Hex Representation of a SHA-1 Digest of a String in Java (#14239)

* Hex Representation of a SHA-1 Digest of a String in Java

* Hex Representation of a SHA-1 Digest of a String in Java

* Hex Representation of a SHA-1 Digest of a String in Java

core-java-modules/core-java-security-3/src/test/java/com/baeldung/crypto/sha1/HexRepresentationSha1DigestUnitTest.java

@@ -0,0 +1,42 @@
+package com.baeldung.crypto.sha1;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+import java.nio.charset.StandardCharsets;
+import java.security.MessageDigest;
+import java.security.NoSuchAlgorithmException;
+
+import org.apache.commons.codec.digest.DigestUtils;
+import org.junit.jupiter.api.Test;
+
+import com.google.common.hash.Hashing;
+
+public class HexRepresentationSha1DigestUnitTest {
+
+    String input = "Hello, World";
+    String expectedHexValue = "907d14fb3af2b0d4f18c2d46abe8aedce17367bd";
+
+    @Test
+    public void givenMessageDigest_whenUpdatingWithData_thenDigestShouldMatchExpectedValue() throws NoSuchAlgorithmException {
+        MessageDigest md = MessageDigest.getInstance("SHA-1");
+        md.update(input.getBytes(StandardCharsets.UTF_8));
+
+        StringBuilder hexString = new StringBuilder();
+        byte[] digest = md.digest();
+
+        for (byte b : digest) {
+            hexString.append(String.format("%02x", b));
+        }
+        assertEquals(expectedHexValue, hexString.toString());
+    }
+
+    @Test
+    public void givenDigestUtils_whenCalculatingSHA1Hex_thenDigestShouldMatchExpectedValue() {
+        assertEquals(expectedHexValue, DigestUtils.sha1Hex(input));
+    }
+
+    @Test
+    public void givenHashingLibrary_whenCalculatingSHA1Hash_thenDigestShouldMatchExpectedValue() {
+        assertEquals(expectedHexValue, Hashing.sha1().hashString(input, StandardCharsets.UTF_8).toString());
+    }
+}