home | O'Reilly's CD bookshelfs | FreeBSD | Linux | Cisco | Cisco Exam  

Java in a Nutshell

Previous Chapter 25
The java.lang Package

25.8 java.lang.Class (JDK 1.0)

This class represents a Java class or interface, or, in Java 1.1, any Java type. There is one Class object for each class that is loaded into the Java Virtual Machine, and in Java 1.1 there are special Class objects that represent the Java primitive types. The TYPE constants defined by Boolean, Integer, and the other primitive "wrapper classes" hold these special Class objects. Array types are also represented by Class objects in Java 1.1.

There is no constructor for this class. You can obtain a Class object by calling the getClass() method of any instance of the desired class. In Java 1.1, a Class object may also be referred to by appending .class to the name of a class. Finally, and most interestingly, a class can be dynamically loaded by passing its fully-qualified name (i.e., package name plus class name) to the static Class.forName() method. This method loads the named class, if it is not already loaded, into the Java interpreter, and returns a Class object for it.

The newInstance() method creates an instance of a given class--this allows you to create instances of dynamically loaded classes for which you cannot use the new keyword. Note that this method only works when the target class has a no-argument constructor. See newInstance() in java.lang.reflect.Constructor for a more powerful way to instantiate dynamically loaded classes.

getName() returns the name of the class. getSuperclass() returns its superclass. isInterface() tests whether the Class object represents an interface, and getInterfaces() returns an array of the interfaces that this class implements. The various other get and is methods return other information about the represented class, and form part of the Java Reflection API, along with the classes in java.lang.reflect.

public final class Class extends Object implements Serializable {
    // No Constructor
    // Class Methods
            public static native Class forName(String className) throws ClassNotFoundException;
    // Public Instance Methods
            public native ClassLoader getClassLoader();
        1.1public Class[] getClasses();
        1.1public native Class getComponentType();
        1.1public Constructor getConstructor(Class[] parameterTypes) throws NoSuchMethodException, SecurityException;
        1.1public Constructor[] getConstructors() throws SecurityException;
        1.1public Class[] getDeclaredClasses() throws SecurityException;
        1.1public Constructor getDeclaredConstructor(Class[] parameterTypes) throws NoSuchMethodException, SecurityException;
        1.1public Constructor[] getDeclaredConstructors() throws SecurityException;
        1.1public Field getDeclaredField(String name) throws NoSuchFieldException, SecurityException;
        1.1public Field[] getDeclaredFields() throws SecurityException;
        1.1public Method getDeclaredMethod(String name, Class[] parameterTypes) throws NoSuchMethodException, SecurityException;
        1.1public Method[] getDeclaredMethods() throws SecurityException;
        1.1public Class getDeclaringClass();
        1.1public Field getField(String name) throws NoSuchFieldException, SecurityException;
        1.1public Field[] getFields() throws SecurityException;
            public native Class[] getInterfaces();
        1.1public Method getMethod(String name, Class[] parameterTypes) throws NoSuchMethodException, SecurityException;
        1.1public Method[] getMethods() throws SecurityException;
        1.1public native int getModifiers();
            public native String getName();
        1.1public URL getResource(String name);
        1.1public InputStream getResourceAsStream(String name);
        1.1public native Object[] getSigners();
            public native Class getSuperclass();
        1.1public native boolean isArray();
        1.1public native boolean isAssignableFrom(Class cls);
        1.1public native boolean isInstance(Object obj);
            public native boolean isInterface();
        1.1public native boolean isPrimitive();
            public native Object newInstance() throws InstantiationException, IllegalAccessException;
            public String toString();  // Overrides Object

Passed To:

Array.newInstance(), BeanDescriptor(), Beans.getInstanceOf(), Beans.isInstanceOf(), Class.getConstructor(), Class.getDeclaredConstructor(), Class.getDeclaredMethod(), Class.getMethod(), Class.isAssignableFrom(), ClassLoader.resolveClass(), ClassLoader.setSigners(), Compiler.compileClass(), DataFlavor(), EventSetDescriptor(), IndexedPropertyDescriptor(), Introspector.getBeanInfo(), ObjectOutputStream.annotateClass(), ObjectStreamClass.lookup(), PropertyDescriptor(), PropertyDescriptor.setPropertyEditorClass(), PropertyEditorManager.findEditor(), PropertyEditorManager.registerEditor(), SecurityManager.checkMemberAccess()

Returned By:

BeanDescriptor.getBeanClass(), BeanDescriptor.getCustomizerClass(), Class.forName(), Class.getClasses(), Class.getComponentType(), Class.getDeclaredClasses(), Class.getDeclaringClass(), Class.getInterfaces(), Class.getSuperclass(), ClassLoader.defineClass(), ClassLoader.findLoadedClass(), ClassLoader.findSystemClass(), ClassLoader.loadClass(), Constructor.getDeclaringClass(), Constructor.getExceptionTypes(), Constructor.getParameterTypes(), DataFlavor.getRepresentationClass(), EventSetDescriptor.getListenerType(), Field.getDeclaringClass(), Field.getType(), IndexedPropertyDescriptor.getIndexedPropertyType(), Member.getDeclaringClass(), Method.getDeclaringClass(), Method.getExceptionTypes(), Method.getParameterTypes(), Method.getReturnType(), Object.getClass(), ObjectInputStream.resolveClass(), ObjectStreamClass.forClass(), PropertyDescriptor.getPropertyEditorClass(), PropertyDescriptor.getPropertyType(), SecurityManager.currentLoadedClass(), SecurityManager.getClassContext()

Type Of:

Boolean.TYPE, Byte.TYPE, Character.TYPE, Double.TYPE, Float.TYPE, Integer.TYPE, Long.TYPE, Short.TYPE, Void.TYPE

Previous Home Next
java.lang.Character (JDK 1.0) Book Index java.lang.ClassCastException (JDK 1.0)

Java in a Nutshell Java Language Reference Java AWT Java Fundamental Classes Exploring Java