The role of Collections.nCopies() is to return an immutable list which contains n copies of given object. This function helps if we want to create a list with n copies of given object. The newly allocated data object is tiny i.e, it contains a single reference to the data object.
Syntax :
public static <T> List<T> nCopies(int number, T object) where, number is the number of copies of object and object represents the element which will appear number times in the returned list. T represents generic type.
Exception : The function throws IllegalArgumentException if value of number is less than 0.
Example :
Java
// Java code to show implementation // of Collections.nCopies() import java.util.*;
class GFG {
// Driver code
public static void main(String[] args)
{
// creating a list where first argument
// represents the number of copies and
// the second argument represents the
// element to be copied for 'number' times
// This will create 4 copies of the objects.
List list = Collections.nCopies( 4 , "GeeksforGeeks" );
// Displaying the list returned
System.out.println( "The list returned is :" );
Iterator itr = list.iterator();
while (itr.hasNext()) {
System.out.print(itr.next() + " " );
}
System.out.println( "\n" );
List list1 = Collections.nCopies( 3 , "GeeksQuiz" );
// Displaying the list returned
System.out.println( "The list returned is :" );
Iterator itr1 = list1.iterator();
while (itr1.hasNext()) {
System.out.print(itr1.next() + " " );
}
System.out.print( "\n" );
}
} |
Output :
The list returned is : GeeksforGeeks GeeksforGeeks GeeksforGeeks GeeksforGeeks The list returned is : GeeksQuiz GeeksQuiz GeeksQuiz