Reflection, or “A Class Named Class” - Java - page 912

public char java.lang.String.charAt(int)
public int java.lang.String.compareTo(java.lang.Object)
public int java.lang.String.compareTo(java.lang.String)

You can see that this could be extended (almost literally) to write a BeanMethods class that
would list only the set/get methods defined in a JavaBean (see Preparing a Class as a
JavaBean ) .

Alternatively, you can find a particular method and invoke it, or find a particular field and
refer to its value. Let's start by finding a given field, because that's the easiest. Example 23-2
is code that, given an Object and the name of a field, finds the field (gets a Field object)
and then retrieves and prints the value of that Field as an int .

Example 23-2. FindField.java
public public class class FindField FindField {

public public static static void void main ( String [] unused )

throws throws NoSuchFieldException , IllegalAccessException {

// Create instance of FindField
FindField gf = new

new FindField ();

// Create instance of target class (YearHolder defined below).
Object o = new

new YearHolder ();

// Use gf to extract a field from o.
System . out . println ( "The value of 'currentYear' is: " +
gf . intFieldValue ( o , "currentYear" ));

}

int int intFieldValue ( Object o , String name )

throws

throws NoSuchFieldException , IllegalAccessException {
Class <?> c = o . getClass ();
Field fld = c . getField ( name );
int int value = fld . getInt ( o );

return

return value ;

}

}

/** This is just a class that we want to get a field from */
class

class YearHolder YearHolder {

/** Just a field that is used to show getting a field's value. */
public public int int currentYear = Calendar . getInstance (). get ( Calendar . YEAR );

}