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Posted to dev@commons.apache.org by sc...@apache.org on 2003/09/26 00:47:49 UTC

cvs commit: jakarta-commons/collections/src/java/org/apache/commons/collections/pairs KeyValuePair.java AbstractMapEntry.java AbstractPair.java Pair.java DefaultMapEntry.java

scolebourne    2003/09/25 15:47:49

  Added:       collections/src/java/org/apache/commons/collections/pairs
                        KeyValuePair.java AbstractMapEntry.java
                        AbstractPair.java Pair.java DefaultMapEntry.java
  Log:
  New Pair implementations
  
  Revision  Changes    Path
  1.1                  jakarta-commons/collections/src/java/org/apache/commons/collections/pairs/KeyValuePair.java
  
  Index: KeyValuePair.java
  ===================================================================
  /*
   * $Header: /home/cvs/jakarta-commons/collections/src/java/org/apache/commons/collections/pairs/KeyValuePair.java,v 1.1 2003/09/25 22:47:49 scolebourne Exp $
   * ====================================================================
   *
   * The Apache Software License, Version 1.1
   *
   * Copyright (c) 2001-2003 The Apache Software Foundation.  All rights
   * reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   *
   * 1. Redistributions of source code must retain the above copyright
   *    notice, this list of conditions and the following disclaimer.
   *
   * 2. Redistributions in binary form must reproduce the above copyright
   *    notice, this list of conditions and the following disclaimer in
   *    the documentation and/or other materials provided with the
   *    distribution.
   *
   * 3. The end-user documentation included with the redistribution, if
   *    any, must include the following acknowledgement:
   *       "This product includes software developed by the
   *        Apache Software Foundation (http://www.apache.org/)."
   *    Alternately, this acknowledgement may appear in the software itself,
   *    if and wherever such third-party acknowledgements normally appear.
   *
   * 4. The names "The Jakarta Project", "Commons", and "Apache Software
   *    Foundation" must not be used to endorse or promote products derived
   *    from this software without prior written permission. For written
   *    permission, please contact apache@apache.org.
   *
   * 5. Products derived from this software may not be called "Apache"
   *    nor may "Apache" appear in their names without prior written
   *    permission of the Apache Software Foundation.
   *
   * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
   * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
   * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
   * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
   * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
   * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
   * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
   * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
   * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
   * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   * SUCH DAMAGE.
   * ====================================================================
   *
   * This software consists of voluntary contributions made by many
   * individuals on behalf of the Apache Software Foundation.  For more
   * information on the Apache Software Foundation, please see
   * <http://www.apache.org/>.
   *
   */
  package org.apache.commons.collections.pairs;
  
  import java.util.Map;
  
  /**
   * A mutable key-value pair that does not implement Map Entry.
   * <p>
   * Note that a <code>KeyValuePair</code> instance may not contain
   * itself as a key or value.
   *
   * @since Commons Collections 3.0
   * @version $Revision: 1.1 $ $Date: 2003/09/25 22:47:49 $
   * 
   * @author James Strachan
   * @author Michael A. Smith
   * @author Neil O'Toole
   * @author Stephen Colebourne
   */
  public class KeyValuePair extends AbstractPair {
  
      /**
       * Constructs a new pair with a null key and null value.
       */
      public KeyValuePair() {
          super(null, null);
      }
  
      /**
       * Constructs a new pair with the specified key and given value.
       *
       * @param key  the key for the entry, may be null
       * @param value  the value for the entry, may be null
       */
      public KeyValuePair(final Object key, final Object value) {
          super(key, value);
      }
  
      /**
       * Constructs a new pair from the specified Pair.
       *
       * @param pair  the pair to copy, must not be null
       * @throws NullPointerException if the entry is null
       */
      public KeyValuePair(final Pair pair) {
          super(pair.getKey(), pair.getValue());
      }
  
