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<String> arrlist = new ArrayList<String>();
	      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<Integer> arrlist = new ArrayList<Integer>();
	      arrlist.add(10);
	      arrlist.add(20);
	      arrlist.add(30);
	      arrlist.add(40);
	      //Create type safe view of the collection
	      Collection<Integer> 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<String> list = new ArrayList<>();
            list.add("RAJ");
            System.out.println(list);
            List list2 = list;
            list2.add(2);
            System.out.println(list2);
		}
}

Test it Now

Output: