import java.lang.reflect.*;
public class Foo {
public void bar(int param){
System.out.println(param);
}
public static void main(String args[]){
Object f = new Foo();
try {
Method m = f.getClass().getMethod("bar", int.class);
m.invoke(f, 42);
} catch (Exception e){
System.err.println(e);
}
}
}
$ java Foo
42
Using reflection to change the accessibility of a private object field and access it at runtime.
import java.lang.reflect.Field;
class Life {
private int meaning = 42;
}
class Hack {
public static void main(String args[]){
Life life = new Life();
try {
Field field = life.getClass().getDeclaredField("meaning");
field.setAccessible(true);
System.out.println(field.get(life));
} catch (NoSuchFieldException e) {
e.printStackTrace();
} catch (IllegalAccessException e){
e.printStackTrace();
}
}
}
Output:
42