Admin: 1 версия

2010-06-01T06:01:28Z

1 версия

в 18:01, 31 мая 2010

2010-05-31T18:01:43Z

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== Deal with enum type and its method ==



<source lang="java">
/*
* Copyright (c) 1995 - 2008 Sun Microsystems, Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* - Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* - Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* - Neither the name of Sun Microsystems nor the names of its
* contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
* IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
* THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
import static java.lang.System.out;
import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
enum Charge {
POSITIVE, NEGATIVE, NEUTRAL;
Charge() {
out.format("under construction%n");
}
}
public class EnumTrouble {
public static void main(String... args) {
try {
Class<?> c = Charge.class;
Constructor[] ctors = c.getDeclaredConstructors();
for (Constructor ctor : ctors) {
out.format("Constructor: %s%n", ctor.toGenericString());
ctor.setAccessible(true);
ctor.newInstance();
}
// production code should handle these exceptions more gracefully
} catch (InstantiationException x) {
x.printStackTrace();
} catch (IllegalAccessException x) {
x.printStackTrace();
} catch (InvocationTargetException x) {
x.printStackTrace();
}
}
}
</source>



== Deal with enum type field ==



<source lang="java">

/*
* Copyright (c) 1995 - 2008 Sun Microsystems, Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* - Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* - Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* - Neither the name of Sun Microsystems nor the names of its
* contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
* IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
* THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
import java.lang.reflect.Field;
enum E0 {
A, B
}
enum E1 {
A, B
}
class ETest {
private E0 fld = E0.A;
}
public class EnumTroubleToo {
public static void main(String... args) {
try {
ETest test = new ETest();
Field f = test.getClass().getDeclaredField("fld");
f.setAccessible(true);
f.set(test, E1.A); // IllegalArgumentException
// production code should handle these exceptions more gracefully
} catch (NoSuchFieldException x) {
x.printStackTrace();
} catch (IllegalAccessException x) {
x.printStackTrace();
}
}
}
</source>



== Deal with Enum Type in reflection ==



<source lang="java">
/*
* Copyright (c) 1995 - 2008 Sun Microsystems, Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* - Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* - Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* - Neither the name of Sun Microsystems nor the names of its
* contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
* IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
* THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
import static java.lang.System.out;
import java.lang.reflect.Field;
import java.util.Arrays;
enum Tweedle {
DEE, DUM
}
public class Book {
public long chapters = 0;
public String[] characters = { "Alice", "White Rabbit" };
public Tweedle twin = Tweedle.DEE;
public static void main(String... args) {
Book book = new Book();
String fmt = "%6S: %-12s = %s%n";
try {
Class<?> c = book.getClass();
Field chap = c.getDeclaredField("chapters");
out.format(fmt, "before", "chapters", book.chapters);
chap.setLong(book, 12);
out.format(fmt, "after", "chapters", chap.getLong(book));
Field chars = c.getDeclaredField("characters");
out.format(fmt, "before", "characters", Arrays.asList(book.characters));
String[] newChars = { "Queen", "King" };
chars.set(book, newChars);
out.format(fmt, "after", "characters", Arrays.asList(book.characters));
Field t = c.getDeclaredField("twin");
out.format(fmt, "before", "twin", book.twin);
t.set(book, Tweedle.DUM);
out.format(fmt, "after", "twin", t.get(book));
// production code should handle these exceptions more gracefully
} catch (NoSuchFieldException x) {
x.printStackTrace();
} catch (IllegalAccessException x) {
x.printStackTrace();
}
}
}
</source>



== Enum Spy ==



<source lang="java">
/*
* Copyright (c) 1995 - 2008 Sun Microsystems, Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* - Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* - Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* - Neither the name of Sun Microsystems nor the names of its
* contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
* IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
* THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
import static java.lang.System.out;
import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.Member;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.List;
public class EnumSpy {
private static final String fmt = " %11s: %s %s%n";
public static void main(String... args) {
try {
Class<?> c = Class.forName(args[0]);
if (!c.isEnum()) {
out.format("%s is not an enum type%n", c);
return;
}
out.format("Class: %s%n", c);
Field[] flds = c.getDeclaredFields();
List<Field> cst = new ArrayList<Field>(); // enum constants
List<Field> mbr = new ArrayList<Field>(); // member fields
for (Field f : flds) {
if (f.isEnumConstant())
cst.add(f);
else
mbr.add(f);
}
if (!cst.isEmpty())
print(cst, "Constant");
if (!mbr.isEmpty())
print(mbr, "Field");
Constructor[] ctors = c.getDeclaredConstructors();
for (Constructor ctor : ctors) {
out.format(fmt, "Constructor", ctor.toGenericString(), synthetic(ctor));
}
Method[] mths = c.getDeclaredMethods();
for (Method m : mths) {
out.format(fmt, "Method", m.toGenericString(), synthetic(m));
}
// production code should handle this exception more gracefully
} catch (ClassNotFoundException x) {
x.printStackTrace();
}
}
private static void print(List<Field> lst, String s) {
for (Field f : lst) {
out.format(fmt, s, f.toGenericString(), synthetic(f));
}
}
private static String synthetic(Member m) {
return (m.isSynthetic() ? "[ synthetic ]" : "");
}
}
</source>



