diff --git a/README.md b/README.md
index d9f51d3..1c7bd26 100644
--- a/README.md
+++ b/README.md
@@ -1,23 +1,24 @@
 
 # ULID Creator
 
-A Java library for generating and handling ULIDs - _Universally Unique Lexicographically Sortable Identifiers_.
+A Java library for generating ULIDs.
 
 How to Use
 ------------------------------------------------------
 
-Create a ULID:
+Create a ULID as GUID:
 
 ```java
-String ulid = UlidCreator.getUlid();
+UUID ulid = UlidCreator.getUlid();
 ```
 
-Create a ULID as GUID object:
+Create a ULID string:
 
 ```java
-UUID ulid = UlidCreator.getGuid();
+String ulid = UlidCreator.getUlidString();
 ```
 
+
 ### Maven dependency
 
 Add these lines to your `pom.xml`.
@@ -27,7 +28,7 @@ Add these lines to your `pom.xml`.
 <dependency>
   <groupId>com.github.f4b6a3</groupId>
   <artifactId>ulid-creator</artifactId>
-  <version>1.0.2</version>
+  <version>1.1.0</version>
 </dependency>
 ```
 See more options in [maven.org](https://search.maven.org/artifact/com.github.f4b6a3/ulid-creator) and [mvnrepository.com](https://mvnrepository.com/artifact/com.github.f4b6a3/ulid-creator).
@@ -35,15 +36,15 @@ See more options in [maven.org](https://search.maven.org/artifact/com.github.f4b
 Implementation
 ------------------------------------------------------
 
-### ULID
+### ULID string
 
-The ULID is a unique and sortable 26 char sequence. See the [ULID specification](https://github.com/ulid/spec) for more information.
+The ULID is a 26 char sequence. See the [ULID specification](https://github.com/ulid/spec) for more information.
 
 See the section on GUIDs to know how the 128 bits are generated in this library.
 
 ```java
 // ULIDs
-String ulid = UlidCreator.getUlid();
+String ulid = UlidCreator.getUlidString();
 ```
 
 Examples of ULIDs:
@@ -71,17 +72,17 @@ Examples of ULIDs:
    milli     randomness
 ```
 
-### GUID
+### Ulid-based GUID
 
 The GUIDs in this library are based on the [ULID specification](https://github.com/ulid/spec). The first 48 bits represent the count of milliseconds since Unix Epoch, 1 January 1970. The remaining 60 bits are generated by a secure random number generator.
 
 Every time the timestamp changes the random part is reset to a new random value. If the current timestamp is equal to the previous one, the random bits are incremented by 1.
 
-The default random number generator is `SecureRandom`, but it's possible to use any RNG that extends `Random`.
+The default random number generator is `java.security.SecureRandom`, but it's possible to use any RNG that extends `java.util.Random`.
 
 ```java
 // GUID based on ULID spec
-UUID guid = UlidCreator.getGuid();
+UUID ulid = UlidCreator.getUlid();
 ```
 
 Examples of GUIDs based on ULID spec:
@@ -109,38 +110,28 @@ Examples of GUIDs based on ULID spec:
   millisecs        randomness
 ```
 
-#### How use the `GuidCreator` directly
+#### How use the `UlidBasedGuidCreator` directly
 
-These are some examples of using the `GuidCreator` to create ULIDs:
+These are some examples of using the `UlidBasedGuidCreator` to create ULIDs strings:
 
 ```java
-
-// with fixed timestamp strategy (for test cases)
-String ulid = UlidCreator.getGuidCreator()
-	.withTimestampStrategy(new FixedTimestampStretegy())
-	.createUlid();
 	
 // with your custom timestamp strategy
-String ulid = UlidCreator.getGuidCreator()
-	.withTimestampStrategy(new MyCustomTimestampStrategy())
-	.createUlid();
+TimestampStrategy customStrategy = new CustomTimestampStrategy();
+String ulid = UlidCreator.getUlidBasedGuidCreator()
+	.withTimestampStrategy(customStrategy)
+	.createString();
 
-// with your custom random number generator
-String ulid = UlidCreator.getGuidCreator()
-    .withRandomGenerator(new MyCustomRandom())
-    .createUlid();
-
-// with fast random generator (Xorshift128Plus with salt)
-int salt = (int) FingerprintUtil.getFingerprint();
-Random random = new Xorshift128PlusRandom(salt);
-String ulid = UlidCreator.getGuidCreator()
+// with `java.util.Random` number generator
+Random random = new Random();
+String ulid = UlidCreator.getUlidBasedGuidCreator()
     .withRandomGenerator(random)
-    .createUlid();
+    .createString();
     
