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2010-06-01T05:04:09Z

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в 17:44, 31 мая 2010

2010-05-31T17:44:27Z

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== A Least Recently Used Cache ==



<source lang="java">
/**
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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.util.LinkedHashMap;
import java.util.Map;
/**
* A Least Recently Used Cache
*
* @version $Revision: 747062 $
*/
public class LRUCache<K, V> extends LinkedHashMap<K, V> {
private static final long serialVersionUID = -342098639681884413L;
private int maxCacheSize = 10000;
public LRUCache(int maximumCacheSize) {
this(maximumCacheSize, maximumCacheSize, 0.75f, true);
}
/**
* Constructs an empty <tt>LRUCache</tt> instance with the
* specified initial capacity, maximumCacheSize,load factor and ordering mode.
*
* @param initialCapacity the initial capacity.
* @param maximumCacheSize the max capacity.
* @param loadFactor the load factor.
* @param accessOrder the ordering mode - <tt>true</tt> for
* access-order, <tt>false</tt> for insertion-order.
* @throws IllegalArgumentException if the initial capacity is negative
* or the load factor is non positive.
*/
public LRUCache(int initialCapacity, int maximumCacheSize, float loadFactor, boolean accessOrder) {
super(initialCapacity, loadFactor, accessOrder);
this.maxCacheSize = maximumCacheSize;
}
/**
* Returns the maxCacheSize.
*/
public int getMaxCacheSize() {
return maxCacheSize;
}
protected boolean removeEldestEntry(Map.Entry entry) {
return size() > maxCacheSize;
}
}</source>



== Check if a particular element exists in Java LinkedHashSet ==



<source lang="java">
import java.util.LinkedHashSet;
public class Main {
public static void main(String[] args) {
LinkedHashSet<Integer> lhashSet = new LinkedHashSet<Integer>();
lhashSet.add(new Integer("1"));
lhashSet.add(new Integer("2"));
lhashSet.add(new Integer("3"));
System.out.println(lhashSet.contains(new Integer("3")));
}
}</source>



== Check if a particular key exists in Java LinkedHashMap example ==



<source lang="java">
import java.util.LinkedHashMap;
public class Main {
public static void main(String[] args) {
LinkedHashMap<String,String> lHashMap = new LinkedHashMap<String,String>();
lHashMap.put("1", "One");
lHashMap.put("2", "Two");
lHashMap.put("3", "Three");
boolean blnExists = lHashMap.containsKey("3");
System.out.println(blnExists);
}
}</source>



== Check if a particular value exists in Java LinkedHashMap example ==



<source lang="java">
import java.util.LinkedHashMap;
public class Main {
public static void main(String[] args) {
LinkedHashMap<String,String> lHashMap = new LinkedHashMap<String,String>();
lHashMap.put("1", "One");
lHashMap.put("2", "Two");
lHashMap.put("3", "Three");
boolean blnExists = lHashMap.containsValue("Two");
System.out.println(blnExists);
}
}</source>



== Copy all elements of Java LinkedHashSet to an Object Array ==



<source lang="java">
import java.util.LinkedHashSet;
public class Main {
public static void main(String[] args) {
LinkedHashSet<Integer> lhashSet = new LinkedHashSet<Integer>();
lhashSet.add(new Integer("1"));
lhashSet.add(new Integer("2"));
lhashSet.add(new Integer("3"));
Object[] objArray = lhashSet.toArray();
for (Object inte: objArray){
System.out.println(inte);
}
}
}</source>



== Get Set view of Keys from Java LinkedHashMap ==



<source lang="java">
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.Set;
public class Main {
public static void main(String[] args) {
LinkedHashMap<String,String> lHashMap = new LinkedHashMap<String,String>();
lHashMap.put("1", "One");
lHashMap.put("2", "Two");
lHashMap.put("3", "Three");
Set st = lHashMap.keySet();
Iterator itr = st.iterator();
while (itr.hasNext()){
System.out.println(itr.next());
}
st.remove("2");
boolean blnExists = lHashMap.containsKey("2");
System.out.println(blnExists);
}
}
/*
1
2
3
false
*/</source>



== Get Size of Java LinkedHashMap ==



<source lang="java">
import java.util.LinkedHashMap;
public class Main {
public static void main(String[] args) {
LinkedHashMap<String,String> lHashMap = new LinkedHashMap<String,String>();
System.out.println(lHashMap.size());
lHashMap.put("1", "One");
lHashMap.put("2", "Two");
lHashMap.put("3", "Three");
System.out.println(lHashMap.size());
Object obj = lHashMap.remove("2");
System.out.println(lHashMap.size());
}
}</source>



== Iterate through the values of Java LinkedHashMap ==



<source lang="java">
import java.util.Collection;
import java.util.Iterator;
import java.util.LinkedHashMap;
public class Main {
public static void main(String[] args) {
LinkedHashMap<String,String> lHashMap = new LinkedHashMap<String,String>();
lHashMap.put("1", "One");
lHashMap.put("2", "Two");
lHashMap.put("3", "Three");
Collection c = lHashMap.values();
Iterator itr = c.iterator();
while (itr.hasNext()){
System.out.println(itr.next());
}
}
}</source>



== Remove all values from Java LinkedHashMap ==



<source lang="java">
import java.util.LinkedHashMap;
public class Main {
public static void main(String[] args) {
LinkedHashMap<String,String> lHashMap = new LinkedHashMap<String,String>();
lHashMap.put("1", "One");
lHashMap.put("2", "Two");
lHashMap.put("3", "Three");
lHashMap.clear();
System.out.println(lHashMap.size());
}
}</source>



== Remove value from Java LinkedHashMap ==



<source lang="java">
import java.util.LinkedHashMap;
public class Main {
public static void main(String[] args) {
LinkedHashMap<String,String> lHashMap = new LinkedHashMap<String,String>();
lHashMap.put("1", "One");
lHashMap.put("2", "Two");
lHashMap.put("3", "Three");
Object obj = lHashMap.remove("2");
System.out.println(obj + " was Removed");
}
}</source>



== What you can do with a LinkedHashMap. ==



<source lang="java">
import java.util.LinkedHashMap;
public class MainClass {
public static void main(String[] args) {
LinkedHashMap linkedMap = new LinkedHashMap();
for (int i = 0; i < 10; i++) {
linkedMap.put(i, i);
}
System.out.println(linkedMap);
// Least-recently used order:
linkedMap = new LinkedHashMap(16, 0.75f, true);
for (int i = 0; i < 10; i++) {
linkedMap.put(i, i);
}
System.out.println(linkedMap);
for (int i = 0; i < 7; i++)
// Cause accesses:
System.out.println(linkedMap.get(i));
System.out.println(linkedMap);
}
}</source>



<pre class=codeResult>{0=0, 1=1, 2=2, 3=3, 4=4, 5=5, 6=6, 7=7, 8=8, 9=9}
{0=0, 1=1, 2=2, 3=3, 4=4, 5=5, 6=6, 7=7, 8=8, 9=9}
0
1
2
3
4
5
6
{7=7, 8=8, 9=9, 0=0, 1=1, 2=2, 3=3, 4=4, 5=5, 6=6}</pre>

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Admin: 1 версия

в 17:44, 31 мая 2010