java.lang.Object
java.lang.Class<T>
- All Implemented Interfaces:
- Serializable, AnnotatedElement, GenericDeclaration, Type
- See Also:
- Top Examples, Source Code,
ClassLoader.defineClass(byte[], int, int)
public <U> Class<? extends U> asSubclass(Class<U> clazz)
- See Also:
- ClassCastException
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public T cast(Object obj)
- See Also:
- ClassCastException
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public boolean desiredAssertionStatus()
- See Also:
ClassLoader.setDefaultAssertionStatus(boolean), ClassLoader.setPackageAssertionStatus(java.lang.String, boolean), ClassLoader.setClassAssertionStatus(java.lang.String, boolean)
- Geek's Notes:
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public static Class<?> forName(String className)
throws ClassNotFoundException- See Also:
- ExceptionInInitializerError, LinkageError
- Geek's Notes:
- Description Add your codes or notes Search More Java Examples
[265]Process DB records
By Anonymous on 2005/03/15 11:30:08 Rate
//Declare a method and some variables.
public void ListStudents ( ) throws SQLException {
int i, NoOfColumns;
String StNo,StFName,StLName;
//Initialize and load the JDBC-ODBC driver.
Class.forName ( "jdbc.odbc.JdbcOdbcDriver" ) ;
//Make the connection object.
Connection Ex1Con = DriverManager.getConnection ( "jdbc:odbc:StudentDB;uid="admin";pw="sa" ) ;
//Create a simple Statement object.
Statement Ex1Stmt = Ex1Con.createStatement ( ) ;
//Make a SQL string, pass it to the DBMS, and execute the SQL statement.
ResultSet Ex1rs = Ex1Stmt.executeQuery ( "SELECT StudentNumber, FirstName, LastName FROM Students" ) ;
//Process each row until there are no more rows.
// Displays the results on the console.
System.out.println ( "Student Number First Name Last Name" ) ;
while ( Ex1rs.next ( ) ) {
// Get the column values into Java variables
StNo = Ex1rs.getString ( 1 ) ;
StFName = Ex1rs.getString ( 2 ) ;
StLName = Ex1rs.getString ( 3 ) ;
System.out.println ( StNo,StFName,StLName ) ;
}
} [926]Better way to load class
By Anonymous on 2004/09/25 22:10:03 Rate
It is better to do:
Thread.getContextClassLoader ( ) .loadClass ( "Foo" ) ;
Than:
Class.forName ( "foo" ) ;
This is why,
Class.forName will use the ClassLoader for the current class. Whereas
the other uses the classloader associated with the current thread.
The problem is that you usually want to load classes in the thread's
classloader because it "knows what's going on" better.
For example, you write code in a jar and put it in the app server's
shared library location. You have a web application that calls into it with the name of a class you want to load that is defined in a jar in WEB-INF/lib. If you use Class.forName, it will fail, whereas with
Thread one should succeed.
The same thing potentially could happen with shared jars in an ear and
other situations.
[1304]Alternative way to load class
By Anonymous on 2005/02/15 03:58:24 Rate
Another alternative is:
Class.forName ( "Foo", true, ClassLoader.getSystemClassLoader ( ) )
This behaves more like Class.forName, e.g. throws same exceptions, and has some advantages and disadvantages compared to:
Thread.getContextClassLoader ( ) .loadClass ( "Foo" )
Both are better than:
Class.forName ( "Foo" )
See:
http://www.theserverside.com/articles/content/dm_classForname/DynLoad.pdf
for a discussion of this issue.[1946]What is the difference between Class.forName() and ClassLoader.loadClass()?
By Anonymous on 2007/12/07 13:50:52 Rate
Both methods try to dynamically locate and load a java.lang.Class object corresponding to a given class name. However, their behavior differs regarding which java.lang.ClassLoader they use for class loading and whether or not the resulting Class object is initialized.
The most common form of Class.forName ( ) , the one that takes a single String parameter, always uses the caller's classloader. This is the classloader that loads the code executing the forName ( ) method. By comparison, ClassLoader.loadClass ( ) is an instance method and requires you to select a particular classloader, which may or may not be the loader that loads that calling code. If picking a specific loader to load the class is important to your design, you should use ClassLoader.loadClass ( ) or the three-parameter version of forName ( ) added in Java 2 Platform, Standard Edition ( J2SE ) : Class.forName ( String, boolean, ClassLoader ) .
