Locale.getDefault(Locale.Category.FORMAT) using reflection in java - java-7

Question

*import java.util.*;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.text.*;
public class LocaleProgram {
public static void main(String[] args) {
try {
Class c = Class.forName("java.util.Locale");
Class c1 = Class.forName("java.util.Locale$Category");
Class[] paramTypes = { c1 };
try {
Method m = c.getMethod("getDefault", paramTypes);
try {
//Object o = m.invoke(c1);
Object o = m.invoke(c1,new Object[]{"FORMAT"});
System.out.println("Object:" + (Locale)o);
} catch (IllegalArgumentException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IllegalAccessException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (InvocationTargetException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
} catch (SecurityException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (NoSuchMethodException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}*
Basically I want Locale.getDefault(Locale.Category.FORMAT) using reflection, so that I can run this code on other than Java version 7.But I am trouble with calling invoke method, it's giving me java.lang.IllegalArgumentException: argument type mismatch exception.
Many thanks in advance

Answer 1

Change this line
Object o = m.invoke(c1,new Object[]{"FORMAT"});
to
Object o = m.invoke(c1,new Object[]{Locale.Category.FORMAT});
However, this may not be what you want, as you want to create the used enum by using reflection?
This will not work under Java 1.6 as these enums didn't exist yet.
Some handy stuff to read: http://blog.ej-technologies.com/2011/12/default-locale-changes-in-java-7.html

Answer 2

As Timmos stated the IllegalArgumentException results from the fact that you pass a String instead of a Locale.Category enum constant. The correct way to get the Locale.Category.FORMAT is by using java.lang.reflect.Field class:
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.Locale;
public class GetDefaultLocale {
public static void main(String[] args){
Locale locale = null;
try {
Class<?> LOCALE_CATEGORY_Class = Class.forName("java.util.Locale$Category");
Class<?> LOCALE_Class = Class.forName("java.util.Locale");
Class<?>[] paramTypes = { LOCALE_CATEGORY_Class };
Method m = LOCALE_Class.getMethod("getDefault", paramTypes);
Field FORMAT_Field = LOCALE_CATEGORY_Class.getField("FORMAT");
//we pass null because the FORMAT is an enumeration constant(the same applies for class variables)
Object FORMAT = FORMAT_Field.get(null);
locale = (Locale)m.invoke(LOCALE_CATEGORY_Class, new Object[]{FORMAT});
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IllegalArgumentException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (NoSuchFieldException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (SecurityException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (NoSuchMethodException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IllegalAccessException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (InvocationTargetException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
//for jre 6
if(locale == null){
locale = Locale.getDefault();
}
}