Assembler for Hack Assembly Language

I have been reading this great book and I decided to do the Project in Chapter 5: Writing an Assembler for the Hack Assembly Language.

You can find the specification for the Hack Machine Language and the Hack Assembly Language here.

Here is my implementation:

`package biz.tugay.hack.assembler;
/ User: koray.asm@tugay.biz Date: 07/03/15 Time: 10:47 /

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

public class HackAssembler {

private static File machineLanguageFile;
private static File assembled;
private static FileWriter fileWriter;
private static int variableAddressCounter = 16;
private static Map variableAddressMap = new HashMap();
private static Map loopAddressMap = new HashMap();

public static void main(String[] args) throws IOException {
doChecksForSourceFile(args);
checkLabelsAndPopulateLoopAddressMap(machineLanguageFile);
Scanner machineLanguageFileScanner = new Scanner(machineLanguageFile);
fileWriter = new FileWriter(assembled);
while(machineLanguageFileScanner.hasNextLine()){
String nextAssemblyLine = machineLanguageFileScanner.nextLine();
assemble(nextAssemblyLine);
}
fileWriter.flush();
fileWriter.close();
}

private static void assemble(String lineToBeAssembled) throws IOException {
if(lineToBeAssembled.startsWith("(")) {

}
else if(lineToBeAssembled.startsWith("@")) {
assemble_A_Instruction(lineToBeAssembled);
fileWriter.write(System.lineSeparator());
}
else {
assemble_C_Instruction(lineToBeAssembled);
fileWriter.write(System.lineSeparator());
}
}

private static void assemble_C_Instruction(String lineToBeAssembled) throws IOException {
String compMnemonnic;
String destinationMnemonnic = "null";
String jumpMnemonnic = "null";

String compBinaryR

My two cents:

-
Your lines are long:


"code gets harder to read the wider it becomes"

• You pass around ambiguously named variables. At first glance, it's hard to know what args[0] or subString is.

• Some names are very long.

-
Spaces.

for(int i=0;i<zerosToAppend;i++);

can easily be

for(int i = 0; i < zerosToAppend; i++);

-
There are no comments describing what the code does.


"Comments can never be replaced by code alone."

-
Strings are hard-coded all over the place. It's much easier to understand

assembled = new File(fileName + FILE_SUFFIX);

than

assembled = new File(args[0]+".hack");

It helps to have these type of things all in one place in anticipation of one of them needing change.

Over all, it looks pretty decent. Just remember: K.I.S.S.

StackExchange Code Review Q#83495, answer score: 7