Java/Collections Data Structure/LinkedHashMap

Материал из Java эксперт
Перейти к: навигация, поиск

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>
   
  
 
  



Implementing a Least-Recently-Used (LRU) Cache

   <source lang="java">

import java.util.Collections; import java.util.LinkedHashMap; import java.util.Map; public class Main {

 public static void main(String[] argv) throws Exception {
   final int MAX_ENTRIES = 100;
   Map cache = new LinkedHashMap(MAX_ENTRIES + 1, .75F, true) {
     public boolean removeEldestEntry(Map.Entry eldest) {
       return size() > MAX_ENTRIES;
     }
   };
   Object key = "key";
   Object value = "value";
   cache.put(key, value);
   Object o = cache.get(key);
   if (o == null && !cache.containsKey(key)) {
   }
   cache = (Map) Collections.synchronizedMap(cache);
 }

}

</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>
   
  
 
  



Simple Java LinkedHashMap

   <source lang="java">

import java.util.LinkedHashMap; public class Main {

 public static void main(String[] args) {
   LinkedHashMap<String,Integer> lHashMap = new LinkedHashMap<String,Integer>();
   lHashMap.put("One", new Integer(1));
   lHashMap.put("Two", new Integer(2));
   // retrieve value using Object get(Object key) method of Java LinkedHashMap class
   Object obj = lHashMap.get("One");
   System.out.println(obj);
 }

}

</source>