Arithmetic Expression Evaluation in j2me: Works only for single digit operands

Question

I have implemented the algorithm that I have found on this link to evaluate an arithmetic expression for j2me. But it works fine only when I have single digit operands i.e. 2, 5, 7, 3 but not for 456, 56, 34.45 etc. I did some changes as i knew i had to add the numbers found not one by one but till we end with a digit. Then I found this link also but still things didn't go well as expected. First I had tried the exp4j library but I guess that does not work on j2me. The code has become very messy right now. Could I get any opinions on how should I go about this problem? Any help on this would be appreciated.

Code that initially worked only for single digit operands:

import java.util.Stack;
import java.util.Vector;
import java.util.logging.Level;
import java.util.logging.Logger;

public class SampleInfixToPostfixToResult {

static Stack stack=new Stack();
static StringBuffer p=new StringBuffer();
static Vector v=new Vector();

public static StringBuffer toPostfix(String q)
{
for(int i=0;i<q.length();i++)
{
    if(q.charAt(i)=='0'||q.charAt(i)=='1'||q.charAt(i)=='2'||q.charAt(i)=='3'||q.charAt(i)=='4'||q.charAt(i)=='5'||q.charAt(i)=='6'||q.charAt(i)=='7'||q.charAt(i)=='8'||q.charAt(i)=='9')
    {
        p.append(q.charAt(i));
    }
    else if(q.charAt(i)=='(')
    {
         stack.push(q.charAt(i));
    }
    else if(q.charAt(i)==')')
    {
        for(int j=0;!stack.empty()&&!stack.peek().equals('(');j++)
        {
            p.append(stack.pop());
        }
        stack.pop();
    }
    else if(q.charAt(i)=='+'||q.charAt(i)=='-'||q.charAt(i)=='/'||q.charAt(i)=='*')
    {
        if(stack.empty()||stack.peek().equals('('))
            stack.push(q.charAt(i));
        else
        {
            while(!stack.empty()&&!stack.peek().equals('(')&&isHigh(q.charAt(i), stack.peek()))
            {
                p.append(stack.pop());
            }
            stack.push(q.charAt(i));
        }
    }
}
while(!stack.empty())
{
    p.append(stack.pop());
}
System.out.println(p);
return p;
}


public static boolean isHigh(char op, Object AtStack)
{
char opAtStack=AtStack.toString().charAt(0);
boolean isHigh=false;
if((op==opAtStack))
    isHigh=true;
if((op=='+'||op=='-')&&(opAtStack=='/'||opAtStack=='*'))
{
    isHigh=true;
}
if((op=='+'&&opAtStack=='-')||(op=='-'&&opAtStack=='+')||(op=='/'&&opAtStack=='*')||(op=='*'&&opAtStack=='/'))
{
    isHigh=true;
}
    return isHigh;
}

public static double result(StringBuffer p)
{

for(int i=0;i<p.length();i++)
{
    System.out.println(p.charAt(i));
    if(p.charAt(i)=='0'||p.charAt(i)=='1'||p.charAt(i)=='2'||p.charAt(i)=='3'||p.charAt(i)=='4'||p.charAt(i)=='5'||p.charAt(i)=='6'||p.charAt(i)=='7'||p.charAt(i)=='8'||p.charAt(i)=='9')
    {
        stack.push(p.charAt(i));
    }
    if(p.charAt(i)=='+'||p.charAt(i)=='-'||p.charAt(i)=='/'||p.charAt(i)=='*')
    {
        double a=Double.parseDouble(stack.pop().toString());
        double b=Double.parseDouble(stack.pop().toString());
        if(p.charAt(i)=='+')
        {
            stack.push(b+a);
        }
        else if(p.charAt(i)=='-')
        {
            stack.push(b-a);
        }
        else if(p.charAt(i)=='/')
        {
            stack.push(b/a);
        }
        else if(p.charAt(i)=='*')
        {
            stack.push(b*a);
        }
    }
}
System.out.println(stack);
return 0;
}

public static void main(String[] args) {
    // TODO code application logic here
    String s=new String("65*(76+2)-0/4+(2*5-6*(2*5))");


    SampleInfixToPostfixToResult.result(SampleInfixToPostfixToResult.toPostfix(s));
    System.out.println(66*(76+2)-0/4+(2*5-6*(2*5)));
}
}