 // with fast random generator (the same as above)
-String ulid = UlidCreator.getGuidCreator()
+String ulid = UlidCreator.getUlidBasedGuidCreator()
     .withFastRandomGenerator()
-    .createUlid();
+    .createString();
 
 ```
 
diff --git a/src/main/java/com/github/f4b6a3/ulid/UlidCreator.java b/src/main/java/com/github/f4b6a3/ulid/UlidCreator.java
index 7e08321..2f4934a 100644
--- a/src/main/java/com/github/f4b6a3/ulid/UlidCreator.java
+++ b/src/main/java/com/github/f4b6a3/ulid/UlidCreator.java
@@ -26,8 +26,8 @@ package com.github.f4b6a3.ulid;
 
 import java.util.UUID;
 
+import com.github.f4b6a3.commons.random.Xorshift128PlusRandom;
 import com.github.f4b6a3.ulid.creator.UlidBasedGuidCreator;
-import com.github.f4b6a3.ulid.exception.UlidCreatorException;
 
 /**
  * A factory for Universally Unique Lexicographically Sortable Identifiers.
@@ -40,61 +40,71 @@ public class UlidCreator {
 	}
 
 	/**
-	 * Returns ULID as GUID object.
+	 * Returns a ULID as GUID.
 	 * 
-	 * @return a GUID
+	 * The random component is generated by a secure random number generator:
+	 * {@link java.security.SecureRandom}.
+	 * 
+	 * @return a UUID
 	 */
 	public static UUID getUlid() {
-		return GuidCreatorLazyHolder.INSTANCE.create();
+		return UlidBasedGuidCreatorHolder.INSTANCE.create();
 	}
 
 	/**
-	 * Returns fast ULID as GUID object.
+	 * Returns a ULID string.
 	 * 
-	 * @return a GUID
-	 */
-	public static UUID getFastUlid() {
-		return FastGuidCreatorLazyHolder.INSTANCE.create();
-	}
-
-	/**
-	 * Returns a ULID.
+	 * The returning string is encoded to Crockford's base32.
+	 * 
+	 * The random component is generated by a secure random number generator:
+	 * {@link java.security.SecureRandom}.
 	 * 
 	 * @return a ULID
 	 */
 	public static String getUlidString() {
-		return GuidCreatorLazyHolder.INSTANCE.createString();
+		return UlidBasedGuidCreatorHolder.INSTANCE.createString();
 	}
 
 	/**
-	 * Returns a fast ULID.
+	 * Returns a ULID as GUID.
+	 * 
+	 * The random component is generated by a fast random number generator:
+	 * {@link Xorshift128PlusRandom}.
+	 * 
+	 * @return a UUID
+	 */
+	public static UUID getFastUlid() {
+		return FastUlidBasedGuidCreatorHolder.INSTANCE.create();
+	}
+
+	/**
+	 * Returns a fast ULID string.
+	 * 
+	 * The returning string is encoded to Crockford's base32.
+	 * 
+	 * The random component is generated by a fast random number generator:
+	 * {@link Xorshift128PlusRandom}.
 	 * 
 	 * @return a ULID
 	 */
 	public static String getFastUlidString() {
-		return FastGuidCreatorLazyHolder.INSTANCE.createString();
+		return FastUlidBasedGuidCreatorHolder.INSTANCE.createString();
 	}
 
 	/**
 	 * Return a GUID creator for direct use.
 	 * 
-	 * This library uses the {@link UlidBasedGuidCreator} internally to generate
-	 * ULIDs.
-	 * 
-	 * The {@link UlidBasedGuidCreator} throws a {@link UlidCreatorException} when
-	 * too many values are requested in the same millisecond.
-	 * 
 	 * @return a {@link UlidBasedGuidCreator}
 	 */
 	public static UlidBasedGuidCreator getUlidBasedCreator() {
 		return new UlidBasedGuidCreator();
 	}
 
-	private static class GuidCreatorLazyHolder {
+	private static class UlidBasedGuidCreatorHolder {
 		static final UlidBasedGuidCreator INSTANCE = getUlidBasedCreator();
 	}
 
-	private static class FastGuidCreatorLazyHolder {
+	private static class FastUlidBasedGuidCreatorHolder {
 		static final UlidBasedGuidCreator INSTANCE = getUlidBasedCreator().withFastRandomGenerator();
 	}
 }
diff --git a/src/main/java/com/github/f4b6a3/ulid/creator/UlidBasedGuidCreator.java b/src/main/java/com/github/f4b6a3/ulid/creator/UlidBasedGuidCreator.java
index febe3e1..5a001dd 100644
--- a/src/main/java/com/github/f4b6a3/ulid/creator/UlidBasedGuidCreator.java
+++ b/src/main/java/com/github/f4b6a3/ulid/creator/UlidBasedGuidCreator.java
@@ -27,13 +27,13 @@ package com.github.f4b6a3.ulid.creator;
 import java.util.Random;
 import java.util.UUID;
 
-import com.github.f4b6a3.ulid.timestamp.TimestampStrategy;
-import com.github.f4b6a3.ulid.util.UlidUtil;
+import com.github.f4b6a3.ulid.util.UlidConverter;
 import com.github.f4b6a3.commons.random.Xorshift128PlusRandom;
 import com.github.f4b6a3.commons.util.FingerprintUtil;
 import com.github.f4b6a3.commons.util.RandomUtil;
 import com.github.f4b6a3.ulid.exception.UlidCreatorException;
-import com.github.f4b6a3.ulid.timestamp.DefaultTimestampStrategy;
+import com.github.f4b6a3.ulid.strategy.TimestampStrategy;
+import com.github.f4b6a3.ulid.strategy.timestamp.DefaultTimestampStrategy;
 
 /**
  * Factory that creates lexicographically sortable GUIDs, based on the ULID
@@ -69,7 +69,7 @@ public class UlidBasedGuidCreator {
 	 * 
 	 * Return a GUID based on the ULID specification.
 	 * 
-	 * It has two parts:
+	 * A ULID has two parts:
 	 * 
 	 * 1. A part of 48 bits that represent the amount of milliseconds since Unix
 	 * Epoch, 1 January 1970.
@@ -85,6 +85,9 @@ public class UlidBasedGuidCreator {
 	 * 
 	 * The maximum GUIDs that can be generated per millisecond is 2^80.
 	 * 
+	 * The random part is generated by a secure random number generator:
+	 * {@link java.security.SecureRandom}.
+	 * 
 	 * ### Specification of Universally Unique Lexicographically Sortable ID
 	 * 
 	 * #### Components
@@ -116,7 +119,7 @@ public class UlidBasedGuidCreator {
 	 * 2^80 ULIDs within the same millisecond, or cause the random component to
 	 * overflow with less, the generation will fail.
 	 * 
-	 * @return {@link UUID} a UUID value
+	 * @return {@link UUID} a GUID value
 	 * 
 	 * @throws UlidCreatorException an overrun exception if too many requests are
 	 *                              made within the same millisecond.
@@ -135,13 +138,14 @@ public class UlidBasedGuidCreator {
 	}
 
 	/**
-	 * Return a ULID.
