Added gradle build system

build.gradle

@@ -0,0 +1,56 @@
+apply plugin: 'java'
+apply plugin: 'checkstyle'
+
+dependencies {
+    compile fileTree(include: ['*.jar'], dir:'lib')
+    testCompile fileTree(include: ['*.jar'], dir:'lib')
+    testImplementation fileTree(include: ['*.jar'], dir:'lib')
+    testRuntime fileTree(include: ['*.jar'], dir:'lib')
+	checkstyle files('lib/checkstyle-8.20-all.jar')
+}
+
+checkstyle {
+    toolVersion '8.20'
+	configFile file('checkstyle.xml')
+}
+
+sourceSets {
+	main {
+		java {
+			srcDir 'src/main'
+		}
+	}
+	test {
+		java {
+			srcDir 'src/test'
+		}
+	}
+}
+test {
+    useJUnitPlatform()
+    testLogging {
+        showStandardStreams = true
+    }
+}
+
+task run(type: JavaExec) {
+  group = 'Run'
+  description = 'Run main'
+
+  classpath sourceSets.main.runtimeClasspath
+  main = "ui"
+  //args "arg1", "arg2"
+}
+
+task tags(type: Exec) {
+  description = 'Update tags file'
+  
+  commandLine 'ctags', '-R', 'src'
+}
+
+checkstyleMain {
+    source ='src/main'
+}
+checkstyleTest {
+    source ='src/test'
+}