Switch or if statements in writing an interpreter in java

Question

Current assignment needs me to write a program to read a file with instructions in a very tiny and basic programming language (behaves a little like FORTRAN) and execute those i

Answer 1

If you are talking about converting strings to integers then you could do it with an Java enumerated type:

private enum ReservedWord {
   LET,
   ...
}

// skip blank lines and comments
String[] tokens = codeLine.split(" ");
ReservedWord keyword;
try {
   keyword = ReservedWord.valueOf(tokens[0]);
} catch (IllegalArgumentException e) {
   // spit out nice syntax error message
}

You could also put the processing of the line inside of the enum as a method if you'd like. You could also do it with a Map:

private final Map reservedWords = new HashMap();
private final int RESERVED_WORD_LET 1
...
{
   reservedWords.put("LET", RESERVED_WORD_LET);
   ...
}

// skip blank lines and comments
String[] tokens = codeLine.split(" ");
Integer value = reservedWords.get(tokens[0]);
if (value == null) // handle error... ;
switch (value) {
   case 1:
       // LET
       ...
}