diff --git a/sop-java/src/main/java/sop/MicAlg.java b/sop-java/src/main/java/sop/MicAlg.java
deleted file mode 100644
index 5bee787..0000000
--- a/sop-java/src/main/java/sop/MicAlg.java
+++ /dev/null
@@ -1,55 +0,0 @@
-// SPDX-FileCopyrightText: 2022 Paul Schaub <vanitasvitae@fsfe.org>
-//
-// SPDX-License-Identifier: Apache-2.0
-
-package sop;
-
-import java.io.OutputStream;
-import java.io.PrintWriter;
-
-public class MicAlg {
-
-    private final String micAlg;
-
-    public MicAlg(String micAlg) {
-        if (micAlg == null) {
-            throw new IllegalArgumentException("MicAlg String cannot be null.");
-        }
-        this.micAlg = micAlg;
-    }
-
-    public static MicAlg empty() {
-        return new MicAlg("");
-    }
-
-    public static MicAlg fromHashAlgorithmId(int id) {
-        switch (id) {
-            case 1:
-                return new MicAlg("pgp-md5");
-            case 2:
-                return new MicAlg("pgp-sha1");
-            case 3:
-                return new MicAlg("pgp-ripemd160");
-            case 8:
-                return new MicAlg("pgp-sha256");
-            case 9:
-                return new MicAlg("pgp-sha384");
-            case 10:
-                return new MicAlg("pgp-sha512");
-            case 11:
-                return new MicAlg("pgp-sha224");
-            default:
-                throw new IllegalArgumentException("Unsupported hash algorithm ID: " + id);
-        }
-    }
-
-    public String getMicAlg() {
-        return micAlg;
-    }
-
-    public void writeTo(OutputStream outputStream) {
-        PrintWriter pw = new PrintWriter(outputStream);
-        pw.write(getMicAlg());
-        pw.close();
-    }
-}
diff --git a/sop-java/src/main/kotlin/sop/MicAlg.kt b/sop-java/src/main/kotlin/sop/MicAlg.kt
new file mode 100644
index 0000000..58ce7b5
--- /dev/null
+++ b/sop-java/src/main/kotlin/sop/MicAlg.kt
@@ -0,0 +1,34 @@
+// SPDX-FileCopyrightText: 2023 Paul Schaub <vanitasvitae@fsfe.org>
+//
+// SPDX-License-Identifier: Apache-2.0
+
+package sop
+
+import java.io.OutputStream
+import java.io.PrintWriter
+
+data class MicAlg(val micAlg: String) {
+
+    fun writeTo(outputStream: OutputStream) {
+        PrintWriter(outputStream).use { it.write(micAlg) }
+    }
+
+    companion object {
+        @JvmStatic fun empty() = MicAlg("")
+
+        @JvmStatic
+        fun fromHashAlgorithmId(id: Int) =
+            when (id) {
+                1 -> "pgp-md5"
+                2 -> "pgp-sha1"
+                3 -> "pgp-ripemd160"
+                8 -> "pgp-sha256"
+                9 -> "pgp-sha384"
+                10 -> "pgp-sha512"
+                11 -> "pgp-sha224"
+                12 -> "pgp-sha3-256"
+                14 -> "pgp-sha3-512"
+                else -> throw IllegalArgumentException("Unsupported hash algorithm ID: $id")
+            }.let { MicAlg(it) }
+    }
+}
diff --git a/sop-java/src/test/java/sop/MicAlgTest.java b/sop-java/src/test/java/sop/MicAlgTest.java
index 16f54ef..7c6b30a 100644
--- a/sop-java/src/test/java/sop/MicAlgTest.java
+++ b/sop-java/src/test/java/sop/MicAlgTest.java
@@ -18,7 +18,7 @@ public class MicAlgTest {
 
     @Test
     public void constructorNullArgThrows() {
-        assertThrows(IllegalArgumentException.class, () -> new MicAlg(null));
+        assertThrows(NullPointerException.class, () -> new MicAlg(null));
     }
 
     @Test