Updated code that I worked on for evaluation of multi-digit operand (really messed up)

import java.util.Stack;
import java.util.Vector;
import java.util.logging.Level;
import java.util.logging.Logger;

public class SampleInfixToPostfixToResult {

static Stack stack=new Stack();
static StringBuffer p=new StringBuffer();
static Vector v=new Vector();

public static Vector toPostfix(String q) 
{
for(int i=0;i<q.length();i++)
{
    if(q.charAt(i)=='0'||q.charAt(i)=='1'||q.charAt(i)=='2'||q.charAt(i)=='3'||q.charAt(i)=='4'||q.charAt(i)=='5'||q.charAt(i)=='6'||q.charAt(i)=='7'||q.charAt(i)=='8'||q.charAt(i)=='9')
    {
        StringBuffer tn=new StringBuffer();
        while(i<q.length()&&(q.charAt(i)=='0'||q.charAt(i)=='1'||q.charAt(i)=='2'||q.charAt(i)=='3'||q.charAt(i)=='4'||q.charAt(i)=='5'||q.charAt(i)=='6'||q.charAt(i)=='7'||q.charAt(i)=='8'||q.charAt(i)=='9'))
        {
             tn.append(q.charAt(i++));
        }

        v.add(tn);

    }
    else if(q.charAt(i)=='(')
    {
         stack.push(q.charAt(i));
    }
    else if(q.charAt(i)==')')
    {
        for(int j=0;!stack.empty()&&!stack.peek().equals('(');j++)
        {
            v.add(stack.pop());
        }
        stack.pop();
    }
    else if(q.charAt(i)=='+'||q.charAt(i)=='-'||q.charAt(i)=='/'||q.charAt(i)=='*')
    {
        if(stack.empty()||stack.peek().equals('('))
            stack.push(q.charAt(i));
        else
        {
            while(!stack.empty()&&!stack.peek().equals('(')&&isHigh(q.charAt(i), stack.peek()))
            {
                v.add(stack.pop());
            }
            stack.push(q.charAt(i));
        }
    }
}
while(!stack.empty())
{
    v.add(stack.pop());
}

return v;
}

public static boolean isHigh(char op, Object AtStack)
{
char opAtStack=AtStack.toString().charAt(0);
boolean isHigh=false;
if((op==opAtStack))
    isHigh=true;
if((op=='+'||op=='-')&&(opAtStack=='/'||opAtStack=='*'))
{
    isHigh=true;
}
if((op=='+'&&opAtStack=='-')||(op=='-'&&opAtStack=='+')||(op=='/'&&opAtStack=='*')||(op=='*'&&opAtStack=='/'))
{
    isHigh=true;
}
    return isHigh;
}

public static double result(Vector p)
{

for(int i=0;i<p.size();i++)
{
    System.out.println(p.get(i));
    if(p.get(i)=="0"||p.get(i)=="1"||p.get(i)=="2"||p.get(i)=="3"||p.get(i)=="4"||p.get(i)=="5"||p.get(i)=="6"||p.get(i)=="7"||p.get(i)=="8"||p.get(i)=="9")
    {
         StringBuffer tn=new StringBuffer();
        while(i<p.size()&&(p.get(i)=="0"||p.get(i)=="1"||p.get(i)=="2"||p.get(i)=="3"||p.get(i)=="4"||p.get(i)=="5"||p.get(i)=="6"||p.get(i)=="7"||p.get(i)=="8"||p.get(i)=="9"))
        {
             tn.append(p.get(i++));
        }
        System.out.println("This is the full number :"+tn);
        stack.push(tn);
    }
    if(p.get(i)=="+"||p.get(i)=="-"||p.get(i)=="/"||p.get(i)=="*")
    {
        double a=Double.parseDouble(stack.pop().toString());
        double b=Double.parseDouble(stack.pop().toString());
        if(p.get(i)=="+")
        {
            stack.push(b+a);
        }
        else if(p.get(i)=="-")
        {
            stack.push(b-a);
        }
        else if(p.get(i)=="/")
        {
            stack.push(b/a);
        }
        else if(p.get(i)=="*")
        {
            stack.push(b*a);
        }
    }
}
System.out.println("Final value: "+stack);
return 0;
}

public static void main(String[] args) {
    // TODO code application logic here
    String s=new String("65*(79+22)-0/4+(29*5-6*(2*5))");

    SampleInfixToPostfixToResult.result(SampleInfixToPostfixToResult.toPostfix(s));
    //System.out.println(65*(79+22)-0/4+(29*5-6*(2*5)));
}
}

You might find [`Character#isDigit`](http://docs.oracle.com/javase/7/docs/api/java/lang/Character.html#isDigit(char)) helpful, along with `Set#contains` for your operators. — chrylis -cautiouslyoptimistic-, Aug 16 '13 at 06:27

Nitesh Verma · Accepted Answer · 2013-08-21T05:31:56.470

Solution:

1.Function toPostfix() now returns stack instead of vector, as now the postfix expression is added to the stack eg, [34,57.+] etc.

