flink-runtime/src/main/java/org/apache/flink/runtime/persistence/StringResourceVersion.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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 org.apache.flink.runtime.persistence;

import org.apache.flink.util.Preconditions;

import javax.annotation.Nonnull;

import java.util.Objects;

/**
 * {@link ResourceVersion} implementation with {@link String} value. The resource version in
 * Kubernetes is {@link String}. And they have same length, we could easily compare string.
 */
public class StringResourceVersion implements ResourceVersion<StringResourceVersion> {

    private static final long serialVersionUID = 1L;

    private static final StringResourceVersion NOT_EXISTING = new StringResourceVersion("-1");

    private final String value;

    private StringResourceVersion(String value) {
        this.value = value;
    }

    @Override
    public int compareTo(@Nonnull StringResourceVersion other) {
        return this.value.compareTo(other.value);
    }

    @Override
    public boolean equals(Object obj) {
        if (obj == this) {
            return true;
        } else if (obj != null && obj.getClass() == StringResourceVersion.class) {
            final StringResourceVersion that = (StringResourceVersion) obj;
            return Objects.equals(this.value, that.value);
        } else {
            return false;
        }
    }

    @Override
    public int hashCode() {
        return Objects.hashCode(value);
    }

    @Override
    public boolean isExisting() {
        return this != NOT_EXISTING;
    }

    @Override
    public String toString() {
        return "StringResourceVersion{" + "value='" + value + '\'' + '}';
    }

    public String getValue() {
        return this.value;
    }

    public static StringResourceVersion notExisting() {
        return NOT_EXISTING;
    }

    public static StringResourceVersion valueOf(String value) {
        Preconditions.checkArgument(!value.equals(NOT_EXISTING.getValue()));
        return new StringResourceVersion(value);
    }
}