Additionally, Class.forName ( ) 's common form initializes the loaded class. The visible effect of this is the execution of the class's static initializers as well as byte code corresponding to initialization expressions of all static fields ( this process occurs recursively for all the class's superclasses ) . This differs from ClassLoader.loadClass ( ) behavior, which delays initialization until the class is used for the first time.
You can take advantage of the above behavioral differences. For example, if you are about to load a class you know has a very costly static initializer, you may choose to go ahead and load it to ensure it is found in the classpath but delay its initialization until the first time you need to make use of a field or method from this particular class.
The three-parameter method Class.forName ( String, boolean, ClassLoader ) is the most general of them all. You can delay initialization by setting the second parameter to false and pick a given classloader using the third parameter. I recommend always using this method for maximum flexibility.
public static Class<?> forName(String name,
boolean initialize,
ClassLoader loader)
throws ClassNotFoundException- See Also:
-
forName(String), ExceptionInInitializerError, LinkageError
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public <A extends Annotation> A getAnnotation(Class<A> annotationClass)
- See Also:
- AnnotatedElement
- Geek's Notes:
- Description Add your codes or notes Search More Java Examples
public Annotation[] getAnnotations()
- See Also:
- AnnotatedElement
- Geek's Notes:
- Description Add your codes or notes Search More Java Examples
public String getCanonicalName()
- Geek's Notes:
- Description Add your codes or notes Search More Java Examples
public Class[] getClasses()
- See Also:
s.checkPackageAccess(), s.checkMemberAccess(this, Member.PUBLIC), SecurityException
- Geek's Notes:
- Description Add your codes or notes Search More Java Examples
public ClassLoader getClassLoader()
- See Also:
RuntimePermission, SecurityManager.checkPermission(java.security.Permission), SecurityException
- Geek's Notes:
- Description Add your codes or notes Search More Java Examples
public Class<?> getComponentType()
- See Also:
Array
- Geek's Notes:
- Description Add your codes or notes Search More Java Examples
public Constructor<T> getConstructor(Class... parameterTypes)
throws NoSuchMethodException,
SecurityException- See Also:
s.checkPackageAccess(), s.checkMemberAccess(this, Member.PUBLIC)
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- Description Add your codes or notes Search More Java Examples
public Constructor getConstructor(Class[] parameterTypes)
throws NoSuchMethodException,
SecurityException- See Also:
SecurityManager.checkPackageAccess(String), SecurityManager.checkMemberAccess(Class, int)
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- Description Add your codes or notes Search More Java Examples
[44]Look for the constructor that has one String parameter
By Anonymous on 2005/02/22 10:52:02 Rate
Class cl = null;
Constructor cnst = null;
cl = getClass ( ) .forName ( "MyClass" ) ;
//Look for the constructor that has one String parameter
cnst = cl.getConstructor ( new Class [ ] { String.class } ) ;
MyClass mc = ( MyClass ) cnst.newInstance ( new Object [ ] { "A String" } ) ;
public Constructor[] getConstructors()
throws SecurityException- See Also:
s.checkPackageAccess(), s.checkMemberAccess(this, Member.PUBLIC)
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public Annotation[] getDeclaredAnnotations()
- See Also:
- AnnotatedElement
- Geek's Notes:
- Description Add your codes or notes Search More Java Examples
public Class[] getDeclaredClasses()
throws SecurityException- See Also:
s.checkPackageAccess(), s.checkMemberAccess(this, Member.DECLARED)
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- Description Add your codes or notes Search More Java Examples
public Constructor<T> getDeclaredConstructor(Class... parameterTypes)
throws NoSuchMethodException,
SecurityException- See Also:
s.checkPackageAccess(), s.checkMemberAccess(this, Member.DECLARED)
- Geek's Notes:
- Description Add your codes or notes Search More Java Examples
public Constructor getDeclaredConstructor(Class[] parameterTypes)
throws NoSuchMethodException,
SecurityException- See Also:
SecurityManager.checkPackageAccess(String), SecurityManager.checkMemberAccess(Class, int)
- Geek's Notes:
- Description Add your codes or notes Search More Java Examples
public Constructor[] getDeclaredConstructors()
throws SecurityException- See Also:
s.checkPackageAccess(), s.checkMemberAccess(this, Member.DECLARED)
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- Description Add your codes or notes Search More Java Examples
public Field getDeclaredField(String name)
throws NoSuchFieldException,
SecurityException- See Also:
s.checkPackageAccess(), s.checkMemberAccess(this, Member.DECLARED), NullPointerException
- Geek's Notes:
- Description Add your codes or notes Search More Java Examples
public Field[] getDeclaredFields()
throws SecurityException- See Also:
s.checkPackageAccess(), s.checkMemberAccess(this, Member.DECLARED)
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public Method getDeclaredMethod(String name,
Class... parameterTypes)
throws NoSuchMethodException,
SecurityException- See Also:
