/*
* Copyright (C) 2014 Google, Inc.
*
* 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 dagger.internal;
import java.util.LinkedHashMap;
import java.util.LinkedHashSet;
final class Collections {
/**
* The maximum value for a signed 32-bit integer that is equal to a power of 2.
*/
private static final int MAX_POWER_OF_TWO = 1 << (Integer.SIZE - 2);
private Collections() {
}
/**
* Creates a {@link LinkedHashSet} instance, with a high enough "initial capacity" that it
* should hold {@code expectedSize} elements without growth.
*/
static LinkedHashSet newLinkedHashSetWithExpectedSize(int expectedSize) {
return new LinkedHashSet(calculateInitialCapacity(expectedSize));
}
/**
* Creates a {@link LinkedHashMap} instance, with a high enough "initial capacity" that it
* should hold {@code expectedSize} elements without growth.
*/
static LinkedHashMap newLinkedHashMapWithExpectedSize(int expectedSize) {
return new LinkedHashMap(calculateInitialCapacity(expectedSize));
}
private static int calculateInitialCapacity(int expectedSize) {
if (expectedSize < 3) {
return expectedSize + 1;
}
if (expectedSize < MAX_POWER_OF_TWO) {
// This is the calculation used in JDK8 to resize when a putAll
// happens; it seems to be the most conservative calculation we
// can make. 0.75 is the default load factor.
return (int) (expectedSize / 0.75F + 1.0F);
}
return Integer.MAX_VALUE; // any large value
}
}