Initial data commit

Task/Vigen-re-cipher/Java/vigen-re-cipher-2.java

@@ -0,0 +1,58 @@
+import com.google.common.collect.Streams;
+import java.util.function.Supplier;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+import static java.nio.charset.StandardCharsets.US_ASCII;
+
+public class VigenereCipher {
+    private final static int LOWER = 'A';
+    private final static int UPPER = 'Z';
+    private final static int SIZE = UPPER - LOWER + 1;
+    private final Supplier<Stream<Character>> maskStream;
+
+    public VigenereCipher(final String key) {
+        final String mask = new String(key.getBytes(US_ASCII)).toUpperCase();
+        maskStream = () ->
+                Stream.iterate(0, i -> (i+1) % mask.length()).map(mask::charAt);
+    }
+
+    private String transform(final String text, final boolean encode) {
+        final Stream<Integer> textStream = text.toUpperCase().chars().boxed()
+                .filter(i -> i >= LOWER && i <= UPPER);
+        return Streams.zip(textStream, maskStream.get(), (c, m) ->
+                encode ? c + m - 2 * LOWER : c - m + SIZE)
+            .map(c -> Character.toString(c % SIZE + LOWER))
+            .collect(Collectors.joining());
+    }
+
+    public String encrypt(final String plaintext) {
+        return transform(plaintext,true);
+    }
+
+    public String decrypt(final String ciphertext) {
+        return transform(ciphertext,false);
+    }
+}
+
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+class VigenereCipherTest {
+    private static final VigenereCipher Vigenere = new VigenereCipher("VIGENERECIPHER");
+
+    @Test
+    @DisplayName("encipher/decipher round-trip succeeds")
+    void vigenereCipherTest() {
+        final String input = "Beware the Jabberwock, my son! The jaws that bite, the claws that catch!";
+        final String expectEncrypted = "WMCEEIKLGRPIFVMEUGXQPWQVIOIAVEYXUEKFKBTALVXTGAFXYEVKPAGY";
+        final String expectDecrypted = "BEWARETHEJABBERWOCKMYSONTHEJAWSTHATBITETHECLAWSTHATCATCH";
+
+        final String ciphertext = Vigenere.encrypt(input);
+        assertEquals(expectEncrypted, ciphertext);
+
+        final String plaintext = Vigenere.decrypt(ciphertext);
+        assertEquals(expectDecrypted, plaintext);
+    }
+
+}