Java Collections checkedList() Method

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Description

The Java Collections checkedList(List<E>, Class<E>) method is used to get a dynamically typesafe view of the specified list.

Declaration

Following is the declaration for java.util.Collections.checkedList() method.

public static <E> List<E> checkedList(List<E> list,Class<E> type)

Parameters

• list − This is the list for which a dynamically typesafe view is to be returned.

• type − This is the type of element that list is permitted to hold.

Return Value

The method call returns a dynamically typesafe view of the specified list.

Exception

NA

Getting a TypeSafe List from a Collection of Integers Example

The following example shows the usage of Java Collection checkedList(List,Class ) method to get a typesafe view of list of integers. We've created a List object with some integers, printed the original list. Using checkedList(List, Integer) method, we're getting a list of Integer and then it is printed.

package com.tutorialspoint;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;

public class CollectionsDemo {

   public static void main(String[] args) {
      List<Integer> list = new ArrayList<>(Arrays.asList(1,2,3,4,5));

      System.out.println("Initial collection value: " + list);

      List<Integer> safeList = Collections.checkedList(list, Integer.class);
      System.out.println("Typesafe View: "+safeList);
   }
}

Output

Let us compile and run the above program, this will produce the following result.

Initial collection value: [1, 2, 3, 4, 5]
Typesafe View: [1, 2, 3, 4, 5]

Getting a TypeSafe List from a Collection of Strings Example

The following example shows the usage of Java Collection checkedList(List,Class ) method to get a typesafe view of list of strings. We've created a List object with some integers, printed the original list. Using checkedList(List, String) method, we're getting a list of String and then it is printed.

package com.tutorialspoint;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;

public class CollectionsDemo {

   public static void main(String[] args) {
      List<String> list = new ArrayList<>(Arrays.asList("Welcome","to","Tutorialspoint"));

      System.out.println("Initial collection value: " + list);

      List<String> safeList = Collections.checkedList(list, String.class);
      System.out.println("Typesafe View: "+safeList);
   }
}

Output

Let us compile and run the above program, this will produce the following result.

Initial collection value: [Welcome, to, Tutorialspoint]
Typesafe View: [Welcome, to, Tutorialspoint]

Getting a TypeSafe List from a Collection of Objects Example

The following example shows the usage of Java Collection checkedList(List,Class ) method to get a typesafe view of list of Student objects. We've created a List object with some student objects, printed the original list. Using checkedList(List, Student) method, we're getting a list of Students and then it is printed.

package com.tutorialspoint;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;

public class CollectionsDemo {

   public static void main(String[] args) {
      List<Student> list = new ArrayList<>(Arrays.asList(new Student(1, "Julie"),
         new Student(2, "Robert"), new Student(3, "Adam")));

      System.out.println("Initial collection value: " + list);

      List<Student> safeList = Collections.checkedList(list, Student.class);
      System.out.println("Typesafe View: "+safeList);
   }
}
class Student {
   int rollNo;
   String name;

   Student(int rollNo, String name){
      this.rollNo = rollNo;
      this.name = name;
   }

   @Override
   public String toString() {
      return "[ " + this.rollNo + ", " + this.name + " ]";
   }
}

Output

Let us compile and run the above program, this will produce the following result.

Initial collection value: [[ 1, Julie ], [ 2, Robert ], [ 3, Adam ]]
Typesafe View: [[ 1, Julie ], [ 2, Robert ], [ 3, Adam ]]