How do I get a property name instead of a property value?

Question

I have this class:

public class Person {

    private String name;
    private int age;

}

I want to make an Excel file, and before I put the values into the Excel sheet I need name and age as columns in the sheet. All I need to know is how to get the property names (and NOT the values).

So for example if I have:

name= "Marc"
age= 26

I want to get "name" and "age" first instead of "Marc" and 26. How do I do this?

Just to be clear, the name and number of properties can vary so I can't hardcode "name" and "age", I need some way to iterate and get it. I know how to iterate and put it into the sheet. All I need help with is how to get the property name.

The closest I've got is getDeclaredFields(), but then I can't get further, because I can't get anything from that Field type.

score 2 · Answer 1 · answered Jun 16 '20 at 08:39

2

You can get field name. Here is an example:

Field[] allFields = Person.class.getDeclaredFields();
for(Field f:allFields) 
    System.out.println(f.getName());

answered Jun 16 '20 at 08:39

Ismail H Rana

351
1
9

a.deshpande012 · Accepted Answer · 2020-06-16T08:55:38.433

1

You're on the right track. getDeclaredFields() returns a Field[]. Iterating over this array and accessing the getName() method on each Field should to the trick.

To use your example:

Person p = new Person();
Field[] fields = Person.class.getDeclaredFields();
for (Field field : fields) {
    boolean accessible = field.isAccessible();
    try {
        field.setAccessible(true);
        System.out.println(field.getName() + " - " + field.get(p));
    } catch (IllegalAccessException e) {
        e.printStackTrace();
    } finally {
        field.setAccessible(accessible);
    }
}

edited Jun 16 '20 at 08:55

answered Jun 16 '20 at 08:33

a.deshpande012

715
7
18

1

you should probably also need to set `field.setAccessible(true);` – Lino Jun 16 '20 at 08:49
@Lino Good point, I'll edit that in. – a.deshpande012 Jun 16 '20 at 08:51

score 1 · Answer 3 · answered Jun 16 '20 at 08:36

1

Person.class.getDeclaredFields()

it retun Field[] and you can get information for each Field.

answered Jun 16 '20 at 08:36

Sergey Semendyaev

11
1

score 1 · Answer 4 · answered Jun 16 '20 at 08:40

1

This should work fine. Later you can iterate using the indices of field array to store/write the data.

Field[] fields = YourClassName.class.getFields();

answered Jun 16 '20 at 08:40

darecoder

1,478
2
14
29

score 0 · Answer 5 · answered Jun 16 '20 at 08:44

If you are not bound to use the class as it is, and to avoid using reflexion, I suggest you use a HashMap, so you can add key-value elements. This way you will have 'legal' access to both the name and the value. For example, you can map.put("name", "George"); and then use them as you please. You can check the details here https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html

How do I get a property name instead of a property value?

5 Answers5