jodd-core/src/main/java/jodd/util/StringUtil.java
public static String findCommonPrefix(final String... strings) {
		StringBuilder prefix = new StringBuilder();
		int index = 0;
		char c = 0;

		loop:
		while (true) {
			for (int i = 0; i < strings.length; i++) {

				String s = strings[i];
				if (index == s.length()) {
					break loop;
				}

				if (i == 0) {
					c = s.charAt(index);
				} else {
					if (s.charAt(index) != c) {
						break loop;
					}
				}
			}

			index++;
			prefix.append(c);
		}
		return prefix.length() == 0 ? StringPool.EMPTY : prefix.toString();
	}
public static String findCommonPrefix(final String... strings) {
		StringBuilder prefix = new StringBuilder();
		int index = 0;
		char c = 0;

		loop:
		while (true) {
			for (int i = 0; i < strings.length; i++) {

				String s = strings[i];
				if (index == s.length()) {
					break loop;
				}

				if (i == 0) {
					c = s.charAt(index);
				} else {
					if (s.charAt(index) != c) {
						break loop;
					}
				}
			}

			index++;
			prefix.append(c);
		}
		return prefix.length() == 0 ? StringPool.EMPTY : prefix.toString();
	}
Finds common prefix for several strings. Returns an empty string if
arguments do not have a common prefix.