Java Collections checkedList() Method with Examples

by Online Tutorials Library July 22, 2022

Java Collections checkedList() Method

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

Syntax

Following is the declaration of checkedList() method:

Parameter

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

Returns

The checkedList() method returns a dynamically typesafe view of the specified List.

Exceptions

ClassCastException

Compatibility Version

Java 1.5 and above

Example 1

  import java.util.*;  public class CollectionsCheckedListExample1 {  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 List                  System.out.println(“Type safe view of the List is: “+Collections.checkedList(arrlist,String.class));        }  }  

Test it Now

Output:

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

Example 2

  import java.util.*;  public class CollectionsCheckedListExample2 {  public static void main(String[] args) {    List myList = new ArrayList();          myList.add(“one”);          myList.add(“two”);          myList.add(“three”);          myList.add(“four”);          List chkList = Collections.checkedList(myList, String.class);          System.out.println(“Checked list content: “+chkList);          //you can add any type of elements to myList object          myList.add(10);          //you cannot add any type of elements to chkList object, doing so throws ClassCastException          chkList.add(10); //throws ClassCastException    }  }  

Test it Now

Output:

Checked list content: [one, two, three, four]  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.CollectionCheckedListExample2.main(CollectionCheckedListExample2.java:15)

Example 3

  import java.util.*;  public class CollectionsCheckedListExample3 {  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.checkedList(arrlist,Integer.class);             System.out.println(“Type safe view of the List is: “+tsafelist);        }  }  

Test it Now

Output:

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

Example 4

  import java.util.*;  public class CollectionsCheckedListExample4 {  public static void main(String[] args) {              List list = new ArrayList<>();              list.add(“RAJ”);              System.out.println(list);              List list2 = list;              list2.add(2);              System.out.println(list2);  }  }  

Test it Now

Output:

[RAJ]  [RAJ, 2]

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Java Collections checkedList() Method with Examples

Java Collections checkedList() Method

Syntax

Parameter

Returns

Exceptions

Compatibility Version

Example 1

Example 2

Example 3

Example 4

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