/**
* 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.hadoop.util;
/**
* Sequential number generator. Synchronized on method since we only have one variable
* per instance. May need to consider other ways if we are going to add more variables to
* this class.
*
* This class is thread safe.
*/
public abstract class SequentialNumber {
private long currentValue;
/** Create a new instance with the given initial value. */
protected SequentialNumber(final long initialValue) {
currentValue = initialValue;
}
/** @return the current value. */
public synchronized long getCurrentValue() {
return currentValue;
}
/** Set current value. */
public synchronized void setCurrentValue(final long value) {
currentValue = value;
}
/** Increment and then return the next value. */
public synchronized long nextValue() {
return ++currentValue;
}
/** Skip to the new value. */
public synchronized void skipTo(final long newValue) throws IllegalStateException {
if (newValue < currentValue) {
throw new IllegalStateException(
"Cannot skip to less than the current value (="
+ currentValue + "), where newValue=" + newValue);
}
currentValue = newValue;
}
@Override
public boolean equals(final Object that) {
if (that == null || this.getClass() != that.getClass()) {
return false;
}
final long thatValue = ((SequentialNumber)that).currentValue;
return currentValue == thatValue;
}
@Override
public int hashCode() {
return (int)currentValue ^ (int)(currentValue >>> 32);
}
}