      /**
       * Constructs a new pair from the specified Map Entry.
       *
       * @param entry  the entry to copy, must not be null
       * @throws NullPointerException if the entry is null
       */
      public KeyValuePair(final Map.Entry entry) {
          super(entry.getKey(), entry.getValue());
      }
  
      //-----------------------------------------------------------------------
      /**
       * Sets the key.
       *
       * @param key  the new key
       * @return the old key
       * @throws IllegalArgumentException if key is this object
       */
      public Object setKey(final Object key) {
          if (key == this) {
              throw new IllegalArgumentException("A KeyValuePair may not contain itself as a key.");
          }
  
          final Object old = this.key;
          this.key = key;
          return old;
      }
  
      /** 
       * Sets the value.
       *
       * @return the old value of the value
       * @param value the new value
       * @throws IllegalArgumentException if value is this object
       */
      public Object setValue(final Object value) {
          if (value == this) {
              throw new IllegalArgumentException("A KeyValuePair may not contain itself as a value.");
          }
  
          final Object old = this.value;
          this.value = value;
          return old;
      }
  
      //-----------------------------------------------------------------------
      /**
       * Returns a new <code>Map.Entry</code> object with key and value from this <code>KeyValuePair</code>.
       */
      public Map.Entry toMapEntry() {
          return new DefaultMapEntry(this.getKey(), this.getValue());
      }
  
      //-----------------------------------------------------------------------
      /**
       * Compares this Map Entry with another Map Entry.
       * <p>
       * Returns true if the compared object is also a <code>KeyValuePair</code>,
       * and its key and value are equal to this object's key and value.
       * 
       * @param obj  the object to compare to
       * @return true if equal key and value
       */
      public boolean equals(final Object obj) {
          if (obj == this) {
              return true;
          }
          if (obj instanceof KeyValuePair == false) {
              return false;
          }
  
          KeyValuePair other = (KeyValuePair) obj;
          return 
              (getKey() == null ? other.getKey() == null : getKey().equals(other.getKey())) &&
              (getValue() == null ? other.getValue() == null : getValue().equals(other.getValue()));
      }
  
      /**
       * Gets a hashCode compatible with the equals method.
       * <p>
       * Implemented per API documentation of {@link java.util.Map.Entry#hashCode()},
       * however subclasses may override this.
       * 
       * @return a suitable hashcode
       */
      public int hashCode() {
          return (getKey() == null ? 0 : getKey().hashCode()) ^
                 (getValue() == null ? 0 : getValue().hashCode());
      }
  
  }
  
  
  
  1.1                  jakarta-commons/collections/src/java/org/apache/commons/collections/pairs/AbstractMapEntry.java
  
  Index: AbstractMapEntry.java
  ===================================================================
  /*
   * $Header: /home/cvs/jakarta-commons/collections/src/java/org/apache/commons/collections/pairs/AbstractMapEntry.java,v 1.1 2003/09/25 22:47:49 scolebourne Exp $
   * ====================================================================
   *
   * The Apache Software License, Version 1.1
   *
   * Copyright (c) 2001-2003 The Apache Software Foundation.  All rights
   * reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   *
   * 1. Redistributions of source code must retain the above copyright
   *    notice, this list of conditions and the following disclaimer.
   *
   * 2. Redistributions in binary form must reproduce the above copyright
   *    notice, this list of conditions and the following disclaimer in
   *    the documentation and/or other materials provided with the
   *    distribution.
   *
   * 3. The end-user documentation included with the redistribution, if
   *    any, must include the following acknowledgement:
   *       "This product includes software developed by the
   *        Apache Software Foundation (http://www.apache.org/)."
   *    Alternately, this acknowledgement may appear in the software itself,
   *    if and wherever such third-party acknowledgements normally appear.
   *
   * 4. The names "The Jakarta Project", "Commons", and "Apache Software
   *    Foundation" must not be used to endorse or promote products derived
   *    from this software without prior written permission. For written
   *    permission, please contact apache@apache.org.
   *
   * 5. Products derived from this software may not be called "Apache"
   *    nor may "Apache" appear in their names without prior written
   *    permission of the Apache Software Foundation.
   *
   * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
   * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
   * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
   * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
   * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
   * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
   * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
   * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
   * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
   * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   * SUCH DAMAGE.
   * ====================================================================
   *
   * This software consists of voluntary contributions made by many
   * individuals on behalf of the Apache Software Foundation.  For more
   * information on the Apache Software Foundation, please see
   * <http://www.apache.org/>.
   *
   */
  package org.apache.commons.collections.pairs;
  
  import java.util.Map;
  
