The first phones, tablets, and TV boxes with Android 5.0 software should begin shipping in a few weeks, and Google will begin rolling out Android 5.0 as an over-the-air updates to owners of recent Nexus devices soon.
To help developers get their apps ready, Google has released the software developer kit for Android 5.0 Lollipop.
Preview images are also available for the Nexus 5 smartphone and Nexus 7 (2013) tablet.
You can flash those images to load Android 5.0 on a GSM Nexus 5 or WiFi-only Nexus 7, but you’ll overwrite your existing data in the process. If you want to simply upgrade from Android 4.4 you’ll want to wait for an over-the-air update (or an unofficial, flashable ROM based on the new images).
The Android 5.0 SDK includes tools for developing Android apps that use Google’s new Material design language as well as other features included in the latest version of Android such as USB audio, low latency audio, camera improvements, and heads-up notifications.
The SDK also provides tools for developing Android TV apps designed for big screen displays.