Skip to content
Related Articles

Related Articles

Improve Article
Save Article
Like Article

C# | How to retrieve a reference to a specified String

  • Last Updated : 02 Jun, 2021

String.IsInterned(String) Method method is used to retrieve a reference to a specified String. This method looks up the specified string in the intern pool. 
If the specified string has already been interned, a reference to that instance is returned. Otherwise, null is returned. Here the intern pool is a table that contains a single instance of each unique literal string constant declared in a program, as well as any unique instance of String you add programmatically by calling the Intern method.

Note: The main difference between String.Intern(String) Method and String.IsInterned(String) Method is that Intern method returns a reference if the string doesn’t exist by adding a reference of the specified string to the intern pool. But the IsInterned method returns null if the string doesn’t exist.

Syntax: 

public static string IsInterned (string strA);

Here, strA is a string which is used to search for in the intern pool.

Return Value: The return type of this method is System.String. This method will return a reference to strA if it is present in the CLR(Common Language Runtime) intern pool. Otherwise, return null.



Exception: This method will give ArgumentNullException of the str is null.

Below given are some examples to understand the implementation in a better way: 

Example 1: 

C#




// C# program to check if the given
// string is in intern pool or not
using System;
 
class GFG {
     
    // main method
    public static void Main()
    {
        // strings
        string str1 = "Monday";
        string str2 = str1 + "-day";
        string[] pool = {"Tuesday", "Wednesday",
                         "Thursday", str2};
                          
        // checking in intern pool
        foreach(var item in pool)
        {
 
            // retrieve reference of strings
            bool value = String.IsInterned(item) != null;
 
            if (value)
 
                // if the string in intern pool then print
                Console.WriteLine("{0}: Yes", item);
                 
            else
             
                // if string in not intern pool then print
                Console.WriteLine("{0}: No", item);
        }
    }
}

Output: 

Tuesday: Yes
Wednesday: Yes
Thursday: Yes
Monday-day: No

Example 2:

C#




// C# program to check if the given
// string is in intern pool or not
using System;
 
class GFG {
     
    // main method
    public static void Main()
    {
        // strings
        string str1 = "Geeks";
        string str2 = str1 + "-day";
         
        // this will give error as
        // null is present in pool
        string[] pool = {"GFG", "DSA",
                         "C#", null};
                          
        // checking in intern pool
        foreach(var item in pool)
        {
 
            // retrieve reference of strings
            bool value = String.IsInterned(item) != null;
 
            if (value)
 
                // if the string in intern pool then print
                Console.WriteLine("{0}: Yes", item);
                 
            else
             
                // if string in not intern pool then print
                Console.WriteLine("{0}: No", item);
        }
    }
}

Runtime Error:

Unhandled Exception: 
System.ArgumentNullException: Value cannot be null. 
Parameter name: str 
 

Reference:  

 




My Personal Notes arrow_drop_up
Recommended Articles
Page :

Start Your Coding Journey Now!