KeyStore isCertificateEntry() method in Java with Examples

The isCertificateEntry() method of java.security.KeyStore class is used to check if the specified Certificate entry is present in this KeyStore instance. It returns a boolean value representing the same. 

Syntax:

public final boolean isCertificateEntry(String alias)
    throws KeyStoreException

Parameter: This method accepts the name of the alias as a parameter whose certificate entry to be checked. 

Return Value: This method checks the presence of certificate entry for the requested alias if it exists and returns a boolean value.

Exception: This method throws KeyStoreException if the keystore has not been initialized. 

Note: All the programs in this article won’t run on online IDE as no ‘privatekey’ Keystore exists. You can check this code on the Java compiler on your system. To check this code, create a Keystore ‘privatekey’ on your system and set your own Keystore password to access that Keystore. 

Below are the examples to illustrate the isCertificateEntry() method: 
Example 1:

Java

// Java program to demonstrate isCertificateEntry() method

import java.security.*;
import java.security.cert.*;
import java.util.*;
import java.io.*;

public class GFG {
    public static void main(String[] argv)
    {
        try {

            // creating the object of KeyStore
            // and getting instance
            // By using getInstance() method
            KeyStore sr = KeyStore.getInstance("JKS");

            // keystore password is required to access keystore
            char[] pass = ("123456").toCharArray();

            // creating and initializing object of InputStream
            InputStream is
                = new FileInputStream(
                    "f:/java/private key.store");

            // initializing keystore object
            sr.load(is, pass);

            // checking the presence of certificate entry
            // using isCertificateEntry() method
            Boolean status
                = sr.isCertificateEntry("ftpkey");

            // display the result
            if (status)
                System.out.println(
                    "\nCertificate "
                    + "entry is present");
            else
                System.out.println(
                    "\nCertificate "
                    + "entry is not present");
        }

        catch (NoSuchAlgorithmException e) {

            System.out.println("Exception thrown : " + e);
        }
        catch (NullPointerException e) {

            System.out.println("Exception thrown : " + e);
        }
        catch (KeyStoreException e) {

            System.out.println("Exception thrown : " + e);
        }
        catch (FileNotFoundException e) {

            System.out.println("Exception thrown : " + e);
        }
        catch (IOException e) {

            System.out.println("Exception thrown : " + e);
        }
        catch (CertificateException e) {

            System.out.println("Exception thrown : " + e);
        }
    }
}

Output:

Example 2: For KeyStoreException

Java

// Java program to demonstrate isCertificateEntry() method

import java.security.*;
import java.security.cert.*;
import java.util.*;
import java.io.*;

public class GFG {
    public static void main(String[] argv)
    {
        try {

            // creating the object of KeyStore
            // and getting instance
            // By using getInstance() method
            KeyStore sr = KeyStore.getInstance("JKS");

            // keystore password is required to access keystore
            char[] pass = ("123456").toCharArray();

            // creating and initializing object of InputStream
            InputStream is
                = new FileInputStream(
                    "f:/java/private key.store");

            // initializing keystore object
            // sr.load(is, pass);

            // checking the presence of certificate entry
            // using isCertificateEntry() method
            Boolean status
                = sr.isCertificateEntry("ftpkey");

            // display the result
            if (status)
                System.out.println(
                    "\nCertificate "
                    + "entry is present");
            else
                System.out.println(
                    "\nCertificate "
                    + "entry is not present");
        }
        catch (NullPointerException e) {

            System.out.println("Exception thrown : " + e);
        }
        catch (KeyStoreException e) {

            System.out.println("Exception thrown : " + e);
        }
        catch (FileNotFoundException e) {

            System.out.println("Exception thrown : " + e);
        }
    }
}

Output: Reference: https://docs.oracle.com/javase/9/docs/api/java/security/KeyStore.html#isCertificateEntry-java.lang.String-