в 18:01, 31 мая 2010

2010-05-31T18:01:48Z

Новая страница

== Collections.fill ==



<source lang="java">

import java.util.ArrayList;
import java.util.Collections;
import java.util.LinkedList;
import java.util.List;
import java.util.ListIterator;
class MainClass {
public static void main(String[] args) {
String[] coins = { "A", "B", "C", "D", "E" };
List src = new LinkedList();
for (int i = 0; i < coins.length; i++)
src.add(coins[i]);
List dst = new ArrayList();
for (int i = 0; i < coins.length; i++)
dst.add("");
Collections.copy(dst, src);
ListIterator liter = dst.listIterator();
while (liter.hasNext())
System.out.println(liter.next());
Collections.fill(src, "no coins");
liter = src.listIterator();
while (liter.hasNext())
System.out.println(liter.next());
}
}

</source>



== Collections.min with Comparator ==



<source lang="java">

import java.util.Collections;
import java.util.Set;
import java.util.TreeSet;
class MainClass {
public static void main(String[] args) {
String[] coins = { "Penny", "nickel", "dime", "Quarter", "dollar" };
Set set = new TreeSet();
for (int i = 0; i < coins.length; i++)
set.add(coins[i]);
System.out.println(Collections.min(set));
System.out.println(Collections.min(set, String.CASE_INSENSITIVE_ORDER));
System.out.println("");
System.out.println(Collections.max(set));
System.out.println(Collections.max(set, String.CASE_INSENSITIVE_ORDER));
}
}

</source>



== Collections.reverse ==



<source lang="java">

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.ListIterator;
class UtilDemo3 {
public static void main(String[] args) {
String[] coins = { "A", "B", "C", "D", "E" };
List l = new ArrayList();
for (int i = 0; i < coins.length; i++)
l.add(coins[i]);
ListIterator liter = l.listIterator();
while (liter.hasNext())
System.out.println(liter.next());
Collections.reverse(l);
liter = l.listIterator();
while (liter.hasNext())
System.out.println(liter.next());
}
}

</source>



== Collections.shuffle to shuffle a list ==



<source lang="java">

import java.util.Arrays;
import java.util.Collections;
import java.util.List;
public class MainClass {
public static void main(String[] args) {
List<String> argList = Arrays.asList(args);
Collections.shuffle(argList);
for (String arg : argList) {
System.out.format("%s ", arg);
}
System.out.println();
}
}

</source>



== Create and demonstrate an immutable collection. ==



<source lang="java">

import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.List;
public class Main {
public static void main(String args[]) {
List<Character> list = new ArrayList<Character>();
list.add("X");
System.out.println("Element added to list: " + list.get(0));
Collection<Character> immutableCol = Collections.unmodifiableCollection(list);
immutableCol.add("Y");
}
}

</source>



== Create an empty collection object ==



<source lang="java">

import java.util.Collections;
import java.util.Date;
import java.util.List;
import java.util.Map;
import java.util.Set;
public class Main {
public static void main(String args[]) {
List list = Collections.EMPTY_LIST;
Set set = Collections.EMPTY_SET;
Map map = Collections.EMPTY_MAP;
List<String> s = Collections.emptyList();
Set<Long> l = Collections.emptySet();
Map<Date, String> d = Collections.emptyMap();
}
}

</source>



== Create List containing n Copies of Specified Object Example ==



<source lang="java">

import java.util.Collections;
import java.util.Iterator;
import java.util.List;
public class Main {
public static void main(String[] args) {
List list = Collections.nCopies(5, "A");
Iterator itr = list.iterator();
while (itr.hasNext())
System.out.println(itr.next());
}
}
/*
A
A
A
A
A
*/

</source>



== Demonstrates the use of final collections ==



<source lang="java">

/*
* file: FinalCollections.java
* package: oreilly.hcj.finalstory
*
* This software is granted under the terms of the Common Public License,
* CPL, which may be found at the following URL:
* http://www-124.ibm.ru/developerworks/oss/CPLv1.0.htm
*
* Copyright(c) 2003-2005 by the authors indicated in the @author tags.
* All Rights are Reserved by the various authors.
*
########## DO NOT EDIT ABOVE THIS LINE ########## */
import java.awt.Color;
import java.util.Collections;
import java.util.HashSet;
import java.util.Set;
/**
* Demonstrates the use of final collections.
*
* @author
* @version $Revision: 1.3 $
*/
public static class RainbowBetter {
/** The valid colors of the rainbow. */
public static final Set VALID_COLORS;
static {
Set temp = new HashSet();
temp.add(Color.red);
temp.add(Color.orange);
temp.add(Color.yellow);
temp.add(Color.green);
temp.add(Color.blue);
temp.add(Color.decode("#4B0082")); // indigo
temp.add(Color.decode("#8A2BE2")); // violet
VALID_COLORS = Collections.unmodifiableSet(temp);
}
/**
* Some demo method.
*/
public static final void someMethod() {
Set colors = RainbowBetter.VALID_COLORS;
colors.add(Color.black); // <= exception here
System.out.println(colors);
}
}
}
/* ########## End of File ########## */

