Field: Class> getType()
import java.lang.reflect.Field; public class Main { public static void initIntFields(final Object obj) { try { Field[] fields = obj.getClass().getDeclaredFields(); for (int idx = 0; idx < fields.length; idx++) { if (fields[idx].getType() == int.class) { fields[idx].setAccessible(true); fields[idx].setInt(obj, 0); } } } catch (final IllegalAccessException ex) { throw new RuntimeException(ex); } } public static final void main(final String[] args) { Integer value = new Integer("123"); System.out.println("Before: " + value); initIntFields(value); System.out.println("After: " + value); } }