Exercise10_25.java

package ch_10;

import java.util.ArrayList;
import java.util.Arrays;

/**
 * **10.25 (New string split method) The split method in the String class returns an
 * array of strings consisting of the substrings split by the delimiters. However, the
 * delimiters are not returned. Implement the following new method that returns
 * an array of strings consisting of the substrings split by the matching delimiters,
 * including the matching delimiters.
 * <p>
 * public static String[] split(String s, String regex)
 * For example, split("ab#12#453", "#") returns ab, #, 12, #, 453 in an
 * array of String, and split("a?b?gf#e", "[?#]") returns a, b, ?, b, gf,
 * #, and e in an array of String.
 */
public class Exercise10_25 {

    public static void main(String[] args) {
        /* Tests */
        String s = "ab#12#453";
        String regex = "#";
        String s2 = "a?b?gf#e";
        String regex2 = "[?#]";

        System.out.println("split(\"ab#12#453\",\"#\"): " + Arrays.toString(split(s, regex)));
        System.out.println("split(\"a?b?gf#e\",\"[?#]\"): " + Arrays.toString(split(s2, regex2)));
    }

    public static String[] split(String s, String regex) {
        ArrayList<String> splitList = new ArrayList<>();
        if (regex == null || regex.length() < 1) {
            return new String[]{"regex must not be null and length must be greater than 0"};
        }

        ArrayList<Character> splitters = new ArrayList<>();
        for (char ch : regex.toCharArray()) {
            if (ch == '[' || ch == ']') continue;
            splitters.add(ch);
        }
        String subString = "";
        for (int i = 0; i < s.length(); i++) {
            if (splitters.contains(s.charAt(i))) {
                if (subString.length() > 0) {
                    splitList.add(subString);
                    subString = "";
                }

                splitList.add(s.charAt(i) + "");
                i++;
                while (i < s.length()) {
                    if (!splitters.contains(s.charAt(i))) {
                        subString = subString.concat(s.charAt(i) + "");
                    } else {
                        splitList.add(subString);
                        subString = "";
                        splitList.add(s.charAt(i) + "");
                        break;
                    }
                    i++;
                }
            } else {
                subString = subString.concat(s.charAt(i) + "");
            }
        }
        if (subString.length() > 0) {
            splitList.add(subString);
        }
        return splitList.toArray(new String[]{});

    }
}