org.apache.flink.runtime.state.VoidNamespace Maven / Gradle / Ivy
/*
* 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.state;
import java.io.ObjectStreamException;
/**
* Singleton placeholder class for state without a namespace.
*/
public final class VoidNamespace {
// ------------------------------------------------------------------------
// Singleton instance
// ------------------------------------------------------------------------
/** The singleton instance */
public static final VoidNamespace INSTANCE = new VoidNamespace();
/** Getter for the singleton instance */
public static VoidNamespace get() {
return INSTANCE;
}
/** This class should not be instantiated */
private VoidNamespace() {}
// ------------------------------------------------------------------------
// Standard Utilities
// ------------------------------------------------------------------------
@Override
public int hashCode() {
return 99;
}
@Override
public boolean equals(Object obj) {
return obj == this;
}
@Override
public String toString() {
return getClass().getSimpleName();
}
// ------------------------------------------------------------------------
// Singleton serialization
// ------------------------------------------------------------------------
// make sure that we preserve the singleton properly on serialization
private Object readResolve() throws ObjectStreamException {
return INSTANCE;
}
}