The checkedList() method of Collections class is present inside java.util package is used to return a dynamically typesafe view of the specified list. The key thing to note here is that the returned list will be serializable if the specified list is serializable. Since null is considered to be a value of any reference type, the returned list permits the insertion of null elements whenever the backing list does.
Tip: This method is compatible with java version 1.5 and onwards.
Syntax:
public static List checkedList(List list, Class type)
Parameters: This method takes the following arguments as parameters:
- The list for which a dynamically typesafe view is to be returned
- The type of element that list is permitted to hold
Return Type: A dynamically typesafe view of the specified list.
Exceptions: This method throws ClassCastException
Example 1:
Java
// Java program to Demonstrate checkedList() method// of Collections class for a string value// Importing required classesimport java.util.*;// Main classpublic class GFG { // Main driver method public static void main(String[] argv) throws Exception { // Try block to check for exceptions try { // Creating an ArrayList of string type by // declaring object of List List<String> arlst = new ArrayList<String>(); // Adding element to ArrayList // by using standard add() method // Custom input elements arlst.add("A"); arlst.add("B"); arlst.add("C"); arlst.add("TajMahal"); // Printing the above elements inside ArrayList System.out.println("List: " + arlst); // Creating typesafe view of the specified list // and applying checkedList List<String> tslst = Collections.checkedList( arlst, String.class); // Printing the updated elements of ArrayList // after applying above operation System.out.println("Typesafe view of List: " + tslst); } // Catch block to handle the exceptions catch (IllegalArgumentException e) { // Display message on console if exception // occurs System.out.println("Exception thrown : " + e); } }} |
Output:
List: [A, B, C, TajMahal] Typesafe view of List: [A, B, C, TajMahal]
Example 2:
Java
// Java program to Demonstrate checkedList() method// of Collections class for a string value// Importing required classesimport java.util.*;// Main classpublic class GFG { // Main driver method public static void main(String[] argv) throws Exception { // Try block to check for exceptions try { // Creating an empty ArrayList of integer type // by creating an object of List List<Integer> arlst = new ArrayList<Integer>(); // Adding element to above ArrayList // by using add() method arlst.add(20); arlst.add(30); arlst.add(40); arlst.add(50); // Printing the elements of above ArrayList System.out.println("List: " + arlst); // Creating typesafe view of the specified list // with usage of checkedList() method List<Integer> tslst = Collections.checkedList( arlst, Integer.class); // Printing the elements of ArrayList // after performing above operation System.out.println("Typesafe view of List: " + tslst); } // Catch block to handle the exceptions catch (IllegalArgumentException e) { // Display message if exception occurs System.out.println("Exception thrown : " + e); } }} |
Output:
List: [20, 30, 40, 50] Typesafe view of List: [20, 30, 40, 50]