s.checkPackageAccess(), s.checkMemberAccess(this, Member.DECLARED), NullPointerException
- Geek's Notes:
- Description Add your codes or notes Search More Java Examples
public Method getDeclaredMethod(String name,
Class[] parameterTypes)
throws NoSuchMethodException,
SecurityException- See Also:
SecurityManager.checkPackageAccess(String), SecurityManager.checkMemberAccess(Class, int)
- Geek's Notes:
- Description Add your codes or notes Search More Java Examples
public Method[] getDeclaredMethods()
throws SecurityException- See Also:
s.checkPackageAccess(), s.checkMemberAccess(this, Member.DECLARED)
- Geek's Notes:
- Description Add your codes or notes Search More Java Examples
public Class<?> getDeclaringClass()
- Geek's Notes:
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[1246]getDeclaringClass V. getEnclosingClass
By howard { dot } lovatt { at } iee { dot } org on 2005/01/06 17:20:28 Rate
The subtilty with this method is that anonymous inner classes are not counted as member of a class in the Java Language Specification whereas named inner classes are. Therefore this method returns null for an anonymous class. The alternative method getEnclosingClass works for both anonymous and named classes.
public Class<?> getEnclosingClass()
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[1247]_
By howard { dot } lovatt { at } iee { dot } org on 2005/01/06 17:22:23 Rate
The difference between this method and getDeclaringClass is explained under getDeclaringClass.
public Constructor<?> getEnclosingConstructor()
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public Method getEnclosingMethod()
- Geek's Notes:
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public T[] getEnumConstants()
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public Field getField(String name)
throws NoSuchFieldException,
SecurityException- See Also:
s.checkPackageAccess(), s.checkMemberAccess(this, Member.PUBLIC), NullPointerException
- Geek's Notes:
- Description Add your codes or notes Search More Java Examples
[140]Class getField
By natali { dot } roiz { at } nsi { dot } co { dot } il on 2003/01/06 04:08:37 Rate
CallEventRecordManipulator.class.getField ( outputObj ) =
( Class.forName ( OutputTypeName ) ) data.get ( "OutputRec" ) ;
public Field[] getFields()
throws SecurityException- See Also:
s.checkPackageAccess(), s.checkMemberAccess(this, Member.PUBLIC)
- Geek's Notes:
- Description Add your codes or notes Search More Java Examples
public Type[] getGenericInterfaces()
- See Also:
- TypeNotPresentException,
ParameterizedType
- Geek's Notes:
- Description Add your codes or notes Search More Java Examples
public Type getGenericSuperclass()
- See Also:
- TypeNotPresentException,
ParameterizedType
- Geek's Notes:
- Description Add your codes or notes Search More Java Examples
public Class[] getInterfaces()
- Geek's Notes:
- Description Add your codes or notes Search More Java Examples
public Method getMethod(String name,
Class... parameterTypes)
throws NoSuchMethodException,
SecurityException- See Also:
s.checkPackageAccess(), s.checkMemberAccess(this, Member.PUBLIC), NullPointerException
- Geek's Notes:
- Description Add your codes or notes Search More Java Examples
[1521]Passing correct parameter data type
By Mikko Ohtamaa on 2005/08/23 06:42:30 Rate
// For primitive parameters, use primitive.class type,
// no Integer.class for example
Class [ ] parameters;
if ( value instanceof Boolean ) {
parameters = new Class [ ] { boolean.class } ;
} else {
parameters = new Class [ ] { value.getClass ( ) } ;
}
m = dataSource.getClass ( ) .getMethod ( methodName, parameters ) ;[1938]Example for use invoke method and getMethod
By kaman on 2007/11/01 05:27:55 Rate
public class MainClass {
public static void main ( String [ ] args ) throws Exception {
Method method = Text.class.getMethod ( "sayHello", null ) ;
method.invoke ( new Text ( ) ) ;
}
}
class Text {
public void sayHello ( ) {
System.out.println ( "Hello World" ) ;
}
}
public Method getMethod(String name,
Class[] parameterTypes)
throws NoSuchMethodException,
SecurityException- See Also:
SecurityManager.checkPackageAccess(String), SecurityManager.checkMemberAccess(Class, int)
- Geek's Notes:
- Description Add your codes or notes Search More Java Examples
public Method[] getMethods()
throws SecurityException- See Also:
s.checkPackageAccess(), s.checkMemberAccess(this, Member.PUBLIC)
- Geek's Notes:
- Description Add your codes or notes Search More Java Examples
public int getModifiers()
- See Also:
Modifier
- Geek's Notes:
- Description Add your codes or notes Search More Java Examples
public String getName()
- Geek's Notes:
- Description Add your codes or notes Search More Java Examples
public Package getPackage()
- Geek's Notes:
- Description Add your codes or notes Search More Java Examples
public ProtectionDomain getProtectionDomain()
- See Also:
RuntimePermission, SecurityManager.checkPermission(java.security.Permission), SecurityException
- Geek's Notes:
- Description Add your codes or notes Search More Java Examples
public URL getResource(String name)
- See Also:
-
ClassLoader.getSystemResource(java.lang.String)
- Geek's Notes:
- Description Add your codes or notes Search More Java Examples
[1413]Determine the names of the files in a directory associated with a class
By Anonymous on 2005/05/04 18:50:17 Rate
//determine the names of the files in a directory
//associated with a class.
