A Comparator for Boolean objects that can sort either true or false first

   
/*
 * Copyright 2002-2005 the original author or authors.
 *
 * 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.
 */


import java.io.Serializable;
import java.util.Comparator;

/**
 * A Comparator for Boolean objects that can sort either true or false first.
 *
 * @author Keith Donald
 * @since 1.2.2
 */
public final class BooleanComparator implements Comparator, Serializable {

  /**
   * A shared default instance of this comparator, treating true lower
   * than false.
   */
  public static final BooleanComparator TRUE_LOW = new BooleanComparator(true);

  /**
   * A shared default instance of this comparator, treating true higher
   * than false.
   */
  public static final BooleanComparator TRUE_HIGH = new BooleanComparator(false);


  private final boolean trueLow;


  /**
   * Create a BooleanComparator that sorts boolean values based on
   * the provided flag.
   * <p>Alternatively, you can use the default shared instances:
   * <code>BooleanComparator.TRUE_LOW</code> and
   * <code>BooleanComparator.TRUE_HIGH</code>.
   * @param trueLow whether to treat true as lower or higher than false
   * @see #TRUE_LOW
   * @see #TRUE_HIGH
   */
  public BooleanComparator(boolean trueLow) {
    this.trueLow = trueLow;
  }


  public int compare(Object o1, Object o2) {
    boolean v1 = ((Boolean) o1).booleanValue();
    boolean v2 = ((Boolean) o2).booleanValue();
    return (v1 ^ v2) ? ((v1 ^ this.trueLow) ? 1 : -1) : 0;
  }

  public boolean equals(Object obj) {
    if (this == obj) {
      return true;
    }
    if (!(obj instanceof BooleanComparator)) {
      return false;
    }
    return (this.trueLow == ((BooleanComparator) obj).trueLow);
  }

  public int hashCode() {
    return (this.trueLow ? -1 : 1) * getClass().hashCode();
  }

  public String toString() {
    return "BooleanComparator: " + (this.trueLow ? "true low" : "true high");
  }

}

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A Comparator for Boolean objects that can sort either true or false first : Comparator « Collections Data Structure « Java

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