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== Conversion of different Collection data types ==

Implementations of the Collection interface normally have a constructor that accepts a Collection object.
This enables you to convert a Collection to a different type of Collection, such as a Queue to a List, or a List to a Set, etc. Here are the constructors of some implementations:



<source lang="java">
public ArrayList (Collection c)
public HashSet (Collection c)
public LinkedList (Collection c)</source>



<pre class=codeResult>[World, Hello]</pre>

== Deep clone collection: Returns a new collection containing clones of all the items in the specified collection. ==



<source lang="java">
/*
* JCommon : a free general purpose class library for the Java(tm) platform
*
*
* (C) Copyright 2000-2008, by Object Refinery Limited and Contributors.
*
* Project Info: http://www.jfree.org/jcommon/index.html
*
* This library is free software; you can redistribute it and/or modify it
* under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation; either version 2.1 of the License, or
* (at your option) any later version.
*
* This library is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
* License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
* USA.
*
* [Java is a trademark or registered trademark of Sun Microsystems, Inc.
* in the United States and other countries.]
*
* -------------------
* ShapeUtilities.java
* -------------------
* (C)opyright 2003-2008, by Object Refinery Limited and Contributors.
*
* Original Author: David Gilbert (for Object Refinery Limited);
* Contributor(s): -;
*
* $Id: ShapeUtilities.java,v 1.18 2008/06/02 06:58:28 mungady Exp $
*
* Changes
* -------
* 13-Aug-2003 : Version 1 (DG);
* 16-Mar-2004 : Moved rotateShape() from RefineryUtilities.java to here (DG);
* 13-May-2004 : Added new shape creation methods (DG);
* 30-Sep-2004 : Added createLineRegion() method (DG);
* Moved drawRotatedShape() method from RefineryUtilities class
* to this class (DG);
* 04-Oct-2004 : Renamed ShapeUtils --> ShapeUtilities (DG);
* 26-Oct-2004 : Added a method to test the equality of two Line2D
* instances (DG);
* 10-Nov-2004 : Added new translateShape() and equal(Ellipse2D, Ellipse2D)
* methods (DG);
* 11-Nov-2004 : Renamed translateShape() --> createTranslatedShape() (DG);
* 07-Jan-2005 : Minor Javadoc fix (DG);
* 11-Jan-2005 : Removed deprecated code in preparation for 1.0.0 release (DG);
* 21-Jan-2005 : Modified return type of RectangleAnchor.coordinates()
* method (DG);
* 22-Feb-2005 : Added equality tests for Arc2D and GeneralPath (DG);
* 16-Mar-2005 : Fixed bug where equal(Shape, Shape) fails for two Polygon
* instances (DG);
* 01-Jun-2008 : Fixed bug in equal(GeneralPath, GeneralPath) method (DG);
*
*/
import java.awt.Shape;
import java.awt.geom.AffineTransform;
import java.awt.geom.Point2D;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.util.Collection;
import java.util.Iterator;
/**
* Utility methods for {@link Shape} objects.
*
* @author David Gilbert
*/
public class Main {
/**
* Returns a new collection containing clones of all the items in the
* specified collection.
*
* @param collection
* the collection (<code>null</code> not permitted).
* @return A new collection containing clones of all the items in the
* specified collection.
* @throws CloneNotSupportedException
* if any of the items in the collection cannot be cloned.
*/
public static Collection deepClone(final Collection collection) throws CloneNotSupportedException {
if (collection == null) {
throw new IllegalArgumentException("Null "collection" argument.");
}
// all JDK-Collections are cloneable ...
// and if the collection is not clonable, then we should throw
// a CloneNotSupportedException anyway ...
final Collection result = (Collection) clone(collection);
result.clear();
final Iterator iterator = collection.iterator();
while (iterator.hasNext()) {
final Object item = iterator.next();
if (item != null) {
result.add(clone(item));
} else {
result.add(null);
}
}
return result;
}
/**
* Returns a clone of the specified object, if it can be cloned, otherwise
* throws a CloneNotSupportedException.
*
* @param object
* the object to clone (<code>null</code> not permitted).
* @return A clone of the specified object.
* @throws CloneNotSupportedException
* if the object cannot be cloned.
*/
public static Object clone(final Object object) throws CloneNotSupportedException {
if (object == null) {
throw new IllegalArgumentException("Null "object" argument.");
}
try {
final Method method = object.getClass().getMethod("clone", (Class[]) null);
if (Modifier.isPublic(method.getModifiers())) {
return method.invoke(object, (Object[]) null);
}
} catch (NoSuchMethodException e) {
System.out.println("Object without clone() method is impossible.");
} catch (IllegalAccessException e) {
System.out.println("Object.clone(): unable to call method.");
} catch (InvocationTargetException e) {
System.out.println("Object without clone() method is impossible.");
}
throw new CloneNotSupportedException("Failed to clone.");
}
}</source>



== Framework Interfaces ==

The framework consists of four core interfaces with two specializations for sorting
<OL><LI>Collection</LI><LI>List</LI><LI>Set</LI><LI>Map</LI><LI>SortedSet</LI><LI>SortedMap</LI></OL>

== Interface type and its implementation ==

Interface TypeImplemented bySetHashSet, LinkedHashSet, EnumSetSortedSetTreeSetListVector, Stack, ArrayList, LinkedListQueuePriorityQueue, LinkedListMap<K,V>Hashtable<K,V>, HashMap<K,V>, LinkedHashMap<K,V>, WeakHashMap<K,V>, IdentityHashMap<K,V>SortedMapTreeMap

== Making Your Objects Comparable and Sortable ==

You can make objects comparable by implementing the java.lang.ruparable and java.util.ruparator interfaces.
Classes such as java.lang.String,
java.util.Date, and primitive wrapper classes all implement java.lang.ruparable.



