build: use gradle instead of maven

remove checkstyle

BREAKING CHANGE: minimum java version bumped from 6 to 8

Closes #20

build.gradle

@@ -0,0 +1,57 @@
+plugins {
+    id 'java-library'
+    id 'maven-publish'
+    id 'com.github.ben-manes.versions' version '0.28.0'
+    id 'com.autonomousapps.dependency-analysis' version '0.52.0'
+    id 'dev.jacomet.logging-capabilities' version '0.9.0'
+}
+
+repositories {
+    mavenCentral()
+//    maven {
+//        url = uri('https://oss.sonatype.org/content/repositories/snapshots')
+//    }
+//
+//    maven {
+//        url = uri('http://repo.maven.apache.org/maven2')
+//    }
+}
+
+dependencies {
+    implementation 'commons-logging:commons-logging:1.2'
+    api 'org.apache.commons:commons-vfs2:2.2'
+
+    testImplementation 'junit:junit:4.12'
+    testImplementation 'commons-io:commons-io:1.3.2'
+    testImplementation 'org.mockito:mockito-core:2.23.4'
+    testImplementation 'org.assertj:assertj-core:3.16.1'
+}
+
+group = 'com.github.junrar'
+version = '4.0.1-SNAPSHOT'
+description = 'rar decompression library in plain java'
+
+
+sourceCompatibility = '1.8'
+targetCompatibility = '1.8'
+
+java {
+    withSourcesJar()
+}
+
+//publishing {
+//    publications {
+//        maven(MavenPublication) {
+//            from(components.java)
+//        }
+//    }
+//}
+
+tasks.withType(JavaCompile) {
+    options.encoding = 'UTF-8'
+}
+
+tasks.wrapper {
+    gradleVersion = '6.5.1'
+    distributionType = Wrapper.DistributionType.ALL
+}

gradle/wrapper/gradle-wrapper.properties

@@ -0,0 +1,6 @@
+#Thu Jul 16 16:23:36 HKT 2020
+distributionUrl=https\://services.gradle.org/distributions/gradle-6.5.1-all.zip
+distributionBase=GRADLE_USER_HOME
+distributionPath=wrapper/dists
+zipStorePath=wrapper/dists
+zipStoreBase=GRADLE_USER_HOME