// =================================================================================================
// Copyright 2011 Twitter, Inc.
// -------------------------------------------------------------------------------------------------
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this work except in compliance with the License.
// You may obtain a copy of the License in the LICENSE file, or 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.twitter.common.stats;
/**
* A convenience class to perform the basic tasks needed for a {@link RecordingStat} except the
* actual value calculation.
*
* @author William Farner
*/
public abstract class SampledStat<T extends Number> extends StatImpl<T> implements RecordingStat<T> {
private volatile T prevValue;
public SampledStat(String name, T defaultValue) {
super(name);
this.prevValue = defaultValue; /* Don't forbid null. */
}
public abstract T doSample();
@Override
public final T sample() {
prevValue = doSample();
return prevValue;
}
@Override
public T read() {
return prevValue;
}
}