Java Collections checkedCollection() Method with Examples

by Online Tutorials Library July 22, 2022

Java Collections checkedCollection() Method

The checkedCollection() is a method of Java Collections class which returns a dynamically typesafe view of the specified collection. If an element inserted of the wrong type, it will result in an immediate ClassCastException.

Syntax

Following is the declaration of checkedCollection() method:

  public static <E> Collection<E> checkedCollection(Collection<E> c, Class<E> type)  

Parameter

Parameter	Description	Required/Optional
c	It is the collection for which a dynamically typesafe view is to be returned.	Required
type	It is the type of element that c is permitted to hold.	Required

Returns

The checkedCollection() method returns a dynamically typesafe view of the specified collection.

Exceptions

ClassCastException

Compatibility Version

Java 1.5 and above

Example 1

  import java.util.*;  public class CollectionsCheckedCollectionExample1 {  public static void main(String[] args) {  //Create list               ArrayList arrlist = new ArrayList();        arrlist.add(“A”);        arrlist.add(“B”);        arrlist.add(“C”);        arrlist.add(“D”);        //Create type safe view of the collection        Collection tslist;        tslist = Collections.checkedCollection(arrlist,String.class);             System.out.println(“Type safe view is: “+tslist);        }  }  

Test it Now

Output:

Type safe view is: [A, B, C, D]

Example 2

  import java.util.*;  public class CollectionsCheckedCollectionExample2 {  public static void main(String[] args) {  //Create list               ArrayList arrlist = new ArrayList();        arrlist.add(10);        arrlist.add(20);        arrlist.add(30);        arrlist.add(40);        //Create type safe view of the collection        Collection tsafelist;        tsafelist = Collections.checkedCollection(arrlist,Integer.class);             System.out.println(“Type safe view is: “+tsafelist);        }  }  

Test it Now

Output:

Type safe view is: [10, 20, 30, 40]

Example 3

  import java.util.*;  public class CollectionsCheckedCollectionExample3 {  public static void main(String[] args) {              Collection c = new ArrayList<>();              c = Collections.checkedCollection(c, String.class);              Collections.addAll(c, “apple”, “banana”);              System.out.println(c);              @SuppressWarnings(“rawtypes”)  Collection c2 = c;              c2.add(1);//this throws exception              System.out.println(c2);  }  }  

Test it Now

Output:

[apple, banana]  Exception in thread "main" java.lang.ClassCastException: Attempt to insert class java.lang.Integer element into collection with element type class java.lang.String  at java.base/java.util.Collections$CheckedCollection.typeCheck(Collections.java:3038)  at java.base/java.util.Collections$CheckedCollection.add(Collections.java:3081)  at myPackage.CollectionCheckedCollectionExample3.main(CollectionCheckedCollectionExample3.java:12)

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Java Collections checkedCollection() Method with Examples

Java Collections checkedCollection() Method

Syntax

Parameter

Returns

Exceptions

Compatibility Version

Example 1

Example 2

Example 3

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