AccountInfoComparator.java example

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// Copyright (C) 2015 The Android Open Source Project
//
// 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.google.gerrit.server.api.accounts;

import com.google.common.collect.ComparisonChain;
import com.google.common.collect.Ordering;
import com.google.gerrit.extensions.common.AccountInfo;
import java.util.Comparator;

public class AccountInfoComparator extends Ordering<AccountInfo>
    implements Comparator<AccountInfo> {
  public static final AccountInfoComparator ORDER_NULLS_FIRST = new AccountInfoComparator();
  public static final AccountInfoComparator ORDER_NULLS_LAST =
      new AccountInfoComparator().setNullsLast();

  private boolean nullsLast;

  private AccountInfoComparator() {}

  private AccountInfoComparator setNullsLast() {
    this.nullsLast = true;
    return this;
  }

  @Override
  public int compare(AccountInfo a, AccountInfo b) {
    return ComparisonChain.start()
        .compare(a.name, b.name, createOrdering())
        .compare(a.email, b.email, createOrdering())
        .compare(a._accountId, b._accountId, createOrdering())
        .result();
  }

  private <S extends Comparable<?>> Ordering<S> createOrdering() {
    if (nullsLast) {
      return Ordering.natural().nullsLast();
    }
    return Ordering.natural().nullsFirst();
  }
}