Checking if a string contains a dot

You only need

s.contains (".");

contains() method of String class does not take regular expression as a parameter, it takes normal text.

String s = "test.test";

if(s.contains("."))
{
    System.out.println("string contains dot");
}

String#contains receives a plain CharacterSequence e.g. a String, not a regex. Remove the \\ from there.

String s = "test.test";
if (s.contains(".")) {
    System.out.println("string contains dot");
}

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