  /**
   * Abstract Pair class to assist with creating correct Map Entry implementations.
   *
   * @since Commons Collections 3.0
   * @version $Revision: 1.1 $ $Date: 2003/09/25 22:47:49 $
   * 
   * @author James Strachan
   * @author Michael A. Smith
   * @author Neil O'Toole
   * @author Stephen Colebourne
   */
  public class AbstractMapEntry extends AbstractPair implements Map.Entry {
      
      /**
       * Constructs a new entry with the given key and given value.
       *
       * @param key  the key for the entry, may be null
       * @param value  the value for the entry, may be null
       */
      protected AbstractMapEntry(Object key, Object value) {
          super(key, value);
      }
  
      // Map.Entry interface
      //-------------------------------------------------------------------------
      /** 
       * Sets the value stored in this Map Entry.
       * <p>
       * This Map Entry is not connected to a Map, so only the local data is changed.
       *
       * @param value  the new value
       * @return the previous value
       */
      public Object setValue(Object value) {
          Object answer = this.value;
          this.value = value;
          return answer;
      }
  
      /**
       * Compares this Map Entry with another Map Entry.
       * <p>
       * Implemented per API documentation of {@link java.util.Map.Entry#equals(Object)}
       * 
       * @param obj  the object to compare to
       * @return true if equal key and value
       */
      public boolean equals(Object obj) {
          if (obj == this) {
              return true;
          }
          if (obj instanceof Map.Entry == false) {
              return false;
          }
          Map.Entry other = (Map.Entry) obj;
          return
              (getKey() == null ? other.getKey() == null : getKey().equals(other.getKey())) &&
              (getValue() == null ? other.getValue() == null : getValue().equals(other.getValue()));
      }
       
      /**
       * Gets a hashCode compatible with the equals method.
       * <p>
       * Implemented per API documentation of {@link java.util.Map.Entry#hashCode()}
       * 
       * @return a suitable hashcode
       */
      public int hashCode() {
          return (getKey() == null ? 0 : getKey().hashCode()) ^
                 (getValue() == null ? 0 : getValue().hashCode()); 
      }
  
  }
  
  
  
  1.1                  jakarta-commons/collections/src/java/org/apache/commons/collections/pairs/AbstractPair.java
  
  Index: AbstractPair.java
  ===================================================================
  /*
   * $Header: /home/cvs/jakarta-commons/collections/src/java/org/apache/commons/collections/pairs/AbstractPair.java,v 1.1 2003/09/25 22:47:49 scolebourne Exp $
   * ====================================================================
   *
   * The Apache Software License, Version 1.1
   *
   * Copyright (c) 2001-2003 The Apache Software Foundation.  All rights
   * reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   *
   * 1. Redistributions of source code must retain the above copyright
   *    notice, this list of conditions and the following disclaimer.
   *
   * 2. Redistributions in binary form must reproduce the above copyright
   *    notice, this list of conditions and the following disclaimer in
   *    the documentation and/or other materials provided with the
   *    distribution.
   *
   * 3. The end-user documentation included with the redistribution, if
   *    any, must include the following acknowledgement:
   *       "This product includes software developed by the
   *        Apache Software Foundation (http://www.apache.org/)."
   *    Alternately, this acknowledgement may appear in the software itself,
   *    if and wherever such third-party acknowledgements normally appear.
   *
   * 4. The names "The Jakarta Project", "Commons", and "Apache Software
   *    Foundation" must not be used to endorse or promote products derived
   *    from this software without prior written permission. For written
   *    permission, please contact apache@apache.org.
   *
   * 5. Products derived from this software may not be called "Apache"
   *    nor may "Apache" appear in their names without prior written
   *    permission of the Apache Software Foundation.
   *
   * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
   * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
   * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
   * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
   * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
   * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
   * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
   * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
   * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
   * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   * SUCH DAMAGE.
   * ====================================================================
   *
   * This software consists of voluntary contributions made by many
   * individuals on behalf of the Apache Software Foundation.  For more
   * information on the Apache Software Foundation, please see
   * <http://www.apache.org/>.
   *
   */
  package org.apache.commons.collections.pairs;
  
