Collections checkedMap() method in Java with Examples

Last Updated : 08 Oct, 2018

The checkedMap() method of java.util.Collections class is used to return a dynamically typesafe view of the specified map.

The returned map will be serializable if the specified map is serializable.

Since null is considered to be a value of any reference type, the returned map permits insertion of null keys or values whenever the backing map does.

Syntax:

public static  Map 
    checkedMap(Map m, Class keyType, Class valueType)

Parameters: This method takes the following argument as a parameter:

m – the map for which a dynamically typesafe view is to be returned
keyType – the type of key that m is permitted to hold
valueType – the type of value that m is permitted to hold

Return Value: This method returns a dynamically typesafe view of the specified map.

Below are the examples to illustrate the checkedMap() method

Example 1:

// Java program to demonstrate 
// checkedMap() method 
// for <String, String> value 
  
import java.util.*; 
  
public class GFG1 { 
    public static void main(String[] argv) throws Exception 
    { 
  
        try { 
  
            // creating object of HashMap<String> 
            HashMap<String, String> 
                hmap = new HashMap<String, String>(); 
  
            // Adding elemnet to hmap 
            hmap.put("Ram", "Shyam"); 
            hmap.put("Karan", "Arjun"); 
            hmap.put("Karn", "Veer"); 
            hmap.put("duryodhan", "dhrupat"); 
  
            // printing the map 
            System.out.println("Map: \n" + hmap); 
  
            // create typesafe view of the specified map 
            // using checkedMap() method 
            Map<String, String> 
                tsmap = Collections 
                            .checkedMap(hmap, 
                                        String.class, 
                                        String.class); 
  
            // printing the typesafe view of specified list 
            System.out.println("Typesafe view of Map: " + tsmap); 
        } 
  
        catch (IllegalArgumentException e) { 
            System.out.println("Exception thrown : \n" + e); 
        } 
    } 
} 

Output:

Map: 
{Karn=Veer, Karan=Arjun, duryodhan=dhrupat, Ram=Shyam}
Typesafe view of Map: 
{Karn=Veer, Karan=Arjun, duryodhan=dhrupat, Ram=Shyam}

Example 2:

// Java program to demonstrate 
// checkedMap() method 
// for <String, Integer> value 
  
import java.util.*; 
  
public class GFG1 { 
    public static void main(String[] argv) 
        throws Exception 
    { 
  
        try { 
  
            // creating object of HashMap<String> 
            HashMap<String, Integer> 
                hmap = new HashMap<String, Integer>(); 
  
            // Adding elemnet to hmap 
            hmap.put("Player-1", 20); 
            hmap.put("Player-2", 30); 
            hmap.put("Player-3", 40); 
  
            // printing the map 
            System.out.println("Map: \n" + hmap); 
  
            // create typesafe view of the specified map 
            // using checkedMap() method 
            Map<String, Integer> 
                tsmap = Collections 
                            .checkedMap(hmap, String.class, Integer.class); 
  
            // printing the typesafe view of specified list 
            System.out.println("Typesafe view of Map: \n" + tsmap); 
        } 
  
        catch (IllegalArgumentException e) { 
            System.out.println("Exception thrown : " + e); 
        } 
    } 
} 

Output:

Map: 
{Player-1=20, Player-3=40, Player-2=30}
Typesafe view of Map: 
{Player-1=20, Player-3=40, Player-2=30}

Attention reader! Don’t stop learning now. Get hold of all the important Java Foundation and Collections concepts with the Fundamentals of Java and Java Collections Course at a student-friendly price and become industry ready.

My Personal Notes

Related Articles