diff --git a/src/main/java/com/amplitude/api/AmplitudeLog.java b/src/main/java/com/amplitude/api/AmplitudeLog.java
index 52c215a4..2db1b4ef 100644
--- a/src/main/java/com/amplitude/api/AmplitudeLog.java
+++ b/src/main/java/com/amplitude/api/AmplitudeLog.java
@@ -76,17 +76,17 @@ int v(String tag, String msg, Throwable tr) {
         return 0;
     }
 
-    int w(String tag, String msg) {
+    public int w(String tag, String msg) {
         if (enableLogging && logLevel <= Log.WARN) return Log.w(tag, msg);
         return 0;
     }
 
-    int w(String tag, Throwable tr) {
+    public int w(String tag, Throwable tr) {
         if (enableLogging && logLevel <= Log.WARN) return Log.w(tag, tr);
         return 0;
     }
 
-    int w(String tag, String msg, Throwable tr) {
+    public int w(String tag, String msg, Throwable tr) {
         if (enableLogging && logLevel <= Log.WARN) return Log.w(tag, msg, tr);
         return 0;
     }
diff --git a/src/main/java/com/amplitude/identitymanager/Identity.java b/src/main/java/com/amplitude/identitymanager/Identity.java
new file mode 100644
index 00000000..ac3e2121
--- /dev/null
+++ b/src/main/java/com/amplitude/identitymanager/Identity.java
@@ -0,0 +1,84 @@
+package com.amplitude.identitymanager;
+
+import com.amplitude.api.AmplitudeLog;
+
+public class Identity {
+    private String userId;
+    private String deviceId;
+    private boolean shouldUseAdvertisingIdForDeviceId = false;
+    private IdentityListener listener;
+
+    public interface IdentityListener {
+        void onUserIdChanged(String userId);
+        void onDeviceIdChanged(String deviceId);
+    }
+
+    public Identity() {
+        this(false, null);
+    }
+
+    public Identity(boolean useAdvertisingId) {
+        this(useAdvertisingId, null);
+    }
+
+    public Identity(boolean useAdvertisingId, String userId) {
+        this.userId = userId;
+        this.shouldUseAdvertisingIdForDeviceId = useAdvertisingId;
+
+        initializeDeviceId();
+    }
+
+    public String initializeDeviceId(String deviceId) {
+        if (this.deviceId == null) {
+            String deviceIdToUse = "";
+            if (shouldUseAdvertisingIdForDeviceId) {
+                deviceIdToUse = IdentityDeviceInfo.getAdvertisingId();
+            } else {
+                if (deviceId.length() > 0) {
+                    deviceIdToUse = deviceId;
+                } else {
+                    deviceIdToUse = IdentityUtils.generateBase36Id();
+                }
+            }
+            this.deviceId = deviceIdToUse;
+        } else {
+            AmplitudeLog.getLogger().w(Identity.class.getName(), "Cannot set device ID twice for same identity. Skipping operation.");
+        }
+        return this.deviceId;
+    }
+
+    public String initializeDeviceId() {
+        return initializeDeviceId(null);
+    }
+
+    public String getDeviceId() {
+        return deviceId;
+    }
+
+    // Should this exist? Otherwise, when would we call the onDeviceIdChanged listener?
+    public void setDeviceId(String deviceId) {
+        this.deviceId = deviceId;
+        if (listener != null) {
+            listener.onDeviceIdChanged(deviceId);
+        }
+    }
+
+    public String getUserId() {
+        return userId;
+    }
+
+    public void setUserId(String userId) {
+        this.userId = userId;
+        if (listener != null) {
+            listener.onUserIdChanged(userId);
+        }
+    }
+
+    public void addIdentityChangedListener(IdentityListener listener){
+        this.listener = listener;
+    }
+
+    public void useAdvertisingIdForDeviceId() {
+        shouldUseAdvertisingIdForDeviceId = true;
+    }
+}
diff --git a/src/main/java/com/amplitude/identitymanager/IdentityDeviceInfo.java b/src/main/java/com/amplitude/identitymanager/IdentityDeviceInfo.java
new file mode 100644
index 00000000..bf3b6b6d
--- /dev/null
+++ b/src/main/java/com/amplitude/identitymanager/IdentityDeviceInfo.java
@@ -0,0 +1,27 @@
+package com.amplitude.identitymanager;
+
+import android.os.Build;
+
+public class IdentityDeviceInfo {
+    public static String getAdvertisingId() {
+        // This should not be called on the main thread.
+        if ("Amazon".equals(getManufacturer())) {
+            return getAndCacheAmazonAdvertisingId();
+        } else {
+            return getAndCacheGoogleAdvertisingId();
+        }
+    }
+
+    private static String getManufacturer() {
+        return Build.MANUFACTURER;
+    }
+
+    private static String getAndCacheAmazonAdvertisingId() {
+        return "amazonadvertisingid";
+    }
+
+    private static String getAndCacheGoogleAdvertisingId() {
+        return "advertisingid";
+    }
+}
+
diff --git a/src/main/java/com/amplitude/identitymanager/IdentityManager.java b/src/main/java/com/amplitude/identitymanager/IdentityManager.java
new file mode 100644
index 00000000..3125d78e
--- /dev/null
+++ b/src/main/java/com/amplitude/identitymanager/IdentityManager.java
@@ -0,0 +1,23 @@
+package com.amplitude.identitymanager;
+
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+
+public class IdentityManager {
+    static final Map<String, Identity> instanceMap = new ConcurrentHashMap<String, Identity>();
+    private final static String DEFAULT_INSTANCE = "$default_instance";
+
+    public Identity getInstance(String instanceName) {
+        if (instanceMap.containsKey(instanceName)) {
+            return instanceMap.get(instanceName);
+        } else {
+            Identity identityToSet = new Identity();
+            instanceMap.put(instanceName, identityToSet);
+            return identityToSet;
+        }
+    }
+
+    public Identity getInstance() {
+        return getInstance(DEFAULT_INSTANCE);
+    }
+}
diff --git a/src/main/java/com/amplitude/identitymanager/IdentityUtils.java b/src/main/java/com/amplitude/identitymanager/IdentityUtils.java
new file mode 100644
index 00000000..92457789
--- /dev/null
+++ b/src/main/java/com/amplitude/identitymanager/IdentityUtils.java
@@ -0,0 +1,21 @@
+package com.amplitude.identitymanager;
+
+import java.util.Random;
+
+public class IdentityUtils {
+    static private final int device_id_length = 25;
+    static private final String base_36_char_set = "abcdefghijklmnopqrstuvwxyz0123456789";
+    static private final int base_36_radix = 36;
+
+    static String generateBase36Id() {
+        String stringBuilder = "";
+        Random rand = new Random();
+        for (int idx = 0; idx < device_id_length; idx++) {
+            int randomIdx = rand.nextInt(base_36_radix);
+            char nextChar = base_36_char_set.charAt(randomIdx);
+            stringBuilder += nextChar;
+        }
+
+        return stringBuilder;
+    }
+}