</source>



== Making a Collection Read-Only ==



<source lang="java">

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
public class Main {
public static void main(String[] argv) throws Exception {
List stuff = Arrays.asList(new String[] { "a", "b" });
List list = new ArrayList(stuff);
list = Collections.unmodifiableList(list);
try {
list.set(0, "new value");
} catch (UnsupportedOperationException e) {

}
Set set = new HashSet(stuff);
set = Collections.unmodifiableSet(set);
Map map = new HashMap();
map = Collections.unmodifiableMap(map);
}
}

</source>



== Minimum and maximum number in array ==



<source lang="java">

import java.util.Arrays;
import java.util.Collections;
public class Main {
public static void main(String[] args) {
Integer[] numbers = { 8, 2, 6, 7, 0, 1, 4, 9, 5, 3 };
int min = (int) Collections.min(Arrays.asList(numbers));
int max = (int) Collections.max(Arrays.asList(numbers));
System.out.println("Min number: " + min);
System.out.println("Max number: " + max);
}
}

</source>



== Shuffle generic list ==



<source lang="java">

/*
* Copyright (c) 1995 - 2008 Sun Microsystems, Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* - Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* - 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.
*
* - Neither the name of Sun Microsystems nor the names of its
* contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
* IS" AND ANY EXPRESS 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 COPYRIGHT OWNER OR
* 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.
*/
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
public class Deal {
public static void main(String[] args) {
if (args.length < 2) {
System.out.println("Usage: Deal hands cards");
return;
}
int numHands = Integer.parseInt(args[0]);
int cardsPerHand = Integer.parseInt(args[1]);
List<Card> deck = Deck.newDeck();
Collections.shuffle(deck);
if (numHands * cardsPerHand > deck.size()) {
System.out.println("Not enough cards.");
return;
}
for (int i = 0; i < numHands; i++)
System.out.println(dealHand(deck, cardsPerHand));
}
public static ArrayList<Card> dealHand(List<Card> deck, int n) {
int deckSize = deck.size();
List<Card> handView = deck.subList(deckSize - n, deckSize);
ArrayList<Card> hand = new ArrayList<Card>(handView);
handView.clear();
return hand;
}
}
/*
* Copyright (c) 1995 - 2008 Sun Microsystems, Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
* - Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
* - 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.
* - Neither the name of Sun Microsystems nor the names of its contributors may
* be used to endorse or promote products derived from this software without
* specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS 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 COPYRIGHT OWNER OR 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.
*/
class Card {
private final Rank rank;
private final Suit suit;
public Card(Rank rank, Suit suit) {
this.rank = rank;
this.suit = suit;
}
public Rank rank() {
return rank;
}
public Suit suit() {
return suit;
}
public String toString() {
return rank + " of " + suit;
}
}
/*
* Copyright (c) 1995 - 2008 Sun Microsystems, Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
* - Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
* - 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.
* - Neither the name of Sun Microsystems nor the names of its contributors may
* be used to endorse or promote products derived from this software without
* specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS 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 COPYRIGHT OWNER OR 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.
*/
class Deck {
private static final List<Card> protoDeck = new ArrayList<Card>();
// Initialize prototype deck
static {
for (Suit suit : Suit.values())
for (Rank rank : Rank.values())
protoDeck.add(new Card(rank, suit));
}
public static ArrayList<Card> newDeck() {
// Return copy of prototype deck
return new ArrayList<Card>(protoDeck);
}
public static void main(String[] args) {
System.out.println(newDeck());
}
}
/*
* Copyright (c) 1995 - 2008 Sun Microsystems, Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
* - Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
* - 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.
* - Neither the name of Sun Microsystems nor the names of its contributors may
* be used to endorse or promote products derived from this software without
* specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS 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 COPYRIGHT OWNER OR 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.
*/
enum Suit {
CLUBS, DIAMONDS, HEARTS, SPADES
}
/*
* Copyright (c) 1995 - 2008 Sun Microsystems, Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
* - Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
* - 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.
* - Neither the name of Sun Microsystems nor the names of its contributors may
* be used to endorse or promote products derived from this software without
* specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS 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 COPYRIGHT OWNER OR 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.
*/
enum Rank {
DEUCE, THREE, FOUR, FIVE, SIX, SEVEN, EIGHT, NINE, TEN, JACK, QUEEN, KING, ACE
}