String directory = ....;
URL url = MyClass.class.getResource ( directory ) ;
File file = new File ( new URI ( url.toString ( ) ) ) ;
String [ ] list = file.list ( ) ;
public InputStream getResourceAsStream(String name)
- See Also:
- NullPointerException,
ClassLoader.getSystemResourceAsStream(java.lang.String)
- Geek's Notes:
- Description Add your codes or notes Search More Java Examples
[963]Two ways to opening a file from the class path
By Anonymous on 2004/10/01 14:37:20 Rate
Both Class and Classloader have a method getResourceAsStream ( String ) for opening a file from the class path.
public Object[] getSigners()
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public String getSimpleName()
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public Class<? super T> getSuperclass()
- Geek's Notes:
- Description Add your codes or notes Search More Java Examples
public TypeVariable<Class<T>>[] getTypeParameters()
- See Also:
- GenericDeclaration
- Geek's Notes:
- Description Add your codes or notes Search More Java Examples
public boolean isAnnotation()
- See Also:
isInterface()
- Geek's Notes:
- Description Add your codes or notes Search More Java Examples
public boolean isAnnotationPresent(Class<? extends Annotation> annotationClass)
- See Also:
- AnnotatedElement
- Geek's Notes:
- Description Add your codes or notes Search More Java Examples
public boolean isAnonymousClass()
- Geek's Notes:
- Description Add your codes or notes Search More Java Examples
public boolean isArray()
- Geek's Notes:
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[1896]possible alternative
By John Newman on 2007/06/29 14:24:01 Rate
this method is kind of slow,
object.getClass ( ) .getName ( ) .charAt ( 0 ) == ' [ '
may work just as well. Can anyone think of any cases it would miss or return a false positive?
It is much faster!! I am not sure what isArray ( ) really does ( native ) , but it is slow & this is orders of magnitude faster. So far I think it works fine.
public boolean isAssignableFrom(Class<?> cls)
- See Also:
- NullPointerException
- Geek's Notes:
- Description Add your codes or notes Search More Java Examples
public boolean isEnum()
- Geek's Notes:
- Description Add your codes or notes Search More Java Examples
public boolean isInstance(Object obj)
- Geek's Notes:
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public boolean isInterface()
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public boolean isLocalClass()
- Geek's Notes:
- Description Add your codes or notes Search More Java Examples
public boolean isMemberClass()
- Geek's Notes:
- Description Add your codes or notes Search More Java Examples
public boolean isPrimitive()
- See Also:
Void.TYPE, Double.TYPE, Float.TYPE, Long.TYPE, Integer.TYPE, Short.TYPE, Byte.TYPE, Character.TYPE, Boolean.TYPE
- Geek's Notes:
- Description Add your codes or notes Search More Java Examples
public boolean isSynthetic()
- Geek's Notes:
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public T newInstance()
throws InstantiationException,
IllegalAccessException- See Also:
s.checkPackageAccess(), s.checkMemberAccess(this, Member.PUBLIC), SecurityException, ExceptionInInitializerError, InvocationTargetException, Constructor.newInstance
- Geek's Notes:
- Description Add your codes or notes Search More Java Examples
public String toString()
- See Also:
- Object
- Geek's Notes:
- Description Add your codes or notes Search More Java Examples
Java API By Example, From Geeks To Geeks.