diff --git a/.gitignore b/.gitignore
index e0d53d8..7e762bc 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,4 @@
 .gradle
 .idea
 build
+local.properties
diff --git a/build.gradle b/build.gradle
index 70bf368..2322d69 100644
--- a/build.gradle
+++ b/build.gradle
@@ -1,34 +1,44 @@
 plugins {
-  id "org.jetbrains.kotlin.jvm" version '1.1.2-2'
-  id "com.jfrog.bintray" version "1.7.3"
+  id "org.jetbrains.kotlin.jvm" version "1.7.20"
+  id "com.palantir.git-version" version "0.15.0"
   id "maven-publish"
 }
 
-group 'th.or.nectec'
-version = {->
-  def stdout = new ByteArrayOutputStream()
-  exec {
-    commandLine 'git', 'describe', '--tags'
-    standardOutput = stdout
-  }
-  return stdout.toString().trim()
-}.call()
+group "th.or.nectec"
+version = versionDetails().lastTag
 
-sourceCompatibility = 1.7
-targetCompatibility = 1.7
+ext {
+  libraryName = "Thai Units"
+  libraryDescription = "Kotlin library for handle Thai units of measurement"
+
+  groupId = "com.github.nectec-opensource"
+  artifactId = "thai-unit"
+
+  siteUrl = "https://github.com/${project.githubRepo}"
+  gitUrl = "https://github.com/${project.githubRepo}.git"
+
+  developerId = 'piruin'
+  developName = 'Piruin Panichphol'
+  developerEmail = 'piruin.panichphol@nectec.or.th'
+
+  licenseName = "The Apache License, Version 2.0"
+  licenseUrl = "http://www.apache.org/licenses/LICENSE-2.0.txt"
+}
+
+sourceCompatibility = 1.8
+targetCompatibility = 1.8
 
 repositories {
-  jcenter()
+  mavenCentral()
 }
 
 dependencies {
-  def kotlinVersion = '1.1.2'
+  def kotlinVersion = "1.7.20"
 
-  compile "org.jetbrains.kotlin:kotlin-stdlib-jre7:$kotlinVersion"
+  implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlinVersion"
 
-  testCompile 'junit:junit:4.12'
-  testCompile "org.jetbrains.kotlin:kotlin-test-junit:$kotlinVersion"
-  testCompile "com.google.code.gson:gson:2.8.1"
+  testImplementation "junit:junit:4.13.2"
+  testImplementation "com.google.code.gson:gson:2.10"
 }
 
-apply from: 'bintray.gradle'
+apply from: './publish/mavencentral.gradle'
diff --git a/gradle/wrapper/gradle-wrapper.properties b/gradle/wrapper/gradle-wrapper.properties
index 2a6ca58..ae04661 100644
--- a/gradle/wrapper/gradle-wrapper.properties
+++ b/gradle/wrapper/gradle-wrapper.properties
@@ -1,6 +1,5 @@
-#Tue Jun 06 14:02:38 ICT 2017
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-7.5.1-bin.zip
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-3.3-bin.zip
diff --git a/publish/mavencentral.gradle b/publish/mavencentral.gradle
new file mode 100644
index 0000000..1718a8c
--- /dev/null
+++ b/publish/mavencentral.gradle
@@ -0,0 +1,81 @@
+apply plugin: 'maven-publish'
+apply plugin: 'signing'
+
+group = project.groupId
+version = project.version
+
+ext["ossrhUsername"] = ''
+ext["ossrhPassword"] = ''
+
+File secretPropsFile = project.rootProject.file('local.properties')
+if (secretPropsFile.exists()) {
+  Properties p = new Properties()
+  p.load(new FileInputStream(secretPropsFile))
+  p.each { name, value ->
+    ext[name] = value
+  }
+} else {
+  ext["ossrhUsername"] = System.getenv('OSSRH_USERNAME')
+  ext["ossrhPassword"] = System.getenv('OSSRH_PASSWORD')
+}
+
+publishing {
+  publications {
+    release(MavenPublication) {
+      groupId project.groupId
+      artifactId project.artifactId
+      version project.version
+
+      artifact("$buildDir/libs/${project.getName()}-${version}.jar")
+
+      pom {
+        name = project.libraryName
+        description = project.libraryDescription
+        url = project.siteUrl
+        licenses {
+          license {
+            name = project.licenseName
+            url = project.licenseUrl
+          }
+        }
+        developers {
+          developer {
+            id = project.developerId
+            name = project.developName
+            email = project.developerEmail
+          }
+        }
+        scm {
+          connection = project.gitUrl
+          developerConnection = project.gitUrl
+          url = project.siteUrl
+        }
+        withXml {
+          def dependenciesNode = asNode().appendNode('dependencies')
+          project.configurations.implementation.allDependencies.each {
+            if (it.name != 'unspecified') {
+              def dependencyNode = dependenciesNode.appendNode('dependency')
+              dependencyNode.appendNode('groupId', it.group)
+              dependencyNode.appendNode('artifactId', it.name)
+              dependencyNode.appendNode('version', it.version)
+            }
+          }
+        }
+      }
+    }
+  }
+  repositories {
+    maven {
+      name = "sonatype"
+      url = "https://s01.oss.sonatype.org/service/local/staging/deploy/maven2/"
+      credentials {
+        username ossrhUsername
+        password ossrhPassword
+      }
+    }
+  }
+}
+
+signing {
+  sign publishing.publications
+}
diff --git a/src/main/kotlin/nectec/thai/unit/Area.kt b/src/main/kotlin/nectec/thai/unit/Area.kt
index c72c08c..8962e50 100644
--- a/src/main/kotlin/nectec/thai/unit/Area.kt
+++ b/src/main/kotlin/nectec/thai/unit/Area.kt
@@ -18,6 +18,7 @@
 package nectec.thai.unit
 
