Java Collections nCopies() Method with Examples

by Online Tutorials Library July 22, 2022

Java Collections nCopies() Method

The nCopies() method of Java Collections class is used to get an immutable list consisting of n copies of the specified object.

Syntax

Following is the declaration of nCopies() method:

Parameter

Parameter	Description	Required/Optional
n	It is the number of elements in the returned list.	Required
o	It is the element to appear repetedly in the returned list.	Required

Returns

The nCopies() method returns an immutable list consisting of n copies of the specified object.

Exceptions

IllegalArgumentException– It throws this exception if the number of elements is less then zero i.e. n < 0.

Compatibility Version

Java 1.4 and above

Example 1

  import java.util.*;  public class CollectionsNCopiesExample1 {  public static void main(String[] args) {  List list = Collections.nCopies(3, “TutorAspire”);              System.out.println(“Output: “+list);              }  }  

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Output:

Output: [TutorAspire, TutorAspire , TutorAspire ]

Example 2

  import java.util.*;  import java.util.concurrent.atomic.AtomicInteger;  public class CollectionsNCopiesExample2 {  public static void main(String[] args) {  AtomicInteger ai = new AtomicInteger();              List list = Collections.nCopies(3, ai);              System.out.println(“Output of Atomic Integer are:”);              System.out.println(list);              ai.incrementAndGet();              System.out.println(list);             }  }  

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Output:

Output of Atomic Integer are:  [0, 0, 0]  [1, 1, 1]

Example 3

  import java.util.*;  public class CollectionsNCopiesExample3 {  public static void main(String[] args) {  List list = Collections.nCopies(5,”SSSIT.COM”);  System.out.println(“List elements: “);  Iterator it = list.iterator();  while(it.hasNext())  System.out.println(it.next());          }  }  

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Output:

List elements:   SSSIT.COM  SSSIT.COM  SSSIT.COM  SSSIT.COM  SSSIT.COM

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Java Collections nCopies() Method with Examples

Java Collections nCopies() Method

Syntax

Parameter

Returns

Exceptions

Compatibility Version

Example 1

Example 2

Example 3

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