Merge pull request #834 from sameira/master

Adding SHA-256 hashing impl and test classes

core-java/src/main/java/com/baeldung/hashing/SHA256Hashing.java

@@ -0,0 +1,51 @@
+package com.baeldung.hashing;
+
+
+import com.google.common.hash.Hashing;
+import org.apache.commons.codec.digest.DigestUtils;
+import org.bouncycastle.util.encoders.Hex;
+
+import java.nio.charset.StandardCharsets;
+import java.security.MessageDigest;
+import java.security.NoSuchAlgorithmException;
+
+public class SHA256Hashing {
+
+    public static String HashWithJavaMessageDigest(final String originalString)
+            throws NoSuchAlgorithmException {
+        final MessageDigest digest = MessageDigest.getInstance("SHA-256");
+        final byte[] encodedhash = digest.digest(
+                originalString.getBytes(StandardCharsets.UTF_8));
+        return bytesToHex(encodedhash);
+    }
+
+    public static String HashWithGuava(final String originalString) {
+        final String sha256hex = Hashing.sha256().hashString(
+                originalString, StandardCharsets.UTF_8).toString();
+        return sha256hex;
+    }
+
+    public static String HashWithApacheCommons(final String originalString) {
+        final String sha256hex = DigestUtils.sha256Hex(originalString);
+        return sha256hex;
+    }
+
+    public static String HashWithBouncyCastle(final String originalString)
+            throws NoSuchAlgorithmException {
+        final MessageDigest digest = MessageDigest.getInstance("SHA-256");
+        final byte[] hash = digest.digest(
+                originalString.getBytes(StandardCharsets.UTF_8));
+        final String sha256hex = new String(Hex.encode(hash));
+        return sha256hex;
+    }
+
+    private static String bytesToHex(byte[] hash) {
+        StringBuffer hexString = new StringBuffer();
+        for (int i = 0; i < hash.length; i++) {
+            String hex = Integer.toHexString(0xff & hash[i]);
+            if(hex.length() == 1) hexString.append('0');
+            hexString.append(hex);
+        }
+        return hexString.toString();
+    }
+}