Interpreter.java

import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.Reader;
import java.io.FileNotFoundException;
import java.nio.charset.Charset;
import java.util.List;
import java.util.LinkedList;

public class Interpreter
{
    public static void main(String args[])
    {                
        boolean debug = false;
        
        if (args.length < 1) { Util.Writeln("Usage: Demo <script>"); return; }
        if (args.length > 1) { if (args[1].equals("debug")) debug = true; }        
        
        Interpreter interpreter = new Interpreter();
            
        String sourceCode = interpreter.ReadFile(args[0]);
        interpreter.Interpret(sourceCode, debug);
    }

    public void Interpret(String source, boolean debug)
    {        
        Tokenizer tokenizer = new Tokenizer();
        Parser parser = new Parser(tokenizer.Tokenize(source));
        
        if (debug) DumpTokens(parser);
        
        Node program = parser.Program();
        program.eval();
    }

    public void DumpTokens(Parser parser)
    {
        for (Token token: parser.getTokens())
            Util.Writeln("Type: " + token.type + " Text: " + token.text+" ");
        Util.Writeln();    
    }
        
    private String ReadFile(String path)
    {
        FileInputStream stream = null;
        InputStreamReader input = null;
        try
        {
            stream = new FileInputStream(path);                       
            input = new InputStreamReader(stream, Charset.defaultCharset());
                
            Reader reader = new BufferedReader(input);
            StringBuilder builder = new StringBuilder();
            char[] buffer = new char[8192];
            int read;
            while ((read = reader.read(buffer, 0, buffer.length)) > 0)
            {
                builder.append(buffer, 0, read);
            }
            //Keep the space in the end
            builder.append(" ");
            return builder.toString();
        }
        catch (FileNotFoundException e)
        {
            String errMsg = "FILE NOT FOUND. ";
            String sourceInfo = "Error in Interpreter.java->" 
                                + "ReadFile(String path) method. ";
            Util.Writeln(sourceInfo + errMsg);
            System.exit(0);
        }
        catch (IOException e)
        {
            String errMsg = "Error while reading the script. ";
            String sourceInfo = "Error in Interpreter.java->" 
                                + "ReadFile(String path) method. ";
            Util.Writeln(sourceInfo + errMsg);
            System.exit(0);
        }
        catch (Exception e)
        {
            String errMsg = "Error while reading the script. ";
            String sourceInfo = "Error in Interpreter.java->" 
                                + "ReadFile(String path) method. ";
            Util.Writeln(sourceInfo + errMsg + e);
            System.exit(0);
        }        
        finally
        {
            try
            {
                input.close();
                stream.close();
            }
            catch (Exception e)
            {
                String errMsg = "Error while closing a stream or a stream reader. ";
                String sourceInfo = "Error in Interpreter.java->" 
                                    + "ReadFile(String path) method. ";                
                Util.Writeln(sourceInfo + errMsg + e);
                System.exit(0);
            }            
        }
                
        return null;
    }    
}