 import java.lang.StringBuilder
+import kotlin.math.floor
 
 data class Area(val squareMetre: Double) : Comparable<Area> {
 
@@ -97,7 +98,7 @@ data class Area(val squareMetre: Double) : Comparable<Area> {
     }
   }
 
-  fun Double.round(): Any {
-    return if (this == Math.floor(this)) this.toInt() else this.toString()
+  private fun Double.round(): Any {
+    return if (this == floor(this)) this.toInt() else this.toString()
   }
 }
diff --git a/src/test/kotlin/nectec/thai/unit/AreaJavaTest.java b/src/test/kotlin/nectec/thai/unit/AreaJavaTest.kt
similarity index 74%
rename from src/test/kotlin/nectec/thai/unit/AreaJavaTest.java
rename to src/test/kotlin/nectec/thai/unit/AreaJavaTest.kt
index 4f1478a..7c8bd89 100644
--- a/src/test/kotlin/nectec/thai/unit/AreaJavaTest.java
+++ b/src/test/kotlin/nectec/thai/unit/AreaJavaTest.kt
@@ -14,17 +14,15 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+package nectec.thai.unit
 
-package nectec.thai.unit;
-
-import org.junit.Assert;
-import org.junit.Test;
-
-public class AreaJavaTest {
+import org.junit.Assert.assertEquals
+import org.junit.Test
 
+class AreaJavaTest {
   @Test
-  public void name() throws Exception {
-    Area area = new Area(1600).copy(3200);
-    Assert.assertEquals(2, area.getRai());
+  fun name() {
+    val area = Area(1600).copy(3200.0)
+    assertEquals(2, area.rai.toLong())
   }
 }
diff --git a/src/test/kotlin/nectec/thai/unit/AreaTest.kt b/src/test/kotlin/nectec/thai/unit/AreaTest.kt
index 755ecc1..11ac996 100644
--- a/src/test/kotlin/nectec/thai/unit/AreaTest.kt
+++ b/src/test/kotlin/nectec/thai/unit/AreaTest.kt
@@ -18,39 +18,45 @@
 package nectec.thai.unit
 
 import com.google.gson.Gson
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertTrue
 import org.junit.Test
-import kotlin.test.assertEquals
-import kotlin.test.assertTrue
 
 class AreaTest {
 
-  val area = Area(1600.0)
+  private val area = Area(1600.0)
 
-  @Test fun getRai() {
+  @Test
+  fun getRai() {
     assertEquals(1, area.rai)
   }
 
-  @Test fun getNgan() {
+  @Test
+  fun getNgan() {
     assertEquals(0, area.ngan)
   }
 
