A quick java program to check proper matching of braces in a file.

CheckBraces.java

import java.io.*;

public class CheckBraces{
	// Print errors and set exit status
    public static void die(String msg){
        System.err.println(msg);
        System.exit(1);
    }

	// Process a file named with a CLI arg
    public static void main(String[] args){
		// Check inputs
        if (args.length < 1) CheckBraces.die("No file provided to check.");
        BufferedReader reader = null;
        try{ reader = new BufferedReader(new FileReader(args[0])); }
        catch(Exception e){ die("Could not open file '" + args[0] + "'."); }

		// Set up variables
        String braces = "{}[]()";
        int len = 0;
        int index = -1;
        int lastIndex = -1;
        int stackEnd = 0;
        int MAX_READ = 1024;
        int MAX_STACK = 128;
        char[] buf = new char[MAX_READ];
        char[] stack = new char[MAX_STACK];

		// Read input from file
        while(true){
            try { len = reader.read(buf, 0, MAX_READ); }
            catch(Exception e){ die("Error reading file '" + args[0] + "'."); }
            if (len < 1) break;

			// Check read characters for braces
			for(int i=0; i<len; ++i){
                int temp = braces.indexOf(buf[i]);
                if(temp == -1) continue;
				index = temp;

				// Open braces
				if(index%2 == 0){
					stack[stackEnd++] = buf[i];
					lastIndex = index;

				// Close braces
				}else{
					if(stackEnd <= 0) die("Found close '" + buf[i] + "' with no open '" + braces.charAt(index - 1) + "'.");
					if(index-lastIndex != 1) die("Found '" + buf[i] + "' when expecting '" + braces.charAt(lastIndex + 1) + "'.");

					if(--stackEnd == 0){
						lastIndex = -1;
					}else{
						lastIndex = braces.indexOf(stack[stackEnd-1]);
					}
				}
            }
        }

		// Final check
        if (stackEnd > 0) die("End of file while still expecting '" + braces.charAt(lastIndex + 1) + "'.");
    }
}