how to pass LinkedHashMap to some other collection as a parameter using collections in java
how to pass LinkedHashMap to some other collection as a parameter using collections in java
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In this example we will be passing the LinkedHashMap as a parameter to some other collection that extends the Map interface.
For creating a LinkedHashMap first of all we have to import the java.util package in which the java.util.LinkedHashMap class is contained. In this example we have created a class named CollectionExample in which we have created a LinkedHashMap and added some elements to it
In this example, for adding the contents of the LinkedHashMap to some other Map collection we have used the putAll(Map map) method on the object of the Map collection. The general form of the putAll() method is,
void putAll(Map map)
The above method copies all of the mappings from the specified map to the current Map. In case of the same keys, the value at the key will get replaced.
In the given example we have created a LinkedHashMap and added some elements to it by using the put(Object key, Object value) method on its object.
We have also created a Hashtable named ht and added add the elements of the LinkedHashMap to it by using the putAll(Map map) method on its object and passing LinkedHashMap object as an argument to it.
Then again, we have added all the elements of the Hashtable to the LinkedHashMap by using the putAll(Map map) method on it.
Finally we have displayed the elements of the Hashtable and LinkedHashMap.
package r4r.co.in;
import java.util.*;
public class CollectionExample {
/**
* @param args
*/
public static void main(String args[]) throws IllegalArgumentException, NullPointerException
{
try
{
LinkedHashMap<Integer, Integer> lhm=new LinkedHashMap<Integer, Integer>(); // creating a new LinkedHashMap
lhm.put(1, new Integer(7)); // adding elements to this LinkedHashMap
lhm.put(2, new Integer(5));
lhm.put(3, new Integer(8));
lhm.put(4, new Integer(2));
lhm.put(5, new Integer(9));
lhm.put(6, new Integer(52));
System.out.println("The contents of the LinkedHashMap are as follows: ");
Set set=lhm.entrySet(); // creating a set of the contents of the LinkedHashMap
Iterator itr=set.iterator(); // invoking the iterator on the set created
while(itr.hasNext())
{
Map.Entry<Integer, Integer> map=(Map.Entry<Integer, Integer>)itr.next(); // using the Map.Entry interface
Integer key = map.getKey(); // getting the keys
Integer value = map.getValue(); // getting the values
System.out.print("KEY: "+key); // printing the keys
System.out.print(" "+"VALUE: "+value); // printing the values
System.out.println();
}
lhm.remove(3); // removing the key 3 element
lhm.remove(2); // removing the key 2 element
System.out.println("The contents of the LinkedHashMap after removal of items are: ");
set=lhm.entrySet();
itr=set.iterator();
while(itr.hasNext())
{
Map.Entry<Integer, Integer> map=(Map.Entry<Integer, Integer>)itr.next();
Integer key = map.getKey();
Integer value = map.getValue();
System.out.print("KEY: "+key);
System.out.print(" "+"VALUE: "+value);
System.out.println();
}
System.out.println(lhm.containsKey(2)); // checking whether the LinkedHashMap contains 2 as a key or not
System.out.println(lhm.containsValue(8)); // checking whether the LinkedHashMap contains 8 as an element or not
Hashtable<Integer, Integer> ht= new Hashtable<Integer, Integer>(); // creating a new Hashtable ht
ht.putAll(lhm); // adding the LinkedHashMap lhm to this Hashtable
ht.put(3, new Integer(17)); // adding more elements to the Hashtable
ht.put(2, new Integer(70));
System.out.println("The contents of the Hashtable is as follows: ");
for(int i=1; i<=ht.size(); i++)
{
System.out.println("KEY = "+i+" VALUE = "+ht.get(i));
}
lhm.putAll(ht); // adding the contents of the Hashtable again to the LinkedHashSet lhm
System.out.println("Now the contents of the LinkedHashMap after adding the Hashtable collection to it is: ");
for(int i=1; i<=lhm.size(); i++)
{
System.out.println("KEY = "+i+" VALUE = "+lhm.get(i)); // displaying the contents of the LinkedHashMap
}
}
catch(IllegalArgumentException e)
{
e.printStackTrace();
}
catch(NullPointerException e)
{
e.printStackTrace();
}
}
}
The output of the above given example will be displayed as follows:
The contents of the LinkedHashMap are as follows:
KEY: 1 VALUE: 7
KEY: 2 VALUE: 5
KEY: 3 VALUE: 8
KEY: 4 VALUE: 2
KEY: 5 VALUE: 9
KEY: 6 VALUE: 52
The contents of the LinkedHashMap after removal of items are:
KEY: 1 VALUE: 7
KEY: 4 VALUE: 2
KEY: 5 VALUE: 9
KEY: 6 VALUE: 52
false
false
The contents of the Hashtable is as follows:
KEY = 1 VALUE = 7
KEY = 2 VALUE = 70
KEY = 3 VALUE = 17
KEY = 4 VALUE = 2
KEY = 5 VALUE = 9
KEY = 6 VALUE = 52
Now the contents of the LinkedHashMap after adding the Hashtable collection to it is:
KEY = 1 VALUE = 7
KEY = 2 VALUE = 70
KEY = 3 VALUE = 17
KEY = 4 VALUE = 2
KEY = 5 VALUE = 9
KEY = 6 VALUE = 52
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