diff --git a/java/src/com/zerotier/sdk/VirtualNetworkConfig.java b/java/src/com/zerotier/sdk/VirtualNetworkConfig.java
index c7b48d5c5..0236f813c 100644
--- a/java/src/com/zerotier/sdk/VirtualNetworkConfig.java
+++ b/java/src/com/zerotier/sdk/VirtualNetworkConfig.java
@@ -29,6 +29,8 @@ package com.zerotier.sdk;
 
 import android.util.Log;
 
+import com.zerotier.sdk.util.StringUtils;
+
 import java.lang.Comparable;
 import java.lang.Override;
 import java.lang.String;
@@ -88,11 +90,11 @@ public final class VirtualNetworkConfig implements Comparable<VirtualNetworkConf
         boolean routesEqual = rCurrent.equals(rNew);
 
         if (this.nwid != cfg.nwid) {
-            Log.i(TAG, "nwid Changed. Old: " + Long.toHexString(this.nwid) + " (" + Long.toString(this.nwid) + "), " +
-                    "New: " + Long.toHexString(cfg.nwid) + " (" + Long.toString(cfg.nwid) + ")");
+            Log.i(TAG, "nwid Changed. Old: " + StringUtils.networkIdToString(this.nwid) + " (" + this.nwid + "), " +
+                    "New: " + StringUtils.networkIdToString(cfg.nwid) + " (" + cfg.nwid + ")");
         }
         if (this.mac != cfg.mac) {
-            Log.i(TAG, "MAC Changed. Old: " + Long.toHexString(this.mac) + ", New: " + Long.toHexString(cfg.mac));
+            Log.i(TAG, "MAC Changed. Old: " + StringUtils.macAddressToString(this.mac) + ", New: " + StringUtils.macAddressToString(cfg.mac));
         }
 
         if (!this.name.equals(cfg.name)) {
diff --git a/java/src/com/zerotier/sdk/util/StringUtils.java b/java/src/com/zerotier/sdk/util/StringUtils.java
new file mode 100644
index 000000000..c7bcc5d9f
--- /dev/null
+++ b/java/src/com/zerotier/sdk/util/StringUtils.java
@@ -0,0 +1,52 @@
+/*
+ * ZeroTier One - Network Virtualization Everywhere
+ * Copyright (C) 2011-2023  ZeroTier, Inc.  https://www.zerotier.com/
+ */
+
+package com.zerotier.sdk.util;
+
+public class StringUtils {
+
+    /**
+     * Convert mac address to string.
+     *
+     * @param mac MAC address
+     * @return string in XX:XX:XX:XX:XX:XX format
+     */
+    public static String macAddressToString(long mac) {
+
+        int[] macChars = new int[6];
+        for (int i = 0; i < 6; i++) {
+            macChars[i] = (int) (mac % 256);
+            mac >>= 8;
+        }
+
+        return String.format("%02x:%02x:%02x:%02x:%02x:%02x", macChars[5], macChars[4], macChars[3], macChars[2], macChars[1], macChars[0]);
+    }
+
+    /**
+     * Convert long to hex string.
+     *
+     * @param networkId long
+     * @return string with 0 padding
+     */
+    public static String networkIdToString(long networkId) {
+        return String.format("%016x", networkId);
+    }
+
+    /**
+     * Convert node address to string.
+     *
+     * Node addresses are 40 bits, so print 10 hex characters.
+     *
+     * @param address Node address
+     * @return formatted string
+     */
+    public static String addressToString(long address) {
+        return String.format("%010x", address);
+    }
+
+    public static String etherTypeToString(long etherType) {
+        return String.format("%04x", etherType);
+    }
+}
diff --git a/java/test/com/zerotier/sdk/util/StringUtilsTest.java b/java/test/com/zerotier/sdk/util/StringUtilsTest.java
new file mode 100644
index 000000000..257b14a99
--- /dev/null
+++ b/java/test/com/zerotier/sdk/util/StringUtilsTest.java
@@ -0,0 +1,73 @@
+/*
+ * ZeroTier One - Network Virtualization Everywhere
+ * Copyright (C) 2011-2023  ZeroTier, Inc.  https://www.zerotier.com/
+ */
+
+package com.zerotier.sdk.util;
+
+import static com.google.common.truth.Truth.assertThat;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+@RunWith(JUnit4.class)
+public class StringUtilsTest {
+
+    public StringUtilsTest() {
+    }
+
+    public String oldMacDisplay(long mac) {
+
+        String macStr = Long.toHexString(mac);
+
+        if (macStr.length() > 12) {
+            throw new RuntimeException();
+        }
+
+        while (macStr.length() < 12) {
+            //noinspection StringConcatenationInLoop
+            macStr = "0" + macStr;
+        }
+
+        //noinspection StringBufferReplaceableByString
+        StringBuilder displayMac = new StringBuilder();
+        displayMac.append(macStr.charAt(0));
+        displayMac.append(macStr.charAt(1));
+        displayMac.append(':');
+        displayMac.append(macStr.charAt(2));
+        displayMac.append(macStr.charAt(3));
+        displayMac.append(':');
+        displayMac.append(macStr.charAt(4));
+        displayMac.append(macStr.charAt(5));
+        displayMac.append(':');
+        displayMac.append(macStr.charAt(6));
+        displayMac.append(macStr.charAt(7));
+        displayMac.append(':');
+        displayMac.append(macStr.charAt(8));
+        displayMac.append(macStr.charAt(9));
+        displayMac.append(':');
+        displayMac.append(macStr.charAt(10));
+        displayMac.append(macStr.charAt(11));
+
+        return displayMac.toString();
+    }
+
+    @Test
+    public void testMacDisplay() {
+
+        long mac1 = 1234567891;
+        assertThat(StringUtils.macAddressToString(mac1)).isEqualTo(oldMacDisplay(mac1));
+
+        long mac2 = 999999999;
+        assertThat(StringUtils.macAddressToString(mac2)).isEqualTo(oldMacDisplay(mac2));
+
+        long mac3 = 0x7fffffffffffL;
+        assertThat(StringUtils.macAddressToString(mac3)).isEqualTo(oldMacDisplay(mac3));
+        assertThat(StringUtils.macAddressToString(mac3)).isEqualTo("7f:ff:ff:ff:ff:ff");
+
+        long mac4 = 0x7fafcf3f8fffL;
+        assertThat(StringUtils.macAddressToString(mac4)).isEqualTo(oldMacDisplay(mac4));
+        assertThat(StringUtils.macAddressToString(mac4)).isEqualTo("7f:af:cf:3f:8f:ff");
+    }
+}