Cannot resolve method 'isBlank' in 'StringUtils'

The method `isBlank()` was introduced in Java 11 and is not available in earlier versions. If you are using an earlier version of Java, you will not be able to use this method directly.

One way to check if a string is blank in earlier versions of Java is to use the `trim()` method to remove leading and trailing whitespace and then check if the resulting string is empty:

String str = "   ";
if(str.trim().isEmpty()) {
    // String is blank
}

Alternatively, you can create your own utility method to check if a string is blank:

public static boolean isBlank(String str) {
    return str == null || str.trim().isEmpty();
}

Then you can use this method to check if a string is blank:

String str = "   ";
if(StringUtils.isBlank(str)) {
    // String is blank
}

Note that the `StringUtils` class you are referring to is likely from the Apache Commons Lang library, which provides additional utility methods for working with strings. If you are using this library, you can use the `StringUtils.isBlank()` method directly.