hadoop ConstEnumCounters 源码
haddop ConstEnumCounters 代码
文件路径：/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/util/ConstEnumCounters.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.hadoop.hdfs.util;
/**
* Const Counters for an enum type.
*
* It's the const version of EnumCounters. Any modification ends with a
* ConstEnumException.
*
* @see org.apache.hadoop.hdfs.util.EnumCounters
*/
public class ConstEnumCounters<E extends Enum<E>> extends EnumCounters<E> {
/**
* An exception class for modification on ConstEnumCounters.
*/
public static final class ConstEnumException extends RuntimeException {
private ConstEnumException(String msg) {
super(msg);
}
}
/**
* Throwing this exception if any modification occurs.
*/
private static final ConstEnumException CONST_ENUM_EXCEPTION =
new ConstEnumException("modification on const.");
public ConstEnumCounters(Class<E> enumClass, long defaultVal) {
super(enumClass);
forceReset(defaultVal);
}
@Override
public final void negation() {
throw CONST_ENUM_EXCEPTION;
}
@Override
public final void set(final E e, final long value) {
throw CONST_ENUM_EXCEPTION;
}
@Override
public final void set(final EnumCounters<E> that) {
throw CONST_ENUM_EXCEPTION;
}
@Override
public final void reset() {
throw CONST_ENUM_EXCEPTION;
}
@Override
public final void add(final E e, final long value) {
throw CONST_ENUM_EXCEPTION;
}
@Override
public final void add(final EnumCounters<E> that) {
throw CONST_ENUM_EXCEPTION;
}
@Override
public final void subtract(final E e, final long value) {
throw CONST_ENUM_EXCEPTION;
}
@Override
public final void subtract(final EnumCounters<E> that) {
throw CONST_ENUM_EXCEPTION;
}
@Override
public final void reset(long val) {
throw CONST_ENUM_EXCEPTION;
}
private void forceReset(long val) {
super.reset(val);
}
}
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