='/'))
     {
      processAnOperator(operandStack,operatiorStack);
     }
     operatiorStack.push(token.charAt(0));
   }
   else if(token.charAt(0)=='*'|| token.charAt(0)=='/'){
     while(!operatiorStack.isEmpty() &&(
     operatiorStack.peek()=='*'||
     operatiorStack.peek()=='/')){
      processAnOperator(operandStack,operatiorStack);
     }
     operatiorStack.push(token.charAt(0));
   }
   else if(token.trim().charAt(0)=='('){
    operatiorStack.push('(');
   }
    else if(token.trim().charAt(0)==')'){
      while(operatiorStack.peek()!='('){
      processAnOperator(operandStack,operatiorStack);
      }
      operatiorStack.pop();
   }
   else{
    operandStack.push(new Integer(token));
   }
   }

   while(!operatiorStack.isEmpty()){
     processAnOperator(operandStack,operatiorStack);
   }
   return operandStack.pop();
    }

    public static void processAnOperator(GenericStack operandStack,GenericStackoperatiorStack){
       char op=operatiorStack.pop();
    int op1=operandStack.pop();
    int op2=operandStack.pop();
    if(op=='+')
    operandStack.push(op2+op1);
    if(op=='-')
    operandStack.push(op2-op1);
    if(op=='*')
    operandStack.push(op2*op1);
    if(op=='/')
    operandStack.push(op2/op1);
    }
}