+	 * Returns a ULID string.
+	 * 
+	 * The returning string is encoded to Crockford's base32.
 	 * 
 	 * @return a ULID string
 	 */
 	public synchronized String createString() {
-		UUID guid = create();
-		return UlidUtil.fromUuidToUlid(guid);
+		return UlidConverter.toString(create());
 	}
 
 	/**
@@ -185,7 +189,8 @@ public class UlidBasedGuidCreator {
 	/**
 	 * Increment the random part of the GUID.
 	 * 
-	 * An exception is thrown when more than 2^80 increment operations are made.
+	 * An exception is thrown when more than 2^80 increment operations are made,
+	 * although it's extremely unlikely to occur.
 	 * 
 	 * @throws UlidCreatorException if an overrun happens.
 	 */
diff --git a/src/main/java/com/github/f4b6a3/ulid/exception/InvalidUlidException.java b/src/main/java/com/github/f4b6a3/ulid/exception/InvalidUlidException.java
new file mode 100644
index 0000000..7ff70a2
--- /dev/null
+++ b/src/main/java/com/github/f4b6a3/ulid/exception/InvalidUlidException.java
@@ -0,0 +1,34 @@
+/*
+ * MIT License
+ * 
+ * Copyright (c) 2020 Fabio Lima
+ * 
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ * 
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ * 
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package com.github.f4b6a3.ulid.exception;
+
+public class InvalidUlidException extends RuntimeException {
+
+	private static final long serialVersionUID = 1L;
+
+	public InvalidUlidException(String message) {
+		super(message);
+	}
+}
diff --git a/src/main/java/com/github/f4b6a3/ulid/exception/UlidCreatorException.java b/src/main/java/com/github/f4b6a3/ulid/exception/UlidCreatorException.java
index 8740403..e6f2078 100644
--- a/src/main/java/com/github/f4b6a3/ulid/exception/UlidCreatorException.java
+++ b/src/main/java/com/github/f4b6a3/ulid/exception/UlidCreatorException.java
@@ -26,8 +26,8 @@ package com.github.f4b6a3.ulid.exception;
 
 public class UlidCreatorException extends RuntimeException {
 
-	private static final long serialVersionUID = 6755381080404981234L;
-	
+	private static final long serialVersionUID = 1L;
+
 	public UlidCreatorException(String message) {
 		super(message);
 	}
diff --git a/src/main/java/com/github/f4b6a3/ulid/timestamp/TimestampStrategy.java b/src/main/java/com/github/f4b6a3/ulid/strategy/TimestampStrategy.java
similarity index 96%
rename from src/main/java/com/github/f4b6a3/ulid/timestamp/TimestampStrategy.java
rename to src/main/java/com/github/f4b6a3/ulid/strategy/TimestampStrategy.java
index 57f42f9..e6640b5 100644
--- a/src/main/java/com/github/f4b6a3/ulid/timestamp/TimestampStrategy.java
+++ b/src/main/java/com/github/f4b6a3/ulid/strategy/TimestampStrategy.java
@@ -22,7 +22,7 @@
  * SOFTWARE.
  */
 
-package com.github.f4b6a3.ulid.timestamp;
+package com.github.f4b6a3.ulid.strategy;
 
 public interface TimestampStrategy {
 	long getTimestamp();
diff --git a/src/main/java/com/github/f4b6a3/ulid/timestamp/DefaultTimestampStrategy.java b/src/main/java/com/github/f4b6a3/ulid/strategy/timestamp/DefaultTimestampStrategy.java
similarity index 92%
rename from src/main/java/com/github/f4b6a3/ulid/timestamp/DefaultTimestampStrategy.java
rename to src/main/java/com/github/f4b6a3/ulid/strategy/timestamp/DefaultTimestampStrategy.java
index d802ec0..2c9e514 100644
--- a/src/main/java/com/github/f4b6a3/ulid/timestamp/DefaultTimestampStrategy.java
+++ b/src/main/java/com/github/f4b6a3/ulid/strategy/timestamp/DefaultTimestampStrategy.java
@@ -22,7 +22,9 @@
  * SOFTWARE.
  */
 
-package com.github.f4b6a3.ulid.timestamp;
+package com.github.f4b6a3.ulid.strategy.timestamp;
+
+import com.github.f4b6a3.ulid.strategy.TimestampStrategy;
 
 public class DefaultTimestampStrategy implements TimestampStrategy {
 
diff --git a/src/main/java/com/github/f4b6a3/ulid/timestamp/FixedTimestampStretegy.java b/src/main/java/com/github/f4b6a3/ulid/strategy/timestamp/FixedTimestampStretegy.java
similarity index 92%
rename from src/main/java/com/github/f4b6a3/ulid/timestamp/FixedTimestampStretegy.java
rename to src/main/java/com/github/f4b6a3/ulid/strategy/timestamp/FixedTimestampStretegy.java
index 0d568f6..7b7e7a7 100644
--- a/src/main/java/com/github/f4b6a3/ulid/timestamp/FixedTimestampStretegy.java
+++ b/src/main/java/com/github/f4b6a3/ulid/strategy/timestamp/FixedTimestampStretegy.java
@@ -22,7 +22,9 @@
  * SOFTWARE.
  */
 
-package com.github.f4b6a3.ulid.timestamp;
+package com.github.f4b6a3.ulid.strategy.timestamp;
+
+import com.github.f4b6a3.ulid.strategy.TimestampStrategy;
 
 public class FixedTimestampStretegy implements TimestampStrategy {
 
diff --git a/src/main/java/com/github/f4b6a3/ulid/util/UlidConverter.java b/src/main/java/com/github/f4b6a3/ulid/util/UlidConverter.java
new file mode 100644
index 0000000..fecc005
--- /dev/null
+++ b/src/main/java/com/github/f4b6a3/ulid/util/UlidConverter.java
@@ -0,0 +1,103 @@
+/*
+ * MIT License
+ * 
+ * Copyright (c) 2020 Fabio Lima
+ * 
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ * 
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ * 
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package com.github.f4b6a3.ulid.util;
+
+import java.util.UUID;
+
+import com.github.f4b6a3.commons.util.Base32Util;
+import com.github.f4b6a3.commons.util.ByteUtil;
+
+public class UlidConverter {
+
+	private UlidConverter() {
+	}
+
+	/**
+	 * Convert a UUID to ULID string
+	 * 
+	 * The returning string is encoded to Crockford's base32.
+	 * 
+	 * The timestamp and random components are encoded separated.
+	 * 
+	 * @param uuid a UUID
+	 * @return a ULID
+	 */
+	public static String toString(UUID uuid) {
+
+		final long msb = uuid.getMostSignificantBits();
+		final long lsb = uuid.getLeastSignificantBits();
+
+		// Extract timestamp component
+		final long timeNumber = (msb >>> 16);