  /**
   * Abstract Pair class to assist with creating Pair and Map Entry implementations.
   *
   * @since Commons Collections 3.0
   * @version $Revision: 1.1 $ $Date: 2003/09/25 22:47:49 $
   * 
   * @author James Strachan
   * @author Michael A. Smith
   * @author Neil O'Toole
   * @author Stephen Colebourne
   */
  public abstract class AbstractPair {
      
      /** The key */
      protected Object key;
      /** The value */
      protected Object value;
      
      /**
       * Constructs a new pair with the specified key and given value.
       *
       * @param key  the key for the entry, may be null
       * @param value  the value for the entry, may be null
       */
      protected AbstractPair(Object key, Object value) {
          super();
          this.key = key;
          this.value = value;
      }
  
      /**
       * Gets the key from the pair.
       *
       * @return the key 
       */
      public Object getKey() {
          return key;
      }
  
      /**
       * Gets the value from the pair.
       *
       * @return the value
       */
      public Object getValue() {
          return value;
      }
  
      /**
       * Gets a debugging String view of the pair.
       * 
       * @return a String view of the entry
       */
      public String toString() {
          return new StringBuffer()
              .append('[')
              .append(getKey())
              .append('=')
              .append(getValue())
              .append(']').toString();
      }
  
  }
  
  
  
  1.1                  jakarta-commons/collections/src/java/org/apache/commons/collections/pairs/Pair.java
  
  Index: Pair.java
  ===================================================================
  /*
   * $Header: /home/cvs/jakarta-commons/collections/src/java/org/apache/commons/collections/pairs/Pair.java,v 1.1 2003/09/25 22:47:49 scolebourne Exp $
   * ====================================================================
   *
   * The Apache Software License, Version 1.1
   *
   * Copyright (c) 2001-2003 The Apache Software Foundation.  All rights
   * reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   *
   * 1. Redistributions of source code must retain the above copyright
   *    notice, this list of conditions and the following disclaimer.
   *
   * 2. Redistributions in binary form must reproduce the above copyright
   *    notice, this list of conditions and the following disclaimer in
   *    the documentation and/or other materials provided with the
   *    distribution.
   *
   * 3. The end-user documentation included with the redistribution, if
   *    any, must include the following acknowledgement:
   *       "This product includes software developed by the
   *        Apache Software Foundation (http://www.apache.org/)."
   *    Alternately, this acknowledgement may appear in the software itself,
   *    if and wherever such third-party acknowledgements normally appear.
   *
   * 4. The names "The Jakarta Project", "Commons", and "Apache Software
   *    Foundation" must not be used to endorse or promote products derived
   *    from this software without prior written permission. For written
   *    permission, please contact apache@apache.org.
   *
   * 5. Products derived from this software may not be called "Apache"
   *    nor may "Apache" appear in their names without prior written
   *    permission of the Apache Software Foundation.
   *
   * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
   * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
   * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
   * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
   * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
   * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
   * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
   * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
   * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
   * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   * SUCH DAMAGE.
   * ====================================================================
   *
   * This software consists of voluntary contributions made by many
   * individuals on behalf of the Apache Software Foundation.  For more
   * information on the Apache Software Foundation, please see
   * <http://www.apache.org/>.
   *
   */
  package org.apache.commons.collections.pairs;
  
