Find longest non repeating sub string from String.

package practice.sample;

public class LogestNonRepeatingString {

private StringBuilder findLongestSubString(String arsStr) {

StringBuilder stCurr = new StringBuilder();

StringBuilder strPremax = null;

int curLength = 0;

int maxLength = 0;

for (int i = 0; i < arsStr.length(); i++) {

char c = Character.toLowerCase(arsStr.charAt(i));

int prevIndex = contains(c, stCurr);

if (prevIndex == -1) {

stCurr.append(c);

curLength++;

if (maxLength < curLength) {

maxLength = curLength;

}

} else {

if (strPremax == null || (strPremax.length() < stCurr.length())) {

strPremax = stCurr;

}

stCurr = new StringBuilder(stCurr.substring(prevIndex + 1))

.append(c);

}

}

return stCurr.length() > strPremax.length() ? stCurr : strPremax;

}

private int contains(char charAt, StringBuilder st) {

for (char c : st.toString().toCharArray()) {

if (c == charAt) {

return st.toString().indexOf(c);

}

}

return -1;

}

public static void main(String args[]) {

LogestNonRepeatingString l = new LogestNonRepeatingString();

StringBuilder str = l.findLongestSubString("XYZARPUA");

System.out.println(str);

}

}