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Java regular expression to check if the first and last character of a string are same

January 15, 2022

I’m trying to to check if the first and last characters of a string are the same. The very basic approach is to simply compare the first and last characters and it’s done.

str.charAt(0) == str.charAt(str.length()-1)?true:false;

str = "ababa"; //shall return true.

str = "abab"; //shall return false.

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But is there a way to compare the whole string using pattern matcher with a pre defined regex expression?

>Solution :

Using String#matches with a backreference:

List<String> inputs = Arrays.asList(new String[] { "ababa", "abab" });
for (String input : inputs) {
    if (input.matches("(.).*\\1")) {
        System.out.println("MATCH:    " + input);
    }
    else {
        System.out.println("NO MATCH: " + input);
    }
}

This prints: