Anonymous classes in Java have several advantages, including:

1. Concise code: Anonymous classes can help reduce the amount of boilerplate code needed to create custom objects. They allow developers to define the behavior of an object inline, without having to define a new class.

2. Improved readability: Anonymous classes can improve the readability of the code by keeping related code together. This can make it easier to understand the code and to follow the flow of control.

3. Easy to use: Anonymous classes are easy to use and require minimal setup. They can be created and used on-the-fly, which can save time and effort.

4. Encapsulation: Anonymous classes can be used to encapsulate behavior and data within a single object. This can help to prevent data and behavior from leaking out into the surrounding code.

5. Polymorphism: Anonymous classes can be used to create objects that implement an interface or extend a class without defining a new class. This can help to improve polymorphism and code reuse.

Overall, anonymous classes are a powerful feature of Java that can help to reduce the amount of code needed to create custom objects, improve readability, and encapsulate behavior and data. They are particularly useful in event handling and user interface programming, where custom objects are frequently used. However, they should be used judiciously, as they can make code more difficult to read and debug in certain cases.