stacks - verify well-formed equations, InFix to PostFix

Hi...
I'm a new user here. I've stumbled across this place on a couple occasions in the past, and it worked out to my advantage when I needed a little help with some coding assignments.
My Data Structures class is working on stacks right now, and that is our current assignment.

This assignment is 3 parts, 1 of which is optional for extra credit.
The 2 parts I am working on, before hopefully also doing the third for extra points, are as follows:

1) verify whether or not equations are balanced, according to parentheses, brackets, and curly braces.

2) InFix to PostFix conversions.
example: (a+b)*c => ab+c*

All of the parts need to evaluate from a .txt file that is read in.
Here is what I have thrown together so far:

class stackOb {
	int top;
	char stack[];
	int maxLen;
	
	public stackOb(int maxLen) {
		stack = new char[maxLen];
		top = -1;
		this.maxLen = maxLen;
	}
	
	public void push(char item) {
		
	}
	
	public char pop() {
	}
	
	public boolean empty() {
		if (top == -1) {
			return true;
		}
		else {
			return false;
		}
	}
	
	public void reset() {
		top = -1;
	}
	
	public void showStack() {
		int j;
		System.out.println(" ");
		System.out.println("Stack contents ...");
		for(j=top;j>-1;j--) {
			System.out.println(stack[j]);
		}
		System.out.println(" ");
	}
	
	public void showStack0toTop() {
		int j;
		System.out.println(" ");
		System.out.println("Stack contents ...");
		for(j=0;j<=top;j++) {
			System.out.print(stack[j]);
		}
		System.out.println(" ");
	}

}

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

public class fileIn {
	String fname;

    public fileIn() {
    	System.out.println("starting fileIn()...");
    	getFileName();
    	readFileContents();
    }
    
	 public void getFileName() {
    	Scanner in = new Scanner(System.in);
    	System.out.println("Enter file name please.");
    	fname = in.nextLine();
    	System.out.println("You entered "+fname);
    }
	 
    public void readFileContents() {
    	boolean looping;
    	DataInputStream in;
    	String line;
    	int j, len;
    	char ch;
    	
    	try {
            in = new DataInputStream(new FileInputStream(fname));
            looping = true;
            while(looping) {
				
                if (null == (line = in.readLine())) {
                    looping = false;
                    in.close();
                }
                else {
						System.out.println("line = "+line);
                	len = line.length();
                	for(j=0;j<len;j++){
                		System.out.println("line["+j+"] = "+line.charAt(j));
                	}
					 }
            } 
                	
        } 
        
        catch(IOException e) {
            System.out.println("Error " + e);
        } 
    }
    
    public static void main(String[] args) {
		System.out.println("START main method...");
		fileIn f = new fileIn();
		System.out.println("END main method...");
	}
	
}

This code I've provided will read in the .txt file and analyze each line at a character level, which I'm sure I need to do for this assignment. I've also included the structure for my stack class.

I've been staring at it for a while now, and I'm a little stumped with where to go from here. Perhaps I need to go back and reread some of the material on stacks and stack operations in order to get a clearer picture of what exactly I need to do.

Any tips or pointers of which direction to go from here would be greatly appreciated! :cool:

nola_Coder

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49 posts since Oct 2009

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stacks - verify well-formed equations, InFix to PostFix

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