Provides a definition of a macro language or syntax and parsing into objects in a program.
Given any string expression and a token, filter out the information you want. The below is a simple parser program. the myParser method can be used to parse any expression. The composite, visit and iterator patterns have been used.
import java.util.*;
class Parser{
private String expression;
private String token;
private List result;
private String interpreted;
public Parser(String e, String t) {
expression = e;
token = t;
}
public void myParser() {
StringTokenizer holder = new StringTokenizer(expression, token);
String[] toBeMatched = new String[holder.countTokens()];
int idx = 0;
while(holder.hasMoreTokens()) {
String item = holder.nextToken();
int start = item.indexOf(",");
if(start==0) {
item = item.substring(2);
}
toBeMatched[idx] = item;
idx ++;
}
result = Arrays.asList(toBeMatched);
}
public List getParseResult() {
return result;
}
public void interpret() {
StringBuffer buffer = new StringBuffer();
ListIterator list = result.listIterator();
while (list.hasNext()){
String token = (String)list.next();
if (token.equals("SFO")){
token = "San Francisco";
}else if(token.equals("CA")) {
token = "Canada";
}
//...
buffer.append(" " + token);
}
interpreted = buffer.toString();
}
public String getInterpretedResult() {
return interpreted;
}
public static void main(String[] args) {
String source = "dest='SFO',origin='CA',day='MON'";
String delimiter = "=,'";
Parser parser = new Parser(source, delimiter);
parser.myParser();
parser.interpret();
String result = parser.getInterpretedResult();
System.out.println(result);
}
}
java Parser
dest San Francisco origin Canada day MON