  /**
   * Defines a simple key value Pair.
   *
   * @since Commons Collections 3.0
   * @version $Revision: 1.1 $ $Date: 2003/09/25 22:47:49 $
   * 
   * @author Stephen Colebourne
   */
  public interface Pair {
      
      /**
       * Gets the key from the pair.
       *
       * @return the key 
       */
      Object getKey();
  
      /**
       * Gets the value from the pair.
       *
       * @return the value
       */
      Object getValue();
  
  }
  
  
  
  1.1                  jakarta-commons/collections/src/java/org/apache/commons/collections/pairs/DefaultMapEntry.java
  
  Index: DefaultMapEntry.java
  ===================================================================
  /*
   * $Header: /home/cvs/jakarta-commons/collections/src/java/org/apache/commons/collections/pairs/DefaultMapEntry.java,v 1.1 2003/09/25 22:47:49 scolebourne Exp $
   * ====================================================================
   *
   * The Apache Software License, Version 1.1
   *
   * Copyright (c) 2001-2003 The Apache Software Foundation.  All rights
   * reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   *
   * 1. Redistributions of source code must retain the above copyright
   *    notice, this list of conditions and the following disclaimer.
   *
   * 2. Redistributions in binary form must reproduce the above copyright
   *    notice, this list of conditions and the following disclaimer in
   *    the documentation and/or other materials provided with the
   *    distribution.
   *
   * 3. The end-user documentation included with the redistribution, if
   *    any, must include the following acknowledgement:
   *       "This product includes software developed by the
   *        Apache Software Foundation (http://www.apache.org/)."
   *    Alternately, this acknowledgement may appear in the software itself,
   *    if and wherever such third-party acknowledgements normally appear.
   *
   * 4. The names "The Jakarta Project", "Commons", and "Apache Software
   *    Foundation" must not be used to endorse or promote products derived
   *    from this software without prior written permission. For written
   *    permission, please contact apache@apache.org.
   *
   * 5. Products derived from this software may not be called "Apache"
   *    nor may "Apache" appear in their names without prior written
   *    permission of the Apache Software Foundation.
   *
   * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
   * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
   * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
   * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
   * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
   * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
   * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
   * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
   * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
   * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   * SUCH DAMAGE.
   * ====================================================================
   *
   * This software consists of voluntary contributions made by many
   * individuals on behalf of the Apache Software Foundation.  For more
   * information on the Apache Software Foundation, please see
   * <http://www.apache.org/>.
   *
   */
  package org.apache.commons.collections.pairs;
  
  import java.util.Map;
  
  /**
   * A restricted implementation of {@link java.util.Map.Entry} that prevents
   * the Map Entry contract from being broken.
   *
   * @since Commons Collections 3.0
   * @version $Revision: 1.1 $ $Date: 2003/09/25 22:47:49 $
   * 
   * @author James Strachan
   * @author Michael A. Smith
   * @author Neil O'Toole
   * @author Stephen Colebourne
   */
  public final class DefaultMapEntry extends AbstractMapEntry {
      
      /**
       * Constructs a new entry with the specified key and given value.
       *
       * @param key  the key for the entry, may be null
       * @param value  the value for the entry, may be null
       */
      public DefaultMapEntry(final Object key, final Object value) {
          super(key, value);
      }
  
      /**
       * Constructs a new entry from the specified Pair.
       *
       * @param pair  the pair to copy, must not be null
       * @throws NullPointerException if the entry is null
       */
      public DefaultMapEntry(final Pair pair) {
          super(pair.getKey(), pair.getValue());
      }
  
      /**
       * Constructs a new entry from the specified Map Entry.
       *
       * @param entry  the entry to copy, must not be null
       * @throws NullPointerException if the entry is null
       */
      public DefaultMapEntry(final Map.Entry entry) {
          super(entry.getKey(), entry.getValue());
      }
  
  }