+		String timestampComponent = leftPad(Base32Util.toBase32Crockford(timeNumber));
+
+		// Extract randomness component
+		byte[] randBytes = new byte[10];
+		randBytes[0] = (byte) (msb >>> 8);
+		randBytes[1] = (byte) (msb);
+		byte[] lsbBytes = ByteUtil.toBytes(lsb);
+		System.arraycopy(lsbBytes, 0, randBytes, 2, 8);
+		String randomnessComponent = Base32Util.toBase32Crockford(randBytes);
+
+		return timestampComponent + randomnessComponent;
+	}
+
+	/**
+	 * Converts a ULID string to a UUID.
+	 * 
+	 * The input string must be encoded to Crockford's base32, following the ULID
+	 * specification.
+	 * 
+	 * The timestamp and random components are decoded separated.
+	 * 
+	 * An exception is thrown if the ULID string is invalid.
+	 * 
+	 * @param ulid a ULID
+	 * @return a UUID if valid
+	 */
+	public static UUID fromString(final String ulid) {
+
+		UlidValidator.validate(ulid);
+
+		// Extract timestamp component
+		final String timestampComponent = ulid.substring(0, 10);
+		final long timeNumber = Base32Util.fromBase32CrockfordAsLong(timestampComponent);
+
+		// Extract randomness component
+		final String randomnessComponent = ulid.substring(10, 26);
+		byte[] randBytes = Base32Util.fromBase32Crockford(randomnessComponent);
+		byte[] lsbBytes = new byte[8];
+		System.arraycopy(randBytes, 2, lsbBytes, 0, 8);
+
+		final long msb = (timeNumber << 16) | ((randBytes[0] << 8) & 0x0000ff00L) | ((randBytes[1]) & 0x000000ffL);
+		final long lsb = ByteUtil.toNumber(lsbBytes);
+
+		return new UUID(msb, lsb);
+	}
+
+	private static String leftPad(String unpadded) {
+		return "0000000000".substring(unpadded.length()) + unpadded;
+	}
+}
diff --git a/src/main/java/com/github/f4b6a3/ulid/util/UlidUtil.java b/src/main/java/com/github/f4b6a3/ulid/util/UlidUtil.java
index c40091d..57658eb 100644
--- a/src/main/java/com/github/f4b6a3/ulid/util/UlidUtil.java
+++ b/src/main/java/com/github/f4b6a3/ulid/util/UlidUtil.java
@@ -25,237 +25,16 @@
 package com.github.f4b6a3.ulid.util;
 
 import java.time.Instant;
-import java.util.UUID;
 
 import com.github.f4b6a3.commons.util.Base32Util;
-import com.github.f4b6a3.commons.util.ByteUtil;
 
 public class UlidUtil {
 
-	// Date: 10889-08-02T05:31:50.655Z
-	protected static final long TIMESTAMP_MAX = (long) Math.pow(2, 48) - 1;
-
-	protected static final String ULID_PATTERN_STRICT = "^[0-9a-hjkmnp-tv-zA-HJKMNP-TV-Z]{26}$";
-	protected static final String ULID_PATTERN_LOOSE = "^[0-9a-tv-zA-TV-Z]{26}$";
-
 	private UlidUtil() {
 	}
 
-	/**
-	 * Convert a UUID to ULID string
-	 * 
-	 * @param uuid
-	 *            a UUID
-	 * @return a ULID
-	 */
-	public static String fromUuidToUlid(UUID uuid) {
-
-		final long msb = uuid.getMostSignificantBits();
-		final long lsb = uuid.getLeastSignificantBits();
-
-		// Extract timestamp component
-		final long timeNumber = (msb >>> 16);
-		String timestampComponent = leftPad(Base32Util.toBase32Crockford(timeNumber));
-
-		// Extract randomness component
-		byte[] randBytes = new byte[10];
-		randBytes[0] = (byte) (msb >>> 8);
-		randBytes[1] = (byte) (msb);
-		byte[] lsbBytes = ByteUtil.toBytes(lsb);
-		System.arraycopy(lsbBytes, 0, randBytes, 2, 8);
-		String randomnessComponent = Base32Util.toBase32Crockford(randBytes);
-
-		return timestampComponent + randomnessComponent;
-	}
-
-	/**
-	 * Converts a ULID string to a UUID.
-	 * 
-	 * An exception is thrown if the ULID string is invalid.
-	 * 
-	 * @param ulid
-	 *            a ULID
-	 * @return a UUID if valid
-	 */
-	public static UUID fromUlidToUuid(final String ulid) {
-
-		UlidUtil.validate(ulid);
-
-		// Extract timestamp component
-		final String timestampComponent = ulid.substring(0, 10);
-		final long timeNumber = Base32Util.fromBase32CrockfordAsLong(timestampComponent);
-
-		// Extract randomness component
-		final String randomnessComponent = ulid.substring(10, 26);
-		byte[] randBytes = Base32Util.fromBase32Crockford(randomnessComponent);
-		byte[] lsbBytes = new byte[8];
-		System.arraycopy(randBytes, 2, lsbBytes, 0, 8);
-
-		final long msb = (timeNumber << 16) | ((randBytes[0] << 8) & 0x0000ff00L) | ((randBytes[1]) & 0x000000ffL);
-		final long lsb = ByteUtil.toNumber(lsbBytes);
-
-		return new UUID(msb, lsb);
-	}
-
-	/**
-	 * Get the array of bytes from a UUID.
-	 * 
-	 * @param uuid
-	 *            a UUID
-	 * @return an array of bytes
-	 */
-	public static byte[] fromUuidToBytes(final UUID uuid) {
-		final long msb = uuid.getMostSignificantBits();
-		final long lsb = uuid.getLeastSignificantBits();
-		final byte[] msbBytes = ByteUtil.toBytes(msb);
-		final byte[] lsbBytes = ByteUtil.toBytes(lsb);
-		return ByteUtil.concat(msbBytes, lsbBytes);
-	}
-
-	/**
-	 * Get a UUID from an array of bytes;
-	 * 
-	 * @param bytes
-	 *            an array of bytes
-	 * @return a UUID
-	 */
-	public static UUID fromBytesToUuid(byte[] bytes) {
-		byte[] msbBytes = new byte[8];
-		System.arraycopy(bytes, 0, msbBytes, 0, 8);
-		byte[] lsbBytes = new byte[8];
-		System.arraycopy(bytes, 8, lsbBytes, 0, 8);
-		final long msb = ByteUtil.toNumber(msbBytes);
-		final long lsb = ByteUtil.toNumber(lsbBytes);
-		return new UUID(msb, lsb);
-	}
-
-	/**
-	 * Convert an array of bytes to a ULID string.
-	 * 
-	 * @param bytes
-	 *            a byte array
-	 * @return a ULID string
-	 */
-	public static String fromBytesToUlid(byte[] bytes) {
-
-		byte[] timeBytes = new byte[6];
-		System.arraycopy(bytes, 0, timeBytes, 0, 6);
-		final long timeNumber = ByteUtil.toNumber(timeBytes);
-		final String timestampComponent = leftPad(Base32Util.toBase32Crockford(timeNumber));
-
-		byte[] randBytes = new byte[10];
-		System.arraycopy(bytes, 6, randBytes, 0, 10);
-		final String randomnessComponent = Base32Util.toBase32Crockford(randBytes);
-
-		return timestampComponent + randomnessComponent;
