Finishing java code. Program should read from infix text file and convert the numbers from infix to postfix notation and then give its value. The program should read from the infix text file and output the results to another text file called csis.txt. This last part is where im having difficulty coding please help with updated and working java program. The infix.txt should have the following numbers to be converted and return its value.

8 + 4 * 2 - 6
7 * 2 - 4 * 3 + 2 * 5
2 * 3 * 4 - 8 + 9 / 3 / 3
5 + 7 * 4 - 6
4 * ( 3 + 2 * 4 ) - 7
( 5 + 7 ) / ( 9 - 5 )
3 * ( 5 * ( 5 - 2 ) ) - 9
( ( 5 * ( 4 + 2 ) - ( 8 + 8 ) / 2 ) - 9 ) ^ 3
( ( 5 + 5 * ( 6 - 2 ) + 4 ^ 2 ) * 8 )
( ( ( 3 ^ 4 ) ) )

The code i have is the folowing:

// Driver class

import java.io.*;
import java.util.*;

public class Driver {
public static void main(String[]args) throws IOException
{
Scanner fileScan = new Scanner(new File("infix.txt"));
InfixToPostfix infixToPostfix = new InfixToPostfix();
EvalPostfix evalPostfix = new EvalPostfix();

{
try {

File file = new File("infix.txt");

if (file.createNewFile()){
System.out.println("File is created!");
}else{
System.out.println("File already exists.");
}

} catch (IOException e) {
e.printStackTrace();
}

}

while(fileScan.hasNextLine())
{
String infix = fileScan.nextLine();
String postfix = infixToPostfix.convertToPostfix(infix);
String result = evalPostfix.evalPostfix(postfix);

System.out.println("Infix: "+ infix);
System.out.println("Postfix: "+ postfix);
System.out.println("Result: "+ result);
System.out.println();
}

}
}

// Object Stack

public class ObjectStack implements ObjectStackInterface {
private Object[] item;
private int top;
public ObjectStack()
{
item = new Object[1];
top = -1;
}
public boolean isEmpty()
{
return top == -1;
}
public boolean isFull()
{
return top == item.length -1;
}
public void clear()
{
item = new Object[1];
top = -1;
}
public void push(Object o)
{
if(isFull())
resize(2 * item.length);
item[++top] = o;
}
private void resize(int size)
{
Object[] temp = new Object[size];
for(int i = 0;i <=top;i++)
temp[i] = item[i];
item = temp;
}
public Object pop()
{
if(isEmpty())
{
System.out.println("Stack Underflow");
System.exit(1);
}
Object temp = item[top--];
if(top == item.length/4)
resize(item.length/2);
return temp;
}
public Object top()
{
if(isEmpty())
{
System.out.println("Stack Underflow");
System.exit(1);
}

return item[top];
}

}

// ObjectStack Interface

import java.io.File;
import java.io.IOException;

public interface ObjectStackInterface {
public boolean isEmpty();
public boolean isFull();
public void clear();
public void push(Object o);
public Object pop();
public Object top();
}

// EvalPostfix

public class EvalPostfix {
private ObjectStack objStack;
public EvalPostfix()
{
objStack = new ObjectStack();
}

public String evalPostfix(String postfix)
{
int op1 = 0, op2 = 0;
int result = 0;
String str = null;


String[] tokens = postfix.split(" ");
for(int i = 0; i < tokens.length; i++)
{
str = tokens[i];
if(!("+".equals(str) || "-".equals(str) || "*".equals(str) || "/".equals(str) || "^".equals(str)))
{
objStack.push(str);
}
else
{
op1 = Integer.valueOf((String) objStack.pop());
op2 = Integer.valueOf((String) objStack.pop());

switch(str)
{
case "+":
result = (op2 + op1);
break;
case "-":
result = (op2 - op1);
break;
case "*":
result = (op2 * op1);
break;
case "/":
result = (op2 / op1);
break;
case "^":
result = (int) Math.pow(op2, op1);
break;
}
objStack.push("" + result);
}
}

String val = (String) objStack.pop();
return val;
}

}

// Infix to Postfix

public class InfixToPostfix {
private ObjectStack objStack;

public InfixToPostfix()
{
objStack = new ObjectStack();
}

public String convertToPostfix(String infix)
{
String[] tokens = infix.split(" ");
String postfix = "";

for(int i = 0; i < tokens.length; i++)
{
char ch = tokens[i].charAt(0);

if(ch <= '9' && ch >= '0')
{
postfix += ch + " ";
}

else if(ch == '^' || ch == '/' || ch == '*' || ch == '+' || ch == '-' || ch == '(')
{
while(!objStack.isEmpty() && (getPriority(ch) <= getPriority((Character) objStack.top())) && (ch != '('))
{
postfix += objStack.pop() + " ";
}
objStack.push(ch);
}
else if(ch == ')')
{
while((!(objStack.top().equals('('))))
{
postfix += objStack.pop() + " ";
}
objStack.pop();
}
}

while(!objStack.isEmpty())
{
postfix += objStack.pop() + " ";
}

return postfix;
}

private int getPriority(char ch)
{
switch(ch)
{
case '^':
return 3;
case '/':
case '*':
return 2;
case '+':
case '-':
return 1;
default:
return 0;
}
}

}