Category: javareflect

java.lang.reflect – Constructor<T> Class ”; Previous Next Introduction The java.lang.reflect.Constructor class provides information about, and access to, a single constructor for a class. Constructor permits widening conversions to occur when matching the actual parameters to newInstance() with the underlying constructor”s formal parameters, but throws an IllegalArgumentException if a narrowing conversion would occur. Class declaration Following is the declaration for java.lang.reflect.Constructor class − public final class Constructor<T> extends AccessibleObject implements GenericDeclaration, Member Class methods Sr.No. Method & Description 1 boolean equals(Object obj) Compares this Constructor against the specified object. 2 <T extends Annotation> T getAnnotation(Class<T> annotationClass) Returns this element”s annotation for the specified type if such an annotation is present, else null. 3 Annotation[] getDeclaredAnnotations() Returns all annotations that are directly present on this element. 4 Class<T> getDeclaringClass() Returns the Class object representing the class that declares the constructor represented by this Constructor object. 5 Class<?>[] getExceptionTypes() Returns an array of Class objects that represent the types of exceptions declared to be thrown by the underlying constructor represented by this Constructor object. 6 Type[] getGenericExceptionTypes() Returns an array of Type objects that represent the exceptions declared to be thrown by this Constructor object. 7 Type[] getGenericParameterTypes() Returns an array of Type objects that represent the formal parameter types, in declaration order, of the method represented by this Constructor object. 8 int getModifiers() Returns the Java language modifiers for the constructor represented by this Constructor object, as an integer. 9 String getName() Returns the name of this constructor, as a string. 10 Annotation[][] getParameterAnnotations() Returns an array of arrays that represent the annotations on the formal parameters, in declaration order, of the method represented by this Constructor object. 11 Class<?>[] getParameterTypes() Returns an array of Class objects that represent the formal parameter types, in declaration order, of the constructor represented by this Constructor object. 12 int hashCode() Returns a hashcode for this Constructor. 13 boolean isSynthetic() Returns true if this constructor is a synthetic constructor; returns false otherwise. 14 boolean isVarArgs() Returns true if this constructor was declared to take a variable number of arguments; returns false otherwise. 15 T newInstance(Object… initargs) Uses the constructor represented by this Constructor object to create and initialize a new instance of the constructor”s declaring class, with the specified initialization parameters. 16 String toGenericString() Returns a string describing this Constructor, including type parameters. 17 String toString() Returns a string describing this Constructor. Methods inherited This class inherits methods from the following classes − java.lang.reflect.AccessibleObject java.lang.Object Print Page Previous Next Advertisements ”;

java.lang.reflect – AccessibleObject Class ”; Previous Next Introduction The java.lang.reflect.AccessibleObject class is the base class for Field, Method and Constructor objects. It provides the ability to flag a reflected object as suppressing default Java language access control checks when it is used. The access checks for public, default (package) access, protected, and private members are performed when Fields, Methods or Constructors are used to set or get fields, to invoke methods, or to create and initialize new instances of classes, respectively. Setting the accessible flag in a reflected object permits sophisticated applications with sufficient privilege, such as Java Object Serialization or other persistence mechanisms, to manipulate objects in a manner that would normally be prohibited. Class declaration Following is the declaration for java.lang.reflect.AccessibleObject class − public class AccessibleObject extends Object implements AnnotatedElement Constructors Sr.No. Constructor & Description 1 protected AccessibleObject() Constructor: only used by the Java Virtual Machine. Class methods Sr.No. Method & Description 1 <T extends Annotation> T getAnnotation(Class<T> annotationClass) Returns this element”s annotation for the specified type if such an annotation is present, else null. 2 Annotation[] getAnnotations() Returns all annotations present on this element. 3 Annotation[] getDeclaredAnnotations() Returns all annotations that are directly present on this element. 4 boolean isAccessible() Get the value of the accessible flag for this object. 5 boolean isAnnotationPresent(Class<? extends Annotation> annotationClass) Returns true if an annotation for the specified type is present on this element, else false. 6 static void setAccessible(AccessibleObject[] array, boolean flag) Convenience method to set the accessible flag for an array of objects with a single security check (for efficiency). 7 void setAccessible(boolean flag) Set the accessible flag for this object to the indicated boolean value. Methods inherited This class inherits methods from the following classes − java.lang.Object Print Page Previous Next Advertisements ”;

