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SHA256 usage implementation in JAVA: sha256 of a text string and file's sha256 checksum verification.

SHA256 Java: sha256 of a text string

        package main;

        import java.security.MessageDigest;
        import java.security.NoSuchAlgorithmException;

        public class HashTextTest {

            /**
             * @param args
             * @throws NoSuchAlgorithmException 
             */
            public static void main(String[] args) throws NoSuchAlgorithmException {
                System.out.println(sha256("test string to sha256"));
            }
            
            static String sha256(String input) throws NoSuchAlgorithmException {
                MessageDigest mDigest = MessageDigest.getInstance("SHA256");
                byte[] result = mDigest.digest(input.getBytes());
                StringBuffer sb = new StringBuffer();
                for (int i = 0; i < result.length; i++) {
                    sb.append(Integer.toString((result[i] & 0xff) + 0x100, 16).substring(1));
                }
                
                return sb.toString();
            }
        }
        

SHA256 Java: verifies file's SHA256 checksum

package main;

import java.io.FileInputStream;
import java.io.IOException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;



public class HashFileTest {
    
    public static void main(String[] args) throws NoSuchAlgorithmException, IOException {
        boolean result = verifyChecksum("/home/eclipse-jee-indigo-SR2-linux-gtk-x86_64.tar.gz", "177750b65a21a9043105fd0820b85b58cf148ae4");
        System.out.println("Does the file's checksum matches the expected one? " + result);
    }
    
    /**
     * Verifies file's SHA256 checksum
     * @param Filepath and name of a file that is to be verified
     * @param testChecksum the expected checksum
     * @return true if the expeceted SHA256 checksum matches the file's SHA256 checksum; false otherwise.
     * @throws NoSuchAlgorithmException
     * @throws IOException
     */
    public static boolean verifyChecksum(String file, String testChecksum) throws NoSuchAlgorithmException, IOException
    {
        MessageDigest sha256 = MessageDigest.getInstance("SHA256");
        FileInputStream fis = new FileInputStream(file);
 
        byte[] data = new byte[1024];
        int read = 0; 
        while ((read = fis.read(data)) != -1) {
            sha256.update(data, 0, read);
        };
        byte[] hashBytes = sha256.digest();
 
        StringBuffer sb = new StringBuffer();
        for (int i = 0; i < hashBytes.length; i++) {
          sb.append(Integer.toString((hashBytes[i] & 0xff) + 0x100, 16).substring(1));
        }
        
        String fileHash = sb.toString();
        
        return fileHash.equals(testChecksum);
    }


}