stringAlgorithms/Algorithms.java

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package stringAlgorithms;

public class Algorithms {

    private Algorithms() {
    }

    public static String reverse(String str) {
        String newString = null;
        if (str != null) {
            char buf[] = str.toCharArray();
            int l = 0;
            int r = buf.length - 1;
            while (l < r) {
                char t = buf[l];
                buf[l] = buf[r];
                buf[r] = t;
                l++;
                r--;
            }
            newString = new String(buf);
        }
        return newString;
    } // reverse

    public static boolean isSubstring(String sub, String str) {
        boolean match = false;
        if (sub != null && str != null) {
            int subLen = sub.length();
            int strLen = str.length();
            if (subLen <= strLen) {
                int delta = strLen - subLen;
                int i = 0;
                do {
                    match = true;
                    int j = i;
                    for (int ix = 0; ix < subLen; ix++) {
                        if (sub.charAt(ix) != str.charAt(j)) {
                            match = false;
                            break;
                        }
                        j++;
                    } // for j
                    i++;
                } while (i <= delta && (!match));
            }
        }
        return match;
    } // isSubstring

}