Java tutorial
/* * Copyright 2010-2014 Amazon.com, 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. * A copy of the License is located at * * http://aws.amazon.com/apache2.0 * * or in the "license" file accompanying this file. This file 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.github.lpezet.antiope.metrics.aws; import java.util.Comparator; import com.amazonaws.services.cloudwatch.model.Dimension; /** * Used to compare {@link Dimension}. * */ enum DimensionComparator implements Comparator<Dimension> { INSTANCE; /** Used to indicate the two objects being compared are both non-nulls. */ private static final int NON_NULLS = 2; @Override public int compare(Dimension pDim1, Dimension pDim2) { int oResult = nullCompare(pDim1, pDim2); if (oResult == NON_NULLS) { oResult = nullSafeCompare(pDim1.getName(), pDim2.getName()); if (oResult == 0) { return nullSafeCompare(pDim1.getValue(), pDim2.getValue()); } } return oResult; } /** * Compares the two given strings for order, handling null as necessary. * * @return a negative integer, zero, or a positive integer as the first * object is less than, equal to, or greater than the second object. */ private int nullSafeCompare(String pFirst, String pSecond) { int oResult = nullCompare(pFirst, pSecond); return oResult == NON_NULLS ? pFirst.compareTo(pSecond) : oResult; } /** * Partially compares the two given objects for order, handling null as * necessary. * * @return a -1 if the first object is null but not the second, 0 if both * objects are identical, 1 if the second object is null but not the * first. Otherwise, {@link #NON_NULLS} is returned which means both * objects are non-null but not identical. */ private int nullCompare(Object pFirst, Object pSecond) { if (pFirst == pSecond) { return 0; } if (pFirst == null) { return -1; } if (pSecond == null) { return 1; } return NON_NULLS; } }