See if String Contains An Element in an Array

Question

I am trying to go through an array of Operators to see if one of the operators is located in the String.

For example:

String[] OPERATORS    = { "<", "<=", ... };
String line = "a <= b < c ";

How would I go about going through a loop that checks to see if an operator is in the string?

Also, say my method found that "<" is located in the string at "<= "

However, I am looking for the actual string " <= ". How would I go about accounting for that?

Answer 1

I would use a regex instead of having array of all the operators. Also, make sure the operators are in the exact order in your regex, i.e., <= should be before <, similarly, == should be before =:

String regex = "<=|<|>=|>|==|=|\\+|-";

String line = "a <= b < c ";

Matcher matcher = Pattern.compile(regex).matcher(line);

while (matcher.find()) {
    System.out.println(matcher.start() + " : " + matcher.group());
} 

Output:

2 : <=
7 : <

The trick is that, before the regex matches <, of <=, it will already be matched by <=, as it comes before <.