-  @Test fun getSquareWa() {
-    assertEquals(0.0, area.squareWa)
+  @Test
+  fun getSquareWa() {
+    assertEquals(0.0, area.squareWa, .0)
   }
 
-  @Test fun getSquareMetre() {
-    assertEquals(1600.0, area.squareMetre)
+  @Test
+  fun getSquareMetre() {
+    assertEquals(1600.0, area.squareMetre, .0)
   }
 
-  @Test fun formalPrint() {
-    assertEquals("1 ไร่", area.formalPrint());
-    assertEquals("2 งาน", Area(0, 2, 0).formalPrint());
-    assertEquals("1 ตารางวา", Area(0, 0, 1).formalPrint());
-    assertEquals("1 ไร่ 99 ตารางวา", Area(0, 0, 499).formalPrint());
-    assertEquals("2 ไร่ 3 งาน 99 ตารางวา", Area(0, 7, 499).formalPrint());
+  @Test
+  fun formalPrint() {
+    assertEquals("1 ไร่", area.formalPrint())
+    assertEquals("2 งาน", Area(0, 2, 0).formalPrint())
+    assertEquals("1 ตารางวา", Area(0, 0, 1).formalPrint())
+    assertEquals("1 ไร่ 99 ตารางวา", Area(0, 0, 499).formalPrint())
+    assertEquals("2 ไร่ 3 งาน 99 ตารางวา", Area(0, 7, 499).formalPrint())
   }
 
-  @Test fun prettyPrint() {
+  @Test
+  fun prettyPrint() {
     assertEquals("1-0-0 ไร่", area.prettyPrint())
     assertEquals("0-2-0 ไร่", Area(0, 2, 0).prettyPrint())
     assertEquals("0-0-1.9 ไร่", Area(0, 0, 1.9).prettyPrint())
@@ -58,35 +64,37 @@ class AreaTest {
     assertEquals("2-3-99.75 ไร่", Area(0, 7, 499.75).prettyPrint())
   }
 
-  @Test fun rounding() {
+  @Test
+  fun rounding() {
     val ex1 = Area(2400.0)
     assertEquals(1, ex1.rai)
     assertEquals(2, ex1.ngan)
-    assertEquals(0.0, ex1.squareWa)
+    assertEquals(0.0, ex1.squareWa, .0)
 
     val ex2 = Area(1599.0)
     assertEquals(0, ex2.rai)
     assertEquals(3, ex2.ngan)
-    assertEquals(99.75, ex2.squareWa)
+    assertEquals(99.75, ex2.squareWa, .0)
 
     val ex3 = Area(1605.0)
     assertEquals(1, ex3.rai)
     assertEquals(0, ex3.ngan)
-    assertEquals(1.25, ex3.squareWa)
+    assertEquals(1.25, ex3.squareWa, .0)
 
     val ex4 = Area(1601.0)
     assertEquals(1, ex4.rai)
     assertEquals(0, ex4.ngan)
-    assertEquals(0.25, ex4.squareWa)
+    assertEquals(0.25, ex4.squareWa, .0)
   }
 
-  @Test fun gsonToJson() {
-    assertEquals("{\"rai\":1,\"ngan\":0,\"squareWa\":0.0,\"squareMetre\":1600.0}",
+  @Test
+  fun gsonToJson() {
+    assertEquals("{\"squareMetre\":1600.0,\"rai\":1,\"ngan\":0,\"squareWa\":0.0}",
         Gson().toJson(Area(1600.0)))
-
   }
 
-  @Test fun gsonFromJson() {
+  @Test
+  fun gsonFromJson() {
     val area = Gson().fromJson("{\"rai\":1,\"ngan\":0,\"squareWa\":0,\"squareMetre\":1600}",
         Area::class.java)
     assertEquals(1, area.rai)
@@ -95,7 +103,7 @@ class AreaTest {
   @Test
   fun compare() {
     assertTrue(Area(1, 0, 0) > Area(0, 3, 99))
-    assertTrue(Area(1, 0, 0) == Area(1600.0))
+    assertEquals(Area(1, 0, 0), Area(1600.0))
     assertTrue(Area(2, 0, 0) < Area(4, 0, 99))
   }
 }