Java Collections.checkedCollection() method

The java.util.Collections class consists exclusively of static methods that operate on or return collections. It contains polymorphic algorithms that operate on collections, “wrappers”, which return a new collection backed by a specified collection, and a few other odds and ends.

Collections.checkedCollection() method will returns a dynamically type safe view of the specified collection. Syntax: public static Collection checkedCollection(Collection c, Class type)

Example

package com.w3spoint;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.List;
 
public class Test { 
    public static void main(String a[]){         
        List list = new ArrayList();
        list.add("vikas");
        list.add("mahesh");
        list.add("rahul");
        list.add("amit");
        Collection checkedList = Collections.checkedCollection(list, String.class);
        System.out.println("Checked list content: "+checkedList);
        list.add(10);        
        checkedList.add(90); 
    }
}

Output

Checked list content: [vikas, mahesh, rahul, amit]
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.util.Collections$CheckedCollection.typeCheck(Collections.java:2202)
	at java.util.Collections$CheckedCollection.add(Collections.java:2243)
	at com.w3spoint.Test.main(Test.java:17)

Java Collections class examples

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