-	}
-
-	/**
-	 * Convert a ULID string to an array of bytes.
-	 * 
-	 * @param ulid
-	 *            a ULID string
-	 * @return an array of bytes
-	 */
-	public static byte[] fromUlidToBytes(final String ulid) {
-		UlidUtil.validate(ulid);
-		byte[] bytes = new byte[16];
-
-		final String timestampComponent = ulid.substring(0, 10);
-		final long timeNumber = Base32Util.fromBase32CrockfordAsLong(timestampComponent);
-		byte[] timeBytes = ByteUtil.toBytes(timeNumber);
-		System.arraycopy(timeBytes, 2, bytes, 0, 6);
-
-		final String randomnessComponent = ulid.substring(10, 26);
-		byte[] randBytes = Base32Util.fromBase32Crockford(randomnessComponent);
-		System.arraycopy(randBytes, 0, bytes, 6, 10);
-
-		return bytes;
-	}
-
-	/**
-	 * Checks if the ULID string is a valid.
-	 * 
-	 * The validation mode is not strict.
-	 * 
-	 * See {@link UlidUtil#validate(String, boolean)}.
-	 * 
-	 * @param ulid
-	 *            a ULID
-	 */
-	protected static void validate(String ulid) {
-		validate(ulid, false);
-	}
-
-	/**
-	 * Checks if the ULID string is a valid.
-	 * 
-	 * See {@link UlidUtil#validate(String, boolean)}.
-	 * 
-	 * @param ulid
-	 *            a ULID
-	 */
-	protected static void validate(String ulid, boolean strict) {
-		if (!isValid(ulid, strict)) {
-			throw new UlidUtilException(String.format("Invalid ULID: %s.", ulid));
-		}
-	}
-
-	/**
-	 * Checks if the string is a valid ULID.
-	 * 
-	 * The validation mode is not strict.
-	 * 
-	 * See {@link UlidUtil#validate(String, boolean)}.
-	 */
-	public static boolean isValid(String ulid) {
-		return isValid(ulid, false);
-	}
-
-	/**
-	 * Checks if the string is a valid ULID.
-	 * 
-	 * <pre>
-	 * Strict validation: checks if the string is in the ULID specification format:
-	 * 
-	 * - 0123456789ABCDEFGHJKMNPKRS (26 alphanumeric, case insensitive, except iI, lL, oO and uU)
-	 * 
-	 * Loose validation: checks if the string is in one of these formats:
-	 *
-	 * - 0123456789ABCDEFGHIJKLMNOP (26 alphanumeric, case insensitive, except uU)
-	 * </pre>
-	 * 
-	 * @param ulid
-	 *            a ULID
-	 * @param strict
-	 *            true for strict validation, false for loose validation
-	 * @return boolean true if valid
-	 */
-	public static boolean isValid(String ulid, boolean strict) {
-
-		if (ulid == null || ulid.isEmpty()) {
-			return false;
-		}
-
-		boolean matches = false;
-
-		if (strict) {
-			matches = ulid.matches(ULID_PATTERN_STRICT);
-		} else {
-			String u = ulid.replaceAll("-", "");
-			matches = u.matches(ULID_PATTERN_LOOSE);
-		}
-
-		if (!matches) {
-			return false;
-		}
-
-		long timestamp = extractUnixMilliseconds(ulid);
-		return timestamp >= 0 && timestamp <= TIMESTAMP_MAX;
-	}
-
 	public static long extractTimestamp(String ulid) {
-		UlidUtil.validate(ulid);
+		UlidValidator.validate(ulid);
 		return extractUnixMilliseconds(ulid);
 	}
 
@@ -265,12 +44,12 @@ public class UlidUtil {
 	}
 
 	public static String extractTimestampComponent(String ulid) {
-		UlidUtil.validate(ulid);
+		UlidValidator.validate(ulid);
 		return ulid.substring(0, 10);
 	}
 
 	public static String extractRandomnessComponent(String ulid) {
-		UlidUtil.validate(ulid);
+		UlidValidator.validate(ulid);
 		return ulid.substring(10, 26);
 	}
 
@@ -278,16 +57,4 @@ public class UlidUtil {
 		String milliseconds = ulid.substring(0, 10);
 		return Base32Util.fromBase32CrockfordAsLong(milliseconds);
 	}
-
-	private static String leftPad(String unpadded) {
-		return "0000000000".substring(unpadded.length()) + unpadded;
-	}
-
-	public static class UlidUtilException extends RuntimeException {
-		private static final long serialVersionUID = 1L;
-
-		public UlidUtilException(String message) {
-			super(message);
-		}
-	}
 }
diff --git a/src/main/java/com/github/f4b6a3/ulid/util/UlidValidator.java b/src/main/java/com/github/f4b6a3/ulid/util/UlidValidator.java
new file mode 100644
index 0000000..1d4d916
--- /dev/null
+++ b/src/main/java/com/github/f4b6a3/ulid/util/UlidValidator.java
@@ -0,0 +1,87 @@
+/*
+ * MIT License
+ * 
+ * Copyright (c) 2020 Fabio Lima
+ * 
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ * 
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ * 
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package com.github.f4b6a3.ulid.util;
+
+import com.github.f4b6a3.ulid.exception.InvalidUlidException;
+
+public class UlidValidator {
+
+	protected static final String ULID_PATTERN = "^[0-9a-tv-zA-TV-Z]{26}$";
+
+	// Date: 10889-08-02T05:31:50.655Z
+	protected static final long TIMESTAMP_MAX = (long) Math.pow(2, 48) - 1;
+
+	private UlidValidator() {
+	}
+
+	/**
+	 * Checks if the string is a valid ULID.
+	 * 
+	 * A valid ULID string is a sequence of 26 characters from Crockford's base 32
+	 * alphabet.
+	 * 
+	 * Dashes are ignored by this validator.
+	 * 
+	 * <pre>
+	 * Examples of valid ULID strings:
+	 * - 0123456789ABCDEFGHJKMNPKRS (26 alphanumeric, case insensitive, except iI, lL, oO and uU)
+	 * - 0123456789ABCDEFGHIJKLMNOP (26 alphanumeric, case insensitive, except uU)
+	 * - 0123456789-ABCDEFGHJK-MNPKRS (26 alphanumeric, case insensitive, except iI, lL, oO and uU)
+	 * - 0123456789-ABCDEFGHIJ-KLMNOP (26 alphanumeric, case insensitive, except uU, with dashes)
+	 * </pre>
+	 * 
+	 * @param ulid a ULID
+	 * @return boolean true if valid
+	 */
+	public static boolean isValid(String ulid) {
+
+		if (ulid == null || ulid.isEmpty()) {
+			return false;
+		}
+
+		String u = ulid.replaceAll("-", "");
+		if (!u.matches(ULID_PATTERN)) {
+			return false;
+		}
+
+		long timestamp = UlidUtil.extractUnixMilliseconds(ulid);
+		return timestamp >= 0 && timestamp <= TIMESTAMP_MAX;
+
+	}
+
+	/**
+	 * Checks if the ULID string is a valid.
+	 * 
+	 * See {@link TsidValidator#isValid(String)}.
+	 * 
+	 * @param ulid a ULID string