2.Edited the code for storing all the digits to the stack by traversing the string till we have a number.(see code till line no 29)

import java.util.Stack;
import java.util.Vector;

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */

/**
 *
 * @author Sandeep
 */
public class Main {
    static Stack stack=new Stack();
    static Stack stackT=new Stack();
    //static Vector v=new Vector();
    //static StringBuffer p=new StringBuffer();

    public static Stack toPostfix(String q)
{

    for(int i=0;i<q.length();i++)
    {   
        if(q.charAt(i)=='0'||q.charAt(i)=='1'||q.charAt(i)=='2'||q.charAt(i)=='3'||q.charAt(i)=='4'||q.charAt(i)=='5'||q.charAt(i)=='6'||q.charAt(i)=='7'||q.charAt(i)=='8'||q.charAt(i)=='9')
        {
            StringBuffer p=new StringBuffer();
            while(q.charAt(i)=='0'||q.charAt(i)=='1'||q.charAt(i)=='2'||q.charAt(i)=='3'||q.charAt(i)=='4'||q.charAt(i)=='5'||q.charAt(i)=='6'||q.charAt(i)=='7'||q.charAt(i)=='8'||q.charAt(i)=='9')
                    p.append(q.charAt(i++));
            stackT.push(p);
            i--;
        }
        else if(q.charAt(i)=='(')
        {
             stack.push(q.charAt(i));
        }
        else if(q.charAt(i)==')')
        {
            for(int j=0;!stack.empty()&&!stack.peek().equals('(');j++)
            {
                stackT.push(stack.pop().toString());
            }
            stack.pop();
        }
        else if(q.charAt(i)=='+'||q.charAt(i)=='-'||q.charAt(i)=='/'||q.charAt(i)=='*')
        {
            if(stack.empty()||stack.peek().equals('('))
                stack.push(q.charAt(i));
            else
            {
                while(!stack.empty()&&!stack.peek().equals('(')&&isHigh(q.charAt(i), stack.peek()))
                {
                    stackT.push(stack.pop().toString());
                }
                stack.push(q.charAt(i));
            }
        }
    }
   while(!stack.empty())
    {
        stackT.push(stack.pop().toString());
    }

       System.out.println(stackT);
    return stackT;
}

//problem lies here
public static boolean isHigh(char op, Object AtStack)
{
    char opAtStack=AtStack.toString().charAt(0);
    boolean isHigh=false;
    if((op==opAtStack))
        isHigh=true;
    if((op=='+'||op=='-')&&(opAtStack=='/'||opAtStack=='*'))
    {
        isHigh=true;
    }
    if((op=='+'&&opAtStack=='-')||(op=='-'&&opAtStack=='+')||(op=='/'&&opAtStack=='*')||(op=='*'&&opAtStack=='/'))
    {
        isHigh=true;
    }
        return isHigh;
}

public static double result(Stack p)
{

    for(int i=0;i<p.size();i++)
    {   
        if(p.get(i).toString().startsWith("0")||p.get(i).toString().startsWith("1")||p.get(i).toString().startsWith("2")||p.get(i).toString().startsWith("3")||p.get(i).toString().startsWith("4")||p.get(i).toString().startsWith("5")||p.get(i).toString().startsWith("6")||p.get(i).toString().startsWith("7")||p.get(i).toString().startsWith("8")||p.get(i).toString().startsWith("9"))
        {
            stack.push(p.get(i));
        }
        if(p.get(i).toString().equals("+")||p.get(i).toString().equals("-")||p.get(i).toString().equals("/")||p.get(i).toString().equals("*"))
        {
            double a=Double.parseDouble(stack.pop().toString());
            double b=Double.parseDouble(stack.pop().toString());
            if(p.get(i).equals("+"))
            {
                stack.push(b+a);
            }
            else if(p.get(i).equals("-"))
            {
                stack.push(b-a);
            }
            else if(p.get(i).equals("/"))
            {
                stack.push(b/a);
            }
            else if(p.get(i).equals("*"))
            {
                stack.push(b*a);
            }
        }
    }
    System.out.println(stack);
    return 0;
}

public static void main(String[] args) {
        // TODO code application logic here
        String s=new String("159*(79+23)-10/4+(22*54-67*(25*58))");
        Main.result(Main.toPostfix(s));
        System.out.println(159*(79+23)-10/4+(22*54-67*(25*58)));
    }
}

Could you please only include the *relevant* parts of the code? And perhaps describe it rather than just giving us the code? — CC Inc, Aug 17 '13 at 01:35

Arithmetic Expression Evaluation in j2me: Works only for single digit operands

1 Answers1