Java/Collections Data Structure/LinkedHashMap

Check if a particular element exists in Java LinkedHashSet

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")));
  }
}

Check if a particular key exists in Java LinkedHashMap example

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);
  }
}

Check if a particular value exists in Java LinkedHashMap example

       
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);
  }
}

Copy all elements of Java LinkedHashSet to an Object Array

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);
    }
  }
}

Get Set view of Keys from Java LinkedHashMap

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
*/

Get Size of Java LinkedHashMap

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());
  }
}

Implementing a Least-Recently-Used (LRU) Cache

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);
  }
}

Iterate through the values of Java LinkedHashMap

       
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());
    }
  }
}

Remove all values from Java LinkedHashMap

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());
  }
}

Remove value from Java LinkedHashMap

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");
  }
}

Simple Java LinkedHashMap

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);
  }
}