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JavaUtil is a utility library to speed the development of
Java software. We developed it over multiple years during
our internal development efforts, and it has reached a
point of stability where we have decided to make it
available to the outside world. The JavaUtil package aims
to fill in the gaps of the Apache Commons and similar
utility libraries out there. Features include convenience
classes for string, collections, arrays, dates, iterators,
colors, logging, unit testing, a little bit of basic
statistics, database queries, caching and more.
package org.arp.javautil.collections;
/*-
* #%L
* JavaUtil
* %%
* Copyright (C) 2012 - 2017 Emory University
* %%
* 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.
* #L%
*/
import java.util.HashMap;
/**
*
* @author Andrew Post
*/
public class HashMapFactory {
public HashMap getInstance(int expectedSize) {
return new HashMap<>(hashMapCapacity(expectedSize));
}
private static int hashMapCapacity(int expectedSize) {
if (expectedSize < 0) {
throw new IllegalArgumentException("expectedSize cannot be < 0");
}
if (expectedSize < 3) {
return expectedSize + 1;
} else if (expectedSize < 1 << (Integer.SIZE - 2)) { //largest power of two
return expectedSize + expectedSize / 3;
} else {
return Integer.MAX_VALUE;
}
}
}