add comment and test

hutool-core/src/test/java/cn/hutool/core/lang/UUIDTest.java

@@ -0,0 +1,21 @@
+package cn.hutool.core.lang;
+
+import cn.hutool.core.collection.ConcurrentHashSet;
+import cn.hutool.core.thread.ThreadUtil;
+import org.junit.Assert;
+import org.junit.Test;
+
+import java.util.Set;
+
+public class UUIDTest {
+
+	/**
+	 * 测试UUID是否存在重复问题
+	 */
+	@Test
+	public void fastUUIDTest(){
+		Set<String> set = new ConcurrentHashSet<>(100);
+		ThreadUtil.concurrencyTest(100, ()-> set.add(UUID.fastUUID().toString()));
+		Assert.assertEquals(100, set.size());
+	}
+}

hutool-core/src/test/java/cn/hutool/core/util/TypeUtilTest.java

@@ -56,4 +56,5 @@ public class TypeUtilTest {
 		public void service(String string) {
 		}
 	}
+
 }