Make Luna strings considerably faster

luna/src/main/java/org/classdump/luna/ArrayByteString.java

@@ -58,6 +58,10 @@ class ArrayByteString extends ByteString {
       return false;
     }
 
+    if (that instanceof ArrayByteString bstring) {
+      return Arrays.equals(this.bytes, bstring.bytes);
+    }
+
     int len = this.length();
     for (int i = 0; i < len; i++) {
       if (this.byteAt(i) != that.byteAt(i)) {

luna/src/main/java/org/classdump/luna/StringByteString.java

@@ -152,10 +152,15 @@ class StringByteString extends ByteString {
     return string.isEmpty();
   }
 
+  private byte[] bytesCache;
+
   // must not escape, may be an array from the cache!
   private byte[] toBytes() {
-    // TODO: cache the result
-    return string.getBytes(charset);
+    if (bytesCache == null) {
+      bytesCache = string.getBytes(charset);
+    }
+
+    return bytesCache;
   }
 
   @Override