Java tutorial
/** * Copyright (C) 2017 Marvin Herman Froeder (velobr@gmail.com) * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package com.marvinformatics.manifestvalidatorplugin.oo; import java.util.Optional; import java.util.jar.JarFile; import com.google.common.base.Strings; public class AbsentRule implements ManifestRule { @Override public Optional<String> validate(String value, JarFile jar) { if (Strings.isNullOrEmpty(value)) return Optional.of("Expected to be absent"); return Optional.empty(); } }