getFields

Learn field listing with getFields.

Finding fields with getFields

Class.getFields() returns all public fields of a class, including those inherited from superclasses. Each field is represented by a Field object.

Example: Field[] fields = Person.class.getFields(). In the returned array, for each element f.getName() gives the field name and f.getType() gives its type. To get only the class's own fields, use getDeclaredFields; this includes private ones too.

Reading field values

To read the value of a Field object you use get(obj). obj is the instance that holds the field; for static fields you pass null.

Example: Object value = f.get(person). This returns the value of field f on the person instance. To access private fields you must call f.setAccessible(true); otherwise an IllegalAccessException is thrown. This is a common way for libraries to inspect hidden fields in tests.

Exercise Count the public fields of Person

Define a Person class with public String name and public int age fields. Get the fields into a Field[] with Person.class.getFields() and print the length with System.out.println.

Show example solution

import java.lang.reflect.Field;

class Person {
    public String name;
    public int age;
}

public class PersonFields {
    public static void main(String[] args) {
        Field[] fields = Person.class.getFields();
        System.out.println(fields.length);
    }
}

Test yourself

Match the Field methods

getFields

Public fields
getDeclaredFields

All declared
getName

Field name
getType

Field type
Which method returns only public fields, including inherited ones?
- getDeclaredFields
- getFields
- getMethods
- getClasses
Show answer

getFields — getFields returns public ones, including inherited.

Complete the getFields call

Field[] fields = clazz.____();

Show answer

Field[] fields = clazz.getFields();

Next lesson: getMethods

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