What are the rules for automatic type conversion in Java?

In Java, automatic type conversion follows the following rules:

1. When a small data type is operated with a larger data type, the small data type will be automatically converted to the larger data type.
2. When an integer type is converted to a floating point type, the integer type will be automatically converted to a floating point type.
3. When a literal decimal number is assigned to an integer type without using any identifier, the integer type will automatically be converted to a floating-point type.
4. When an object type is converted to its subclass type, the object type is automatically converted to the subclass type.
5. When a method returns a value that needs to be assigned to a variable of a different type, the returned value will be automatically converted to the type of the receiving variable.

It’s important to be aware that when converting a data type from a larger one to a smaller one, data loss or overflow may occur. Therefore, developers need to handle this type of conversion carefully.