Replace StringUtils.containsOnly with Regex

public class TempTest {
    Pattern r = Pattern.compile("^[a-zA-Z0-9_]*$");
    @Test
    public void test() {
        final char[] VALID_MODELNAME = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890_".toCharArray();
        String s1 = "abc@";
        System.out.println("Call StringUtils.containsOnly 100 times");
        long start = System.nanoTime();
        for(int i =0; i<100; ++i) {
            StringUtils.containsOnly(s1, VALID_MODELNAME);
        }
        long end = System.nanoTime();
        System.out.println(end - start);

        System.out.println("Call Regex match 100 times");
        start = System.nanoTime();
        for(int i =0; i<100; ++i) {
            containsByRegex(s1);
        }
        end = System.nanoTime();
        System.out.println(end - start);

    }

    private boolean containsByRegex(final String s) {
        Matcher matcher = r.matcher(s);
        return matcher.find();
    }
}

Call StringUtils.containsOnly 100 times
4740997
Call Regex match 100 times
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