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getDeclaredFields is a method in the Java reflection API, defined by the class java.lang.Class. It returns an array of Field objects representing all fields declared by the class or interface represented by the Class object. This includes public, protected, default (package) access, and private fields, but excludes fields inherited from superclasses.

The length of the array returned by getDeclaredFields, accessed as getDeclaredFields().length, gives the number of fields declared directly in that class. This count includes both static and instance fields and may include compiler-generated synthetic fields that the class declares. It does not include fields declared in superclasses or interfaces unless they are declared in the class itself.

In contrast, Class.getFields() returns only public fields and includes those inherited from superclasses, while getDeclaredFields reports all fields declared in the class regardless of their visibility, but not inherited fields. The order of fields in the returned array is not specified and should not be relied upon.

Usage example:

Class<?> cls = MyClass.class;

Field[] declared = cls.getDeclaredFields();

int count = declared.length;

When working with reflection, handling potential SecurityException is advisable, since a security manager may deny access to class metadata. Additionally, since getDeclaredFields() enumerates the class’s own fields, it can be more costly than simply querying field counts in hot paths, so caching results is common when performance is a concern.