import java.lang.reflect.Field;

public class FieldAccessDemo{

public static void main(String[] args){

Field f = null;

try{

Class<?> clazz = Class.forName("X");

X x = (X)clazz.newInstance();

f = clazz.getField("i");

System.out.println(f.getInt(x));

f.setInt(x, 20);

System.out.println(f.getInt(x));

f = clazz.getField("PI");

System.out.println(f.getDouble(null)); // The argument is ignored for static field, otherwise NullPointerException will be thrown out.

f.setDouble(x, 20); // It is not accessible with final modifier.

}catch(ClassNotFoundException cnfe){

cnfe.printStackTrace();

}catch(InstantiationException ie){

ie.printStackTrace();

}catch(NoSuchFieldException nsfe){

nsfe.printStackTrace();

}catch(IllegalAccessException iae){

iae.printStackTrace();

}finally{

try{

if(f!=null){

System.out.println(f.getDouble(null));

}

}catch(IllegalAccessException iae){

iae.printStackTrace();

}

}

}

}

class X{

public int i = 10;

public static final double PI = 3.14;

}