如何使用Lucene TestUtil随机生成Unicode字符串

我正在编写一些生成随机Unicode字符串的代码。我尝试使用Lucene Test Utils生成随机Unicode字符串,如下所示

    for (int i = 0; i < 5000; i++) {
        Random random = new Random();
        final String s = TestUtil.randomUnicodeString(random, 12);
        //final String s = TestUtil.randomUnicodeString(random);Tried both
        final byte[] utf8 = new byte[s.length() * UnicodeUtil.MAX_UTF8_BYTES_PER_CHAR];
        final int utf8Len = UnicodeUtil.UTF16toUTF8(s, 0, s.length(), utf8);
        if(utf8Len !=8)
        {
            System.out.println("$$$$");
        }
    }

所以我检查了lucene6.2.0版本的lucene代码中的destring实现

public static String randomUnicodeString(Random r, int maxLength) {
final int end = nextInt(r, 0, maxLength);
if (end == 0) {
  // allow 0 length
  return "";
}
final char[] buffer = new char[end];
randomFixedLengthUnicodeString(r, buffer, 0, buffer.length);
return new String(buffer, 0, end);

}

 public static void randomFixedLengthUnicodeString(Random random, char[] chars, int offset, int length) {
int i = offset;
final int end = offset + length;
while(i < end) {
  final int t = random.nextInt(5);
  if (0 == t && i < length - 1) {
    // Make a surrogate pair
    // High surrogate
    chars[i++] = (char) nextInt(random, 0xd800, 0xdbff);
    // Low surrogate
    chars[i++] = (char) nextInt(random, 0xdc00, 0xdfff);
  } else if (t <= 1) {
    chars[i++] = (char) random.nextInt(0x80);
  } else if (2 == t) {
    chars[i++] = (char) nextInt(random, 0x80, 0x7ff);
  } else if (3 == t) {
    chars[i++] = (char) nextInt(random, 0x800, 0xd7ff);
  } else if (4 == t) {
    chars[i++] = (char) nextInt(random, 0xe000, 0xffff);
  }
}

}

那么我得到这个例外的原因是什么呢

Exception in thread "main" java.lang.NoClassDefFoundError: com/carrotsearch/randomizedtesting/generators/RandomInts
at org.apache.lucene.util.TestUtil.nextInt(TestUtil.java:433)
at org.apache.lucene.util.TestUtil.randomUnicodeString(TestUtil.java:505)
at luceneLab.lab.main(lab.java:33)Caused by: java.lang.ClassNotFoundException: com.carrotsearch.randomizedtesting.generators.RandomInts
at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:335)
at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
... 3 more

提前谢谢。