+	 * @throws InvalidUlidException if invalid
+	 */
+	protected static void validate(String ulid) {
+		if (!isValid(ulid)) {
+			throw new InvalidUlidException(String.format("Invalid ULID: %s.", ulid));
+		}
+	}
+}
diff --git a/src/test/java/com/github/f4b6a3/TestSuite.java b/src/test/java/com/github/f4b6a3/ulid/TestSuite.java
similarity index 63%
rename from src/test/java/com/github/f4b6a3/TestSuite.java
rename to src/test/java/com/github/f4b6a3/ulid/TestSuite.java
index 1b8b62f..c5cdfee 100644
--- a/src/test/java/com/github/f4b6a3/TestSuite.java
+++ b/src/test/java/com/github/f4b6a3/ulid/TestSuite.java
@@ -1,19 +1,21 @@
-package com.github.f4b6a3;
+package com.github.f4b6a3.ulid;
 
 import org.junit.runner.RunWith;
 import org.junit.runners.Suite;
 
-import com.github.f4b6a3.ulid.UlidCreatorTest;
 import com.github.f4b6a3.ulid.creator.UlidBasedGuidCreatorTest;
-import com.github.f4b6a3.ulid.timestamp.DefaultTimestampStrategyTest;
+import com.github.f4b6a3.ulid.ulid.UlidCreatorTest;
+import com.github.f4b6a3.ulid.util.UlidConverterTest;
 import com.github.f4b6a3.ulid.util.UlidUtilTest;
+import com.github.f4b6a3.ulid.util.UlidValidatorTest;
 
 @RunWith(Suite.class)
 @Suite.SuiteClasses({
-   DefaultTimestampStrategyTest.class,
-   UlidBasedGuidCreatorTest.class,
-   UlidUtilTest.class,
    UlidCreatorTest.class,
+   UlidBasedGuidCreatorTest.class,
+   UlidConverterTest.class,
+   UlidUtilTest.class,
+   UlidValidatorTest.class,
 })
 
 /**
diff --git a/src/test/java/com/github/f4b6a3/UniquenessTest.java b/src/test/java/com/github/f4b6a3/ulid/UniquenessTest.java
similarity index 97%
rename from src/test/java/com/github/f4b6a3/UniquenessTest.java
rename to src/test/java/com/github/f4b6a3/ulid/UniquenessTest.java
index ea00a26..dbb33c4 100644
--- a/src/test/java/com/github/f4b6a3/UniquenessTest.java
+++ b/src/test/java/com/github/f4b6a3/ulid/UniquenessTest.java
@@ -1,4 +1,4 @@
-package com.github.f4b6a3;
+package com.github.f4b6a3.ulid;
 
 import java.util.HashSet;
 import java.util.UUID;
@@ -6,7 +6,7 @@ import java.util.UUID;
 import com.github.f4b6a3.ulid.UlidCreator;
 import com.github.f4b6a3.ulid.creator.UlidBasedGuidCreator;
 import com.github.f4b6a3.ulid.exception.UlidCreatorException;
-import com.github.f4b6a3.ulid.timestamp.FixedTimestampStretegy;
+import com.github.f4b6a3.ulid.strategy.timestamp.FixedTimestampStretegy;
 
 /**
  * 
diff --git a/src/test/java/com/github/f4b6a3/Benchmarks.java b/src/test/java/com/github/f4b6a3/ulid/bench/Benchmarks.java
similarity index 98%
rename from src/test/java/com/github/f4b6a3/Benchmarks.java
rename to src/test/java/com/github/f4b6a3/ulid/bench/Benchmarks.java
index 2eddf2e..7bbd0f1 100644
--- a/src/test/java/com/github/f4b6a3/Benchmarks.java
+++ b/src/test/java/com/github/f4b6a3/ulid/bench/Benchmarks.java
@@ -1,4 +1,4 @@
-package com.github.f4b6a3;
+package com.github.f4b6a3.ulid.bench;
 
 // Add theese dependencies to pom.xml:
 //
diff --git a/src/test/java/com/github/f4b6a3/ulid/creator/UlidBasedGuidCreatorTest.java b/src/test/java/com/github/f4b6a3/ulid/creator/UlidBasedGuidCreatorTest.java
index 9068805..af6794f 100644
--- a/src/test/java/com/github/f4b6a3/ulid/creator/UlidBasedGuidCreatorTest.java
+++ b/src/test/java/com/github/f4b6a3/ulid/creator/UlidBasedGuidCreatorTest.java
@@ -7,7 +7,7 @@ import org.junit.Test;
 
 import com.github.f4b6a3.commons.random.Xorshift128PlusRandom;
 import com.github.f4b6a3.ulid.exception.UlidCreatorException;
-import com.github.f4b6a3.ulid.timestamp.FixedTimestampStretegy;
+import com.github.f4b6a3.ulid.strategy.timestamp.FixedTimestampStretegy;
 
 import static org.junit.Assert.*;
 
diff --git a/src/test/java/com/github/f4b6a3/demo/DemoTest.java b/src/test/java/com/github/f4b6a3/ulid/demo/DemoTest.java
similarity index 83%
rename from src/test/java/com/github/f4b6a3/demo/DemoTest.java
rename to src/test/java/com/github/f4b6a3/ulid/demo/DemoTest.java
index c46baca..ed951e2 100644
--- a/src/test/java/com/github/f4b6a3/demo/DemoTest.java
+++ b/src/test/java/com/github/f4b6a3/ulid/demo/DemoTest.java
@@ -1,4 +1,4 @@
-package com.github.f4b6a3.demo;
+package com.github.f4b6a3.ulid.demo;
 
 import com.github.f4b6a3.ulid.UlidCreator;
 
@@ -10,7 +10,7 @@ public class DemoTest {
 		int max = 100;
 
 		System.out.println(HORIZONTAL_LINE);
-		System.out.println("### ULID");
+		System.out.println("### ULID string");
 		System.out.println(HORIZONTAL_LINE);
 
 		for (int i = 0; i < max; i++) {
@@ -18,7 +18,7 @@ public class DemoTest {
 		}
 
 		System.out.println(HORIZONTAL_LINE);
-		System.out.println("### GUID");
+		System.out.println("### ULID-based GUID");
 		System.out.println(HORIZONTAL_LINE);
 
 		for (int i = 0; i < max; i++) {
diff --git a/src/test/java/com/github/f4b6a3/ulid/timestamp/DefaultTimestampStrategyTest.java b/src/test/java/com/github/f4b6a3/ulid/timestamp/DefaultTimestampStrategyTest.java
deleted file mode 100644
index 5b8d251..0000000
--- a/src/test/java/com/github/f4b6a3/ulid/timestamp/DefaultTimestampStrategyTest.java
+++ /dev/null
@@ -1,12 +0,0 @@
-package com.github.f4b6a3.ulid.timestamp;
-
-import static org.junit.Assert.assertTrue;
-
-import org.junit.Test;
-
-public class DefaultTimestampStrategyTest {
-	@Test
-	public void testVoid() {
-		assertTrue("void test", true);
-	}
-}
diff --git a/src/test/java/com/github/f4b6a3/ulid/UlidCreatorTest.java b/src/test/java/com/github/f4b6a3/ulid/ulid/UlidCreatorTest.java
similarity index 95%
rename from src/test/java/com/github/f4b6a3/ulid/UlidCreatorTest.java
rename to src/test/java/com/github/f4b6a3/ulid/ulid/UlidCreatorTest.java
index c16389d..0d732f5 100644
--- a/src/test/java/com/github/f4b6a3/ulid/UlidCreatorTest.java
+++ b/src/test/java/com/github/f4b6a3/ulid/ulid/UlidCreatorTest.java
@@ -1,4 +1,4 @@