<source lang="java">
import java.util.Arrays;
public class MainClass {
public static void main(String[] args) {
int[] intArray = new int[] { 5, 4, 3, 2, 1 };
Arrays.sort(intArray);
for (int i : intArray) {
System.out.println(i);
}
}
}</source>



<pre class=codeResult>1
2
3
4
5</pre>

== The Collections Framework consists of three parts ==

<OL><LI>interfaces, the abstract data types that the framework supports.</LI><LI>implementations, the concrete versions of these interfaces.</LI><LI>algorithms, the predefined actions that can be defined on either the interfaces or their implementations.</LI></OL>
<OL><LI>All implementations are unsynchronized.</LI><LI>All implementations are serializable and cloneable</LI><LI>All implementations support having null elements.</LI></OL>
The predefined algorithms for supporting the framework are found in the Collections and Arrays classes.

== Using Comparable and Comparator ==

<OL><LI>Implementing java.lang.ruparable enables you to define one way to compare instances of your class.</LI><LI>Objects sometimes might be comparable in more ways.</LI><LI>Comparator defines how two objects should be compared.</LI><LI>To make objects comparable in two ways, you need two comparators.</LI></OL>



<source lang="java">
import java.util.Arrays;
import java.util.ruparator;
class Person implements Comparable {
private String firstName;
private String lastName;
private int age;
public String getFirstName() {
return firstName;
}
public void setFirstName(String firstName) {
this.firstName = firstName;
}
public String getLastName() {
return lastName;
}
public void setLastName(String lastName) {
this.lastName = lastName;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public int compareTo(Object anotherPerson) throws ClassCastException {
if (!(anotherPerson instanceof Person)) {
throw new ClassCastException("A Person object expected.");
}
int anotherPersonAge = ((Person) anotherPerson).getAge();
return this.age - anotherPersonAge;
}
}
class LastNameComparator implements Comparator {
public int compare(Object person, Object anotherPerson) {
String lastName1 = ((Person) person).getLastName().toUpperCase();
String firstName1 = ((Person) person).getFirstName().toUpperCase();
String lastName2 = ((Person) anotherPerson).getLastName().toUpperCase();
String firstName2 = ((Person) anotherPerson).getFirstName().toUpperCase();

if (lastName1.equals(lastName2)) {
return firstName1.rupareTo(firstName2);
} else {
return lastName1.rupareTo(lastName2);
}
}
}
class FirstNameComparator implements Comparator {
public int compare(Object person, Object anotherPerson) {
String lastName1 = ((Person) person).getLastName().toUpperCase();
String firstName1 = ((Person) person).getFirstName().toUpperCase();
String lastName2 = ((Person) anotherPerson).getLastName().toUpperCase();
String firstName2 = ((Person) anotherPerson).getFirstName().toUpperCase();
if (firstName1.equals(firstName2)) {
return lastName1.rupareTo(lastName2);
} else {
return firstName1.rupareTo(firstName2);
}
}
}
public class MainClass {
public static void main(String[] args) {
Person[] persons = new Person[4];
persons[0] = new Person();
persons[0].setFirstName("A");
persons[0].setLastName("X");
persons[0].setAge(56);
persons[1] = new Person();
persons[1].setFirstName("S");
persons[1].setLastName("C");
persons[1].setAge(8);
persons[2] = new Person();
persons[2].setFirstName("E");
persons[2].setLastName("H");
persons[2].setAge(16);
persons[3] = new Person();
persons[3].setFirstName("B");
persons[3].setLastName("Q");
persons[3].setAge(69);
System.out.println("Natural Order");
for (int i = 0; i < 4; i++) {
Person person = persons[i];
String lastName = person.getLastName();
String firstName = person.getFirstName();
int age = person.getAge();
System.out.println(lastName + ", " + firstName + ". Age:" + age);
}
Arrays.sort(persons, new LastNameComparator());
System.out.println();
System.out.println("Sorted by last name");
for (int i = 0; i < 4; i++) {
Person person = persons[i];
String lastName = person.getLastName();
String firstName = person.getFirstName();
int age = person.getAge();
System.out.println(lastName + ", " + firstName + ". Age:" + age);
}
Arrays.sort(persons, new FirstNameComparator());
System.out.println();
System.out.println("Sorted by first name");
for (int i = 0; i < 4; i++) {
Person person = persons[i];
String lastName = person.getLastName();
String firstName = person.getFirstName();
int age = person.getAge();
System.out.println(lastName + ", " + firstName + ". Age:" + age);
}
Arrays.sort(persons);
System.out.println();
System.out.println("Sorted by age");
for (int i = 0; i < 4; i++) {
Person person = persons[i];
String lastName = person.getLastName();
String firstName = person.getFirstName();
int age = person.getAge();
System.out.println(lastName + ", " + firstName + ". Age:" + age);
}
}
}</source>



<pre class=codeResult>Natural Order
X, A. Age:56
C, S. Age:8
H, E. Age:16
Q, B. Age:69
Sorted by last name
C, S. Age:8
H, E. Age:16
Q, B. Age:69
X, A. Age:56
Sorted by first name
X, A. Age:56
Q, B. Age:69
H, E. Age:16
C, S. Age:8
Sorted by age
C, S. Age:8
H, E. Age:16
X, A. Age:56
Q, B. Age:69</pre>

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Admin: 1 версия

в 17:44, 31 мая 2010