The checkedCollection() method of java.util.Collections class is used to return a dynamically typesafe view of the specified collection
The returned collection does not pass the hashCode and equals operations through to the backing collection, but relies on Object’s equals and hashCode methods. This is necessary to preserve the contracts of these operations in the case that the backing collection is a set or a list.
The returned collection will be serializable if the specified collection is serializable.
Since null is considered to be a value of any reference type, the returned collection permits insertion of null elements whenever the backing collection does.
Syntax:
public static Collection checkedCollection(Collection c, Class type)
Parameters: This method takes the following arguments as a parameter:
- c – the collection for which a dynamically typesafe view is to be returned
- type – the type of element that c is permitted to hold
Return Value: This method returns a dynamically typesafe view of the specified collection
Below are the examples to illustrate the checkedCollection() method
Example 1:
// Java program to demonstrate // checkedCollection() method // for String value import java.util.*; public class GFG1 { public static void main(String[] argv) throws Exception { try { // creating object of List<String> List<String> arlst = new ArrayList<String>(); // Adding element to arrlist arlst.add( "CSS" ); arlst.add( "PHP" ); arlst.add( "HTML" ); arlst.add( "TajMahal" ); // printing the arrlist System.out.println( "List: " + arlst); // create typesafe view of the collection Collection<String> tslst = Collections .checkedCollection(arlst, String. class ); // printing the arrlist after operation System.out.println( "Typesafe view of List: " + tslst); } catch (IllegalArgumentException e) { System.out.println( "Exception thrown : " + e); } } } |
List: [CSS, PHP, HTML, TajMahal] Typesafe view of List: [CSS, PHP, HTML, TajMahal]
Example 2:
// Java program to demonstrate // checkedCollection() method // for Integer value import java.util.*; public class GFG1 { public static void main(String[] argv) throws Exception { try { // creating object of List<Integer> List<Integer> arlst = new ArrayList<Integer>(); // Adding element to arrlist arlst.add( 20 ); arlst.add( 30 ); arlst.add( 40 ); arlst.add( 50 ); // printing the arrlist System.out.println( "List: " + arlst); // create typesafe view of the collection Collection<Integer> tslst = Collections .checkedCollection(arlst, Integer. class ); // printing the arrlist after operation System.out.println( "Typesafe view of List: " + tslst); } catch (IllegalArgumentException e) { System.out.println( "Exception thrown : " + e); } } } |
List: [20, 30, 40, 50] Typesafe view of List: [20, 30, 40, 50]
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