</source>



== Shuffle the elements in the array ==



<source lang="java">

import java.util.Arrays;
import java.util.Collections;
public class Main {
public static void main(String[] argv) throws Exception {
String[] array = new String[] { "a", "b", "c" };
Collections.shuffle(Arrays.asList(array));
}
}

</source>



== Shuffling the Elements of a List or Array: use Collections.shuffle() to randomly reorder the elements in a list ==



<source lang="java">

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
public class Main {
public static void main(String[] argv) throws Exception {
List list = new ArrayList();
Collections.shuffle(list);
}
}

</source>



== Sort and Search a LinkedList. ==



<source lang="java">

import java.util.Collections;
import java.util.LinkedList;
import java.util.List;
public class Main {
public static void main(String args[]) {
List<Character> ll = new LinkedList<Character>();
for (char n = "A"; n <= "Z"; n++)
ll.add(n);
Collections.shuffle(ll);
for (Character x : ll)
System.out.print(x + " ");
Collections.sort(ll);
for (Character x : ll)
System.out.print(x + " ");
System.out.println("Searching for F.");
int i = Collections.binarySearch(ll, "F");
if (i >= 0) {
System.out.println("Found at index " + i);
System.out.println("Object is " + ll.get(i));
}
}
}

</source>



== Use Collections.shuffle to shuffle list ==



<source lang="java">

/*
* Copyright (c) 1995 - 2008 Sun Microsystems, Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* - Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* - 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.
*
* - Neither the name of Sun Microsystems nor the names of its
* contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
* IS" AND ANY EXPRESS 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 COPYRIGHT OWNER OR
* 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.
*/
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
public class Shuffle {
public static void main(String[] args) {
List<String> list = Arrays.asList(args);
Collections.shuffle(list);
System.out.println(list);
}
}

</source>



== Use Collections.sort to sort custom class and user defined Comparator ==



<source lang="java">

import java.util.ArrayList;
import java.util.Collections;
import java.util.ruparator;
import java.util.List;
import java.util.ListIterator;
class Employee implements Comparable {
private String name;
private double salary;
Employee(String name, double salary) {
this.name = name;
this.salary = salary;
}
String getName() {
return name;
}
double getSalary() {
return salary;
}
public String toString() {
return "Name = " + getName() + ", Salary = " + getSalary();
}
public int compareTo(Object o) {
if (!(o instanceof Employee))
throw new ClassCastException();
Employee e = (Employee) o;
return name.rupareTo(e.getName());
}
static class SalaryComparator implements Comparator {
public int compare(Object o1, Object o2) {
if (!(o1 instanceof Employee) || !(o2 instanceof Employee))
throw new ClassCastException();
Employee e1 = (Employee) o1;
Employee e2 = (Employee) o2;
return (int) (e1.getSalary() - e2.getSalary());
}
}
}
class UtilDemo4 {
public static void main(String[] args) {
String[] names = { "A", "B", "C", "D" };
double[] salaries = { 2.0, 5.0, 6.0, 4.0 };
List l = new ArrayList();
for (int i = 0; i < names.length; i++)
l.add(new Employee(names[i], salaries[i]));
Collections.sort(l);
ListIterator liter = l.listIterator();
while (liter.hasNext())
System.out.println(liter.next());
Collections.sort(l, new Employee.SalaryComparator());
liter = l.listIterator();
while (liter.hasNext())
System.out.println(liter.next());
}
}

</source>



== Use reverse(), rotate(), and shuffle(). ==



<source lang="java">

import java.util.Collections;
import java.util.LinkedList;
import java.util.List;
public class Main {
public static void main(String args[]) {
List<Character> ll = new LinkedList<Character>();
for (char n = "A"; n <= "F"; n++)
ll.add(n);
System.out.println("Here is the original list: ");
for (Character x : ll)
System.out.print(x + " ");
Collections.reverse(ll);
System.out.println("Here is the reversed list: ");
for (Character x : ll)
System.out.print(x + " ");
Collections.rotate(ll, 2);
for (Character x : ll)
System.out.print(x + " ");
Collections.shuffle(ll);
System.out.println("Here is the randomized list:");
for (Character x : ll)
System.out.print(x + " ");
}
}

</source>

Java/Collections Data Structure/Collections - История изменений

Admin: 1 версия

в 18:01, 31 мая 2010

← Предыдущая	Версия 07:25, 1 июня 2010
(нет различий)