== Enum type as class ==



<source lang="java">
/*
* Copyright (c) 1995 - 2008 Sun Microsystems, Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* - Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* - Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* - Neither the name of Sun Microsystems nor the names of its
* contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
* IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
* THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
import static java.lang.System.out;
import java.util.Arrays;
enum Eon {
HADEAN, ARCHAEAN, PROTEROZOIC, PHANEROZOIC
}
public class EnumConstants {
public static void main(String... args) {
try {
Class<?> c = (args.length == 0 ? Eon.class : Class.forName(args[0]));
out.format("Enum name: %s%nEnum constants: %s%n", c.getName(), Arrays
.asList(c.getEnumConstants()));
if (c == Eon.class)
out.format(" Eon.values(): %s%n", Arrays.asList(Eon.values()));
// production code should handle this exception more gracefully
} catch (ClassNotFoundException x) {
x.printStackTrace();
}
}
}
</source>



== Get and set value of a Enum type field ==



<source lang="java">
/*
* Copyright (c) 1995 - 2008 Sun Microsystems, Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* - Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* - Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* - Neither the name of Sun Microsystems nor the names of its
* contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
* IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
* THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
import static java.lang.System.out;
import java.lang.reflect.Field;
enum TraceLevel {
OFF, LOW, MEDIUM, HIGH, DEBUG
}
class MyServer {
private TraceLevel level = TraceLevel.OFF;
}
public class SetTrace {
public static void main(String... args) {
TraceLevel newLevel = TraceLevel.valueOf(args[0]);
try {
MyServer svr = new MyServer();
Class<?> c = svr.getClass();
Field f = c.getDeclaredField("level");
f.setAccessible(true);
TraceLevel oldLevel = (TraceLevel) f.get(svr);
out.format("Original trace level: %s%n", oldLevel);
if (oldLevel != newLevel) {
f.set(svr, newLevel);
out.format(" New trace level: %s%n", f.get(svr));
}
// production code should handle these exceptions more gracefully
} catch (IllegalArgumentException x) {
x.printStackTrace();
} catch (IllegalAccessException x) {
x.printStackTrace();
} catch (NoSuchFieldException x) {
x.printStackTrace();
}
}
}
</source>



== Get declared methods for enum class ==



<source lang="java">

import java.lang.reflect.Method;
import org.xml.sax.XMLReader;
public class GetMethod {
public static void main(String[] args) {
Method[] ms = String.class.getMethods();
for (int i = 0; i < ms.length; i++) {
// System.out.println(ms[i].getName());
}
Method[] ims = XMLReader.class.getMethods();
for (int i = 0; i < ims.length; i++) {
// System.out.println(ims[i].getName());
}
Method[] sms = Size.class.getMethods();
for (int i = 0; i < sms.length; i++) {
// System.out.println(sms[i].getName());
}
String pc = new String();
try {
Method setCpu = String.class.getMethod("toString", String.class);
setCpu.invoke(pc, "Intel 3.0");
System.out.println(pc.toString());
} catch (Exception e) {
e.printStackTrace();
}
}
}
enum Size {
S, M, L, XL, XXL, XXXL;
}
</source>



== Is it an enum ==



<source lang="java">

import org.xml.sax.XMLReader;

public class IsEnum {
public static void main(String[] args) {
System.out.println(Size.class.isEnum());
System.out.println(String.class.isEnum());
System.out.println(String.class.isInstance("Test"));
System.out.println(XMLReader.class.isInterface());
}
}
enum Size {
S, M, L, XL, XXL, XXXL;
}
</source>

← Предыдущая	Версия 06:01, 1 июня 2010
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Java/Reflection/Enum - История изменений

Admin: 1 версия

в 18:01, 31 мая 2010