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/*
* Copyright 2008 Amazon Technologies, Inc. or its affiliates.
* Amazon, Amazon.com and Carbonado are trademarks or registered trademarks
* of Amazon Technologies, Inc. or its affiliates. All rights reserved.
*
* Licensed 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 com.amazon.carbonado.qe;
import java.util.EnumMap;
/**
* An immutable map of query hints.
*
* @author Brian S O'Neill
* @see QueryHint
* @since 1.2
*/
public class QueryHints implements java.io.Serializable {
private static final long serialVersionUID = 1L;
private static final QueryHints EMPTY_HINTS = new QueryHints(null);
public static QueryHints emptyHints() {
return EMPTY_HINTS;
}
private final EnumMap<QueryHint, Object> mMap;
private QueryHints(EnumMap<QueryHint, Object> map) {
mMap = map;
}
/**
* Returns a new QueryHints object with the given hint. The associated
* value is the hint object itself.
*
* @throws IllegalArgumentException if hint is null
*/
public QueryHints with(QueryHint hint) {
return with(hint, hint);
}
/**
* Returns a new QueryHints object with the given hint and value.
*
* @throws IllegalArgumentException if hint or value is null
*/
public QueryHints with(QueryHint hint, Object value) {
if (hint == null) {
throw new IllegalArgumentException("Null hint");
}
if (value == null) {
throw new IllegalArgumentException("Null value");
}
EnumMap<QueryHint, Object> map;
if (mMap == null) {
map = new EnumMap<QueryHint, Object>(QueryHint.class);
} else {
map = mMap.clone();
}
map.put(hint, value);
return new QueryHints(map);
}
/**
* Returns a new QueryHints object without the given hint.
*/
public QueryHints without(QueryHint hint) {
if (hint == null || mMap == null || !mMap.containsKey(hint)) {
return this;
}
EnumMap<QueryHint, Object> map = mMap.clone();
map.remove(hint);
if (map.size() == 0) {
map = null;
}
return new QueryHints(map);
}
/**
* Returns false if hint is not provided.
*/
public boolean contains(QueryHint hint) {
return get(hint) != null;
}
/**
* Returns null if hint is not provided.
*/
public Object get(QueryHint hint) {
return hint == null ? null : (mMap == null ? null : mMap.get(hint));
}
public boolean isEmpty() {
return mMap == null ? true : mMap.isEmpty();
}
@Override
public int hashCode() {
return mMap == null ? 0 : mMap.hashCode();
}
@Override
public boolean equals(Object obj) {
if (this == obj) {
return true;
}
if (obj instanceof QueryHints) {
QueryHints other = (QueryHints) obj;
if (mMap == null) {
return other.mMap == null;
} else {
return mMap.equals(other.mMap);
}
}
return false;
}
@Override
public String toString() {
if (mMap == null) {
return "QueryHints: {}";
}
return "QueryHints: " + mMap;
}
}
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