jodd-htmlstapler/src/main/java/jodd/htmlstapler/HtmlStaplerBundlesManager.java
public void setRandomDigestChars(final int randomDigestChars) {
		this.randomDigestChars = randomDigestChars;

		if (randomDigestChars == 0) {
			uniqueDigestKey = null;
		}
		else {
			uniqueDigestKey = new RandomString().randomAlphaNumeric(randomDigestChars);
		}
	}
public void setRandomDigestChars(final int randomDigestChars) {
		this.randomDigestChars = randomDigestChars;

		if (randomDigestChars == 0) {
			uniqueDigestKey = null;
		}
		else {
			uniqueDigestKey = new RandomString().randomAlphaNumeric(randomDigestChars);
		}
	}
Sets the number of random characters that will be appended to the
{@link #createDigest(String) digest}. When it is set to 0, nothing
will be appended to the digest. Otherwise, a random string will be
generated (containing only letters and digits) and appended to the
digest.
<p>
Random digest chars is a <b>unique</b> key per one VM!
This key is initialized only once.
This is useful to automatically expire any cache that browsers may have in
JS and CSS files, so that changes in those files will be downloaded by the
browser.