-package com.github.f4b6a3.ulid;
+package com.github.f4b6a3.ulid.ulid;
 
 import org.junit.BeforeClass;
 import org.junit.Test;
@@ -6,6 +6,7 @@ import org.junit.Test;
 import com.github.f4b6a3.ulid.UlidCreator;
 import com.github.f4b6a3.ulid.creator.UlidBasedGuidCreator;
 import com.github.f4b6a3.ulid.util.UlidUtil;
+import com.github.f4b6a3.ulid.util.UlidValidator;
 
 import static org.junit.Assert.*;
 import java.util.Arrays;
@@ -54,7 +55,7 @@ public class UlidCreatorTest {
 			assertTrue("ULID is null", ulid != null);
 			assertTrue("ULID is empty", !ulid.isEmpty());
 			assertTrue("ULID length is wrong ", ulid.length() == ULID_LENGTH);
-			assertTrue("ULID is not valid", UlidUtil.isValid(ulid, /* strict */ true));
+			assertTrue("ULID is not valid", UlidValidator.isValid(ulid));
 		}
 	}
 
diff --git a/src/test/java/com/github/f4b6a3/ulid/util/UlidConverterTest.java b/src/test/java/com/github/f4b6a3/ulid/util/UlidConverterTest.java
new file mode 100644
index 0000000..7199d76
--- /dev/null
+++ b/src/test/java/com/github/f4b6a3/ulid/util/UlidConverterTest.java
@@ -0,0 +1,35 @@
+package com.github.f4b6a3.ulid.util;
+
+import static org.junit.Assert.*;
+import java.util.UUID;
+
+import org.junit.Test;
+
+import com.github.f4b6a3.ulid.UlidCreator;
+import com.github.f4b6a3.ulid.util.UlidConverter;
+import com.github.f4b6a3.ulid.util.UlidValidator;
+
+public class UlidConverterTest {
+
+	private static final int ULID_LENGTH = 26;
+	private static final int DEFAULT_LOOP_MAX = 100_000;
+
+	@Test
+	public void testToAndFromUlid() {
+
+		for (int i = 0; i < DEFAULT_LOOP_MAX; i++) {
+
+			UUID uuid1 = UlidCreator.getUlid();
+			String ulid = UlidConverter.toString(uuid1);
+
+			assertTrue("ULID is null", ulid != null);
+			assertTrue("ULID is empty", !ulid.isEmpty());
+			assertTrue("ULID length is wrong ", ulid.length() == ULID_LENGTH);
+			assertTrue("ULID is not valid", UlidValidator.isValid(ulid));
+
+			UUID uuid2 = UlidConverter.fromString(ulid);
+			assertEquals("Result ULID is different from original ULID", uuid1, uuid2);
+
+		}
+	}
+}
diff --git a/src/test/java/com/github/f4b6a3/ulid/util/UlidUtilTest.java b/src/test/java/com/github/f4b6a3/ulid/util/UlidUtilTest.java
index e41b7a1..173af03 100644
--- a/src/test/java/com/github/f4b6a3/ulid/util/UlidUtilTest.java
+++ b/src/test/java/com/github/f4b6a3/ulid/util/UlidUtilTest.java
@@ -2,14 +2,13 @@ package com.github.f4b6a3.ulid.util;
 
 import static org.junit.Assert.*;
 import java.time.Instant;
-import java.util.UUID;
 
 import org.junit.Test;
 
-import com.github.f4b6a3.ulid.util.UlidUtil.UlidUtilException;
 import com.github.f4b6a3.commons.util.Base32Util;
 import com.github.f4b6a3.commons.util.ByteUtil;
-import com.github.f4b6a3.ulid.UlidCreator;
+import com.github.f4b6a3.ulid.exception.InvalidUlidException;
+import com.github.f4b6a3.ulid.util.UlidUtil;
 
 public class UlidUtilTest {
 
@@ -19,13 +18,10 @@ public class UlidUtilTest {
 
 	private static final long TIMESTAMP_MAX = 281474976710655l; // 2^48 - 1
 
-	private static final int ULID_LENGTH = 26;
-	private static final int DEFAULT_LOOP_MAX = 100_000;
-
 	private static final String[] EXAMPLE_DATES = { "1970-01-01T00:00:00.000Z", "1985-10-26T01:16:00.123Z",
 			"2001-09-09T01:46:40.456Z", "2020-01-15T14:30:33.789Z", "2038-01-19T03:14:07.321Z" };
 
-	@Test(expected = UlidUtilException.class)
+	@Test(expected = InvalidUlidException.class)
 	public void testExtractTimestamp() {
 
 		String ulid = "0000000000" + EXAMPLE_RANDOMNESS;
@@ -95,155 +91,6 @@ public class UlidUtilTest {
 		assertEquals(expected, result);
 	}
 
-	@Test
-	public void testIsValidLoose() {
-
-		String ulid = null; // Null
-		assertFalse("Null ULID should be invalid.", UlidUtil.isValid(ulid));
-
-		ulid = ""; // length: 0
-		assertFalse("ULID with empty string should be invalid.", UlidUtil.isValid(ulid));
-
-		ulid = EXAMPLE_ULID; // All upper case
-		assertTrue("Ulid in upper case should valid.", UlidUtil.isValid(ulid));
-
-		ulid = "0123456789abcdefghjklmnpqr"; // All lower case
-		assertTrue("ULID in lower case should be valid.", UlidUtil.isValid(ulid));
-
-		ulid = "0123456789AbCdEfGhJkMnPqRs"; // Mixed case
-		assertTrue("Ulid in upper and lower case should valid.", UlidUtil.isValid(ulid));
-
-		ulid = "0123456789ABCDEFGHJKLMNPQ"; // length: 25
-		assertFalse("ULID length lower than 26 should be invalid.", UlidUtil.isValid(ulid));
-
-		ulid = "0123456789ABCDEFGHJKMNPQZZZ"; // length: 27
-		assertFalse("ULID length greater than 26 should be invalid.", UlidUtil.isValid(ulid));
-
-		ulid = "u123456789ABCDEFGHJKMNPQRS"; // Letter u
-		assertFalse("ULID with 'u' or 'U' should be invalid.", UlidUtil.isValid(ulid));
-
-		ulid = "#123456789ABCDEFGHJKMNPQRS"; // Special char
-		assertFalse("ULID with special chars should be invalid.", UlidUtil.isValid(ulid));
-
-		ulid = "01234-56789-ABCDEFGHJKMNPQRS"; // Hiphens
-		assertTrue("ULID with hiphens should be valid.", UlidUtil.isValid(ulid));
-
-		ulid = "8ZZZZZZZZZABCDEFGHJKMNPQRS"; // timestamp > (2^48)-1
-		assertFalse("ULID with timestamp greater than (2^48)-1 should be invalid.", UlidUtil.isValid(ulid));
-	}
-
-	@Test
-	public void testIsValidStrict() {
-		boolean strict = true;
-
-		String ulid = null; // Null
-		assertFalse("Null ULID should be invalid in strict mode.", UlidUtil.isValid(ulid, strict));
-
-		ulid = ""; // length: 0
-		assertFalse("ULID with empty string should be invalid  in strict mode.", UlidUtil.isValid(ulid, strict));
-
-		ulid = EXAMPLE_ULID; // All upper case
-		assertTrue("ULID in upper case should valid in strict mode.", UlidUtil.isValid(ulid, strict));
-
-		ulid = "0123456789abcdefghjkmnpqrs"; // All lower case
-		assertTrue("ULID in lower case should be valid in strict mode.", UlidUtil.isValid(ulid, strict));
-
