evaluating postfix expression in java

Harith Dzikri answered on December 1, 2022 Popularity 5/10 Helpfulness 3/10

answer evaluating postfix expression in java

evaluating postfix expression in java

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import java.util.*;
 
public class PostfixEvaluation
{
 
  static boolean isOperator(char ch)
  {
      if(ch == '+' || ch == '-' || ch == '*' || ch == '/')
      return true;
      
      return false;
  }
    
  static void evaluatePostfix(String exp)
  {
      Stack<Integer> postFix = new Stack<>();    // Create postfix stack
      int n = exp.length();
      
      for(int i=0;i<n;i++)
      {
        if(isOperator(exp.charAt(i)))
        {
        // pop top 2 operands.
        int op1 = postFix.pop();
        int op2 = postFix.pop();
              
        // evaluate in reverse order i.e. op2 operator op1.
        switch(exp.charAt(i))
        {
            case '+': postFix.push(op2 + op1);
                      break;
                      
            case '-': postFix.push(op2 - op1);
                      break;
                      
            case '*': postFix.push(op2 * op1);
                      break;
                
            case '/': postFix.push(op2 / op1);
                      break;
                    
        }
        
        }
        // Current Char is Operand simple push into stack
        else
        {
        // convert to integer
        int operand = exp.charAt(i) - '0';
        postFix.push(operand);
        }
      }
      
      // Stack at End will contain result.
      System.out.println(postFix.pop());
  }
  
  public static void main(String args[])
  {
      String exp = "823*+7/1-";
      System.out.print("The PostFix Evaluation for the Given Expression "+exp+" is: ");
      evaluatePostfix(exp);
  }
    
}

Popularity 5/10 Helpfulness 3/10 Language java

Source: www.thejavaprogrammer.com

Tags: expression java postfix

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Contributed on Dec 01 2022

Harith Dzikri

0 Answers Avg Quality 2/10

evaluating postfix expression in java

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