Create CRC16.java (#3733)

* Create CRC16.java

* Create CRC16Test.java

src/main/java/com/thealgorithms/others/CRC16.java

@@ -0,0 +1,29 @@
+package com.thealgorithms.others;
+
+/**
+ * Generates a crc16 checksum for a given string 
+ */
+public class CRC16 {
+
+    public static void main(String[] args) {
+        System.out.println(crc16("Hello World!"));
+    }
+
+	public static String crc16(String message) {
+		int crc = 0xFFFF; // initial value
+		int polynomial = 0x1021; // 0001 0000 0010 0001 (0, 5, 12)
+		byte[] bytes = message.getBytes();
+
+		for (byte b : bytes) {
+			for (int i = 0; i < 8; i++) {
+				boolean bit = ((b >> (7 - i) & 1) == 1);
+				boolean c15 = ((crc >> 15 & 1) == 1);
+				crc <<= 1;
+				if (c15 ^ bit)
+					crc ^= polynomial;
+			}
+		}
+		crc &= 0xffff;
+		return Integer.toHexString(crc).toUpperCase();
+	}
+}

src/test/java/com/thealgorithms/others/CRC16Test.java

@@ -0,0 +1,23 @@
+package com.thealgorithms.others;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+class CRC16Test {
+
+    CRC16 crc = new CRC16();
+
+    @Test
+    void testCRC16() {
+        // given
+        String textToCRC16 = "hacktoberfest!";
+
+        // when
+        String resultCRC16 = crc.crc16(textToCRC16); // Algorithm CRC16-CCITT-FALSE
+
+        // then
+        assertEquals("10FC", resultCRC16);
+    }
+
+}