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/*
 * Copyright 2015, The Querydsl Team (http://www.querydsl.com/team)
 *
 * 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.querydsl.core.group;

import com.querydsl.core.types.Expression;
import java.util.Comparator;
import java.util.LinkedHashSet;
import java.util.Set;
import java.util.SortedSet;
import java.util.TreeSet;

/**
 * GSet
 *
 * @param  t
 * @param  s
 */
public abstract class GSet> extends AbstractGroupExpression {

  private static final long serialVersionUID = -1575808026237160843L;

  public static  GSet> createLinked(Expression expr) {
    return new GSet<>(expr) {
      @Override
      protected Set createSet() {
        return new LinkedHashSet<>();
      }
    };
  }

  public static > GSet> createSorted(
      Expression expr) {
    return new GSet<>(expr) {
      @Override
      protected SortedSet createSet() {
        return new TreeSet<>();
      }
    };
  }

  public static  GSet> createSorted(
      Expression expr, final Comparator comparator) {
    return new GSet<>(expr) {
      @Override
      protected SortedSet createSet() {
        return new TreeSet<>(comparator);
      }
    };
  }

  GSet(Expression expr) {
    super(Set.class, expr);
  }

  protected abstract S createSet();

  @Override
  public GroupCollector createGroupCollector() {
    return new GroupCollector<>() {

      private final S set = createSet();

      @Override
      public void add(T o) {
        if (o != null) {
          set.add(o);
        }
      }

      @Override
      public S get() {
        return set;
      }
    };
  }
}