CopyOnWriteArrayList retainAll() method in Java with Examples
Last Updated :
27 Dec, 2018
The Java.util.concurrent.CopyOnArrayList.retainAll() method in Java is used to retain only the elements in the list that are contained in specific collection.
Syntax:
public boolean retainAll(Collection col)
Parameters: This method accepts a mandatory parameter col which is of the type of collection. This is the collection of elements to be retained in this vector.
Return Type: This method returns a boolean value true if the list is changed at all as a result of call else false.
Exception: This method throws a NullPointerException if the specified collection is NULL.
Below Programs illustrate the retainAll() method of CopyOnArrayList in Java:
Program 1: This program involves CopyOnArraylist retainAll() method of Integer Type:
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.*;
public class GFG {
public static void main(String[] args)
{
CopyOnWriteArrayList<Integer> ArrLis1
= new CopyOnWriteArrayList<Integer>();
ArrLis1.add( 34 );
ArrLis1.add( 66 );
ArrLis1.add( 72 );
ArrLis1.add( 10 );
System.out.println( "CopyOnWriteArrayList1: "
+ ArrLis1);
CopyOnWriteArrayList<Integer> ArrLis2
= new CopyOnWriteArrayList<Integer>();
ArrLis2.add( 10 );
ArrLis2.add( 66 );
ArrLis2.add( 97 );
System.out.println( "CopyOnWriteArrayList2: "
+ ArrLis2);
ArrLis2.retainAll(ArrLis1);
System.out.println( "After applying retainAll()"
+ " method on ArrLis2" );
System.out.println( "CopyOnWriteArrayList1: "
+ ArrLis1);
System.out.println( "CopyOnWriteArrayList2: "
+ ArrLis2);
}
}
|
Output:
CopyOnWriteArrayList1: [34, 66, 72, 10]
CopyOnWriteArrayList2: [10, 66, 97]
After applying retainAll() method on ArrLis2
CopyOnWriteArrayList1: [34, 66, 72, 10]
CopyOnWriteArrayList2: [10, 66]
Program 2: This program involves CopyOnArraylist retainAll() method of String Type:
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.*;
public class GFG {
public static void main(String[] args)
{
CopyOnWriteArrayList<String> ArrLis1
= new CopyOnWriteArrayList<String>();
ArrLis1.add( "geeks" );
ArrLis1.add( "shaan" );
ArrLis1.add( "gfg" );
ArrLis1.add( "programming" );
System.out.println( "CopyOnWriteArrayList1: "
+ ArrLis1);
CopyOnWriteArrayList<String> ArrLis2
= new CopyOnWriteArrayList<String>();
ArrLis2.add( "geeks" );
ArrLis2.add( "gfg" );
ArrLis2.add( "qwe" );
System.out.println( "CopyOnWriteArrayList2: "
+ ArrLis2);
ArrLis2.retainAll(ArrLis1);
System.out.println( "After applying retainAll()"
+ " method on ArrLis2" );
System.out.println( "CopyOnWriteArrayList1: "
+ ArrLis1);
System.out.println( "CopyOnWriteArrayList2: "
+ ArrLis2);
}
}
|
Output:
CopyOnWriteArrayList1: [geeks, shaan, gfg, programming]
CopyOnWriteArrayList2: [geeks, gfg, qwe]
After applying retainAll() method on ArrLis2
CopyOnWriteArrayList1: [geeks, shaan, gfg, programming]
CopyOnWriteArrayList2: [geeks, gfg]
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