import java.lang.reflect.*;

class Data {
    private int n;

    public Data(int n) {
        this.n = n;
    }

    public int get() {
        return n;
    }
}

public class Reflect {
    public static void main(String[] args) throws Exception {
        Data d = new Data(5);
        Field[] fields = Data.class.getDeclaredFields();
        System.out.println("fields:");
        for (Field f : fields) {
            System.out.println("\t" + f);
        }
        fields[0].setAccessible(true);
        fields[0].setInt(d, 12);
        System.out.println(d.get());
    }
}