Mega Code Archive
Generic Reflection Test
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/*
This program is a part of the companion code for Core Java 8th ed.
(http://horstmann.com/corejava)
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
import java.lang.reflect.GenericArrayType;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.lang.reflect.TypeVariable;
import java.lang.reflect.WildcardType;
import java.util.Arrays;
import java.util.Scanner;
/**
* @version 1.10 2007-05-15
* @author Cay Horstmann
*/
public class GenericReflectionTest
{
public static void main(String[] args)
{
// read class name from command line args or user input
String name;
if (args.length > 0) name = args[0];
else
{
Scanner in = new Scanner(System.in);
System.out.println("Enter class name (e.g. java.util.Collections): ");
name = in.next();
}
try
{
// print generic info for class and public methods
Class<?> cl = Class.forName(name);
printClass(cl);
for (Method m : cl.getDeclaredMethods())
printMethod(m);
}
catch (ClassNotFoundException e)
{
e.printStackTrace();
}
}
public static void printClass(Class<?> cl)
{
System.out.print(cl);
printTypes(cl.getTypeParameters(), "<", ", ", ">", true);
Type sc = cl.getGenericSuperclass();
if (sc != null)
{
System.out.print(" extends ");
printType(sc, false);
}
printTypes(cl.getGenericInterfaces(), " implements ", ", ", "", false);
System.out.println();
}
public static void printMethod(Method m)
{
String name = m.getName();
System.out.print(Modifier.toString(m.getModifiers()));
System.out.print(" ");
printTypes(m.getTypeParameters(), "<", ", ", "> ", true);
printType(m.getGenericReturnType(), false);
System.out.print(" ");
System.out.print(name);
System.out.print("(");
printTypes(m.getGenericParameterTypes(), "", ", ", "", false);
System.out.println(")");
}
public static void printTypes(Type[] types, String pre, String sep, String suf,
boolean isDefinition)
{
if (pre.equals(" extends ") && Arrays.equals(types, new Type[] { Object.class })) return;
if (types.length > 0) System.out.print(pre);
for (int i = 0; i < types.length; i++)
{
if (i > 0) System.out.print(sep);
printType(types[i], isDefinition);
}
if (types.length > 0) System.out.print(suf);
}
public static void printType(Type type, boolean isDefinition)
{
if (type instanceof Class)
{
Class<?> t = (Class<?>) type;
System.out.print(t.getName());
}
else if (type instanceof TypeVariable)
{
TypeVariable<?> t = (TypeVariable<?>) type;
System.out.print(t.getName());
if (isDefinition)
printTypes(t.getBounds(), " extends ", " & ", "", false);
}
else if (type instanceof WildcardType)
{
WildcardType t = (WildcardType) type;
System.out.print("?");
printTypes(t.getUpperBounds(), " extends ", " & ", "", false);
printTypes(t.getLowerBounds(), " super ", " & ", "", false);
}
else if (type instanceof ParameterizedType)
{
ParameterizedType t = (ParameterizedType) type;
Type owner = t.getOwnerType();
if (owner != null)
{
printType(owner, false);
System.out.print(".");
}
printType(t.getRawType(), false);
printTypes(t.getActualTypeArguments(), "<", ", ", ">", false);
}
else if (type instanceof GenericArrayType)
{
GenericArrayType t = (GenericArrayType) type;
System.out.print("");
printType(t.getGenericComponentType(), isDefinition);
System.out.print("[]");
}
}
}
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