-		ulid = "0123456789AbCdEfGhJkMnPqRs"; // Mixed case
-		assertTrue("ULID in upper and lower case should valid in strict mode.", UlidUtil.isValid(ulid, strict));
-
-		ulid = "0123456789ABCDEFGHJKLMNPQ"; // length: 25
-		assertFalse("ULID length lower than 26 should be invalid in strict mode.", UlidUtil.isValid(ulid, strict));
-
-		ulid = "0123456789ABCDEFGHJKMNPQZZZ"; // length: 27
-		assertFalse("ULID length greater than 26 should be invalid in strict mode.", UlidUtil.isValid(ulid, strict));
-
-		ulid = "i123456789ABCDEFGHJKMNPQRS"; // Letter i
-		assertFalse("ULID with 'i' or 'I' should be invalid in strict mode.", UlidUtil.isValid(ulid, strict));
-
-		ulid = "L123456789ABCDEFGHJKMNPQRS"; // letter L
-		assertFalse("ULID with 'l' or 'L' should be invalid in strict mode.", UlidUtil.isValid(ulid, strict));
-
-		ulid = "o123456789ABCDEFGHJKMNPQRS"; // letter o
-		assertFalse("ULID with 'o' or 'O' should be invalid in strict mode.", UlidUtil.isValid(ulid, strict));
-
-		ulid = "u123456789ABCDEFGHJKMNPQRS"; // letter u
-		assertFalse("ULID with 'u' or 'U' should be invalid in strict mode.", UlidUtil.isValid(ulid, strict));
-
-		ulid = "#123456789ABCDEFGHJKMNPQRS"; // Special char
-		assertFalse("ULID with special chars should be invalid in strict mode.", UlidUtil.isValid(ulid, strict));
-
-		ulid = "01234-56789-ABCDEFGHJKMNPQRS"; // Hyphens
-		assertFalse("ULID with hiphens should be invalid in strict mode.", UlidUtil.isValid(ulid, strict));
-
-		ulid = "8ZZZZZZZZZABCDEFGHJKMNPQRS"; // timestamp > (2^48)-1
-		assertFalse("ULID with timestamp greater than (2^48)-1 should be invalid.", UlidUtil.isValid(ulid));
-	}
-
-	@Test
-	public void testToAndFromUlid() {
-
-		for (int i = 0; i < DEFAULT_LOOP_MAX; i++) {
-
-			UUID uuid1 = UlidCreator.getUlid();
-			String ulid = UlidUtil.fromUuidToUlid(uuid1);
-
-			assertTrue("ULID is null", ulid != null);
-			assertTrue("ULID is empty", !ulid.isEmpty());
-			assertTrue("ULID length is wrong ", ulid.length() == ULID_LENGTH);
-			assertTrue("ULID is not valid", UlidUtil.isValid(ulid, /* strict */
-					true));
-
-			UUID uuid2 = UlidUtil.fromUlidToUuid(ulid);
-			assertEquals("Result ULID is different from original ULID", uuid1, uuid2);
-
-		}
-	}
-
-	@Test
-	public void testToAndFromBytes() {
-		for (int i = 0; i < DEFAULT_LOOP_MAX; i++) {
-			String ulid1 = UlidCreator.getUlidString();
-			byte[] bytes = UlidUtil.fromUlidToBytes(ulid1);
-			String ulid2 = UlidUtil.fromBytesToUlid(bytes);
-
-			// Check ULID 1
-			assertTrue(ulid1 != null);
-			assertTrue(!ulid1.isEmpty());
-			assertTrue(ulid1.length() == ULID_LENGTH);
-			assertTrue(UlidUtil.isValid(ulid1, /* strict */ true));
-
-			// Check ULID 2
-			assertTrue(ulid2 != null);
-			assertTrue(!ulid2.isEmpty());
-			assertTrue(ulid2.length() == ULID_LENGTH);
-			assertTrue(UlidUtil.isValid(ulid2, /* strict */ true));
-
-			assertEquals(ulid1, ulid2);
-		}
-	}
-
-	@Test
-	public void testFromUuidToBytes() {
-		for (int i = 0; i < DEFAULT_LOOP_MAX; i++) {
-			UUID uuid1 = UlidCreator.getUlid();
-			byte[] bytes = UlidUtil.fromUuidToBytes(uuid1);
-			long msb = ByteUtil.toNumber(ByteUtil.copy(bytes, 0, 8));
-			long lsb = ByteUtil.toNumber(ByteUtil.copy(bytes, 8, 16));
-			UUID uuid2 = new UUID(msb, lsb);
-			assertEquals(uuid1, uuid2);
-		}
-	}
-
-	@Test
-	public void testFromBytesToUuid() {
-		for (int i = 0; i < DEFAULT_LOOP_MAX; i++) {
-			UUID uuid1 = UlidCreator.getUlid();
-			byte[] bytes = UlidUtil.fromUuidToBytes(uuid1);
-			UUID uuid2 = UlidUtil.fromBytesToUuid(bytes);
-			assertEquals(uuid1, uuid2);
-		}
-	}
-
 	private String leftPad(String unpadded) {
 		return "0000000000".substring(unpadded.length()) + unpadded;
 	}
diff --git a/src/test/java/com/github/f4b6a3/ulid/util/UlidValidatorTest.java b/src/test/java/com/github/f4b6a3/ulid/util/UlidValidatorTest.java
new file mode 100644
index 0000000..936ab01
--- /dev/null
+++ b/src/test/java/com/github/f4b6a3/ulid/util/UlidValidatorTest.java
@@ -0,0 +1,47 @@
+package com.github.f4b6a3.ulid.util;
+
+import static org.junit.Assert.*;
+
+import org.junit.Test;
+
+import com.github.f4b6a3.ulid.util.UlidValidator;
+
+public class UlidValidatorTest {
+
+	@Test
+	public void testIsValidStrict() {
+
+		String ulid = null; // Null
+		assertFalse("Null ULID should be invalid.", UlidValidator.isValid(ulid));
+
+		ulid = ""; // length: 0
+		assertFalse("ULID with empty string should be invalid .", UlidValidator.isValid(ulid));
+
+		ulid = "0123456789ABCDEFGHJKMNPQRS"; // All upper case
+		assertTrue("ULID in upper case should valid.", UlidValidator.isValid(ulid));
+
+		ulid = "0123456789abcdefghjklmnpqr"; // All lower case
+		assertTrue("ULID in lower case should be valid.", UlidValidator.isValid(ulid));
+
+		ulid = "0123456789AbCdEfGhJkMnPqRs"; // Mixed case
+		assertTrue("Ulid in upper and lower case should valid.", UlidValidator.isValid(ulid));
+
+		ulid = "0123456789ABCDEFGHJKLMNPQ"; // length: 25
+		assertFalse("ULID length lower than 26 should be invalid.", UlidValidator.isValid(ulid));
+
+		ulid = "0123456789ABCDEFGHJKMNPQZZZ"; // length: 27
+		assertFalse("ULID length greater than 26 should be invalid.", UlidValidator.isValid(ulid));
+
+		ulid = "u123456789ABCDEFGHJKMNPQRS"; // Letter u
+		assertFalse("ULID with 'u' or 'U' should be invalid.", UlidValidator.isValid(ulid));
+
+		ulid = "#123456789ABCDEFGHJKMNPQRS"; // Special char
+		assertFalse("ULID with special chars should be invalid.", UlidValidator.isValid(ulid));
+
+		ulid = "01234-56789-ABCDEFGHJKMNPQRS"; // Hyphens
+		assertTrue("ULID with hiphens should be valid.", UlidValidator.isValid(ulid));
+
+		ulid = "8ZZZZZZZZZABCDEFGHJKMNPQRS"; // timestamp > (2^48)-1
+		assertFalse("ULID with timestamp greater than (2^48)-1 should be invalid.", UlidValidator.isValid(ulid));
+	}
+}