CheckBalanced.java

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

public class CheckBalanced {

    /**
    *   Program: CheckBalanced.java
    *   Purpose: Read a Java source code file and check it has balanced brackets{}.
    *   Creator: Chris Clarke, author "50 Java Program Source Codes" (in paperback and e-book)
    *        - and now also by Chris Clarke: "50 More Java Source Codes".
    *   Created: 31.10.2014
    */

    // create linked list object as instance variable
    LinkedList<Integer> list = new LinkedList<Integer>();

    // initialise top (of stack)
    static int top = -1;

    public void push(int t) {
        list.add(new Integer(++t));
    } // push()

    public int pop() {
        if (top != -1)
            return list.remove(top--);
        return top;
    } // pop()

    public static void main(String[] args) {
        if (args.length==0) {
            System.out.println("Usage: java CheckBalanced \"MyProgram.java\"");
            return;
        } // if

        File f;
        Scanner scan = null;
        String line;
        char ch;

        CheckBalanced stack = new CheckBalanced();

        try {
            f = new File(args[0]);
            scan = new Scanner(f);
        } catch (IOException e) {
            System.out.println("Caught IOException");
            return;
        } // try

        while (scan.hasNextLine()) {
            line = scan.nextLine();
            for (int i=0; i<line.length(); i++) {
                ch = line.charAt(i);
                if (ch=='{')
                    stack.push(top);

                if (ch=='}')
                    top = stack.pop();

            } // for
        } // while

        if (scan!=null) scan.close();

        if (top == -1)
            System.out.println("BALANCED");
        else
            System.out.println("NOT BALANCED");

    } // main()

} // class CheckBalanced