Java Splitting Strings with several conditions

Question

I want to split a string along several different conditions - I understand there is a Java String method called String.split(element), which splits the String into an array based on the element specified.

However, splitting among more objects seems to be very complex -- especially if the split must occur to a range of elements.

Precisely, I want java to split the string

• "a>=b" into {"a",">=","b"}

• "a>b" into {"a", ">", "b"}

• "a==b" into {"a","==","b"}

I have been fiddling around with regex too just to see how to split it exactly based on this parameters, but the closest I've gotten is just splitting along a single character.

EDIT: a and b are arbitrary Strings that can be of any length. I simply want to split along the different kinds of comparators ">",">=","==";

For example, a could be "Apple" and b could be "Orange".

So in the end I want the String from "Apple>=Orange" into {"Apple", ">=", "Orange"}

Answer 1

You can use regular expressions. No matter if you use a, or b or abc for your variables you'll get the first variable in the group 1, the condition in the group 2 and the second variable in the group 3.

    Pattern pattern = Pattern.compile("(\\w+)([<=>]+)(\\w+)");
    Matcher matcher = pattern.matcher("var1>=ar2b");

    if(matcher.find()){
        System.out.println(matcher.group(1));
        System.out.println(matcher.group(2));
        System.out.println(matcher.group(3));
    }

Answer 2

The following code works for your examples:

System.out.println(Arrays.asList("a<=b".split("\\b")));

It splits the string on word boundaries.

If you need more elaborate splitting, you have to provide more examples.

Answer 3

You could code it out by hand and use whichever tokens you want to split on like so

public String[] splitString(String word)
{
    String[] pieces;
    String[] tokens = {"==", ">=", "<=","<", ">"};
    for(int i = 0; i < tokens.length; i++)
    {
        if(a.contains(tokens[i]))
        {
            pieces = {
                    word.substring(0, word.indexOf(tokens[i])), 
                    tokens[i], 
                    word.substring(word.indexOf(tokens[i]) + tokens[i].length(), word.length())};
            return pieces;
        }
    }
    return pieces;
}

This will return an array with whatever is before the token found, the token itself and whatever is left.