java.lang.reflect – Method Class ”; Previous Next Introduction The java.lang.reflect.Method class provides information about, and access to, a single method on a class or interface. The reflected method may be a class method or an instance method (including an abstract method). A Method permits widening conversions to occur when matching the actual parameters to invoke with the underlying method”s formal parameters, but it throws an IllegalArgumentException if a narrowing conversion would occur. Class declaration Following is the declaration for java.lang.reflect.Method class − public final class Method<T> extends AccessibleObject implements GenericDeclaration, Member Class methods Sr.No. Method & Description 1 boolean equals(Object obj) Compares this Method against the specified object. 2 <T extends Annotation> T getAnnotation(Class<T> annotationClass) Returns this element”s annotation for the specified type if such an annotation is present, else null. 3 Annotation[] getDeclaredAnnotations() Returns all annotations that are directly present on this element. 4 Class<T> getDeclaringClass() Returns the Class object representing the class that declares the method represented by this Method object. 5 Object getDefaultValue() Returns the default value for the annotation member represented by this Method instance. 6 Class<?>[] getExceptionTypes() Returns an array of Class objects that represent the types of exceptions declared to be thrown by the underlying constructor represented by this Constructor object. 7 Type[] getGenericExceptionTypes() Returns an array of Type objects that represent the exceptions declared to be thrown by this Constructor object. 8 Type[] getGenericParameterTypes() Returns an array of Type objects that represent the formal parameter types, in declaration order, of the method represented by this Constructor object. 9 Type getGenericReturnType() Returns a Type object that represents the formal return type of the method represented by this Method object. 10 int getModifiers() Returns the Java language modifiers for the method represented by this Method object, as an integer. 11 String getName() Returns the name of this method, as a string. 12 Annotation[][] getParameterAnnotations() Returns an array of arrays that represent the annotations on the formal parameters, in declaration order, of the method represented by this Method object. 13 Class<?>[] getParameterTypes() Returns an array of Class objects that represent the formal parameter types, in declaration order, of the constructor represented by this Method object. 14 Class<?> getReturnType() Returns a Class object that represents the formal return type of the method represented by this Method object. 15 int hashCode() Returns a hashcode for this Constructor. 16 Object invoke(Object obj, Object… args) Invokes the underlying method represented by this Method object, on the specified object with the specified parameters. 17 boolean isBridge() Returns true if this method is a bridge method; returns false otherwise. 18 boolean isSynthetic() Returns true if this method is a synthetic method; returns false otherwise. 19 boolean isVarArgs() Returns true if this method was declared to take a variable number of arguments; returns false otherwise. 20 String toGenericString() Returns a string describing this Method, including type parameters. 21 String toString() Returns a string describing this Method. Methods inherited This class inherits methods from the following classes − java.lang.reflect.AccessibleObject java.lang.Object Print Page Previous Next Advertisements ”;

java.lang.reflect – Useful Resources ”; Previous Next The following resources contain additional information on JAVA. Please use them to get more in-depth knowledge on this topic. Useful Links on Java The JavaTM Tutorials − The Java Tutorials are practical guides for programmers who want to use the Java programming language to create applications. JavaTM 2 SDK, Standard Edition − Official site for JavaTM 2 SDK, Standard Edition Free Java Download − Download Java for your desktop computer now! Sun Developer Network − Sun Microsystem”s official website listing down all the API documentation, latest Java Technologies, Books and other resource. Useful Books on Java To enlist your site on this page, please drop an email to [email protected] Print Page Previous Next Advertisements ”;

java.lang.reflect – Quick Guide ”; Previous Next java.lang.reflect – AccessibleObject Class Introduction The java.lang.reflect.AccessibleObject class is the base class for Field, Method and Constructor objects. It provides the ability to flag a reflected object as suppressing default Java language access control checks when it is used. The access checks for public, default (package) access, protected, and private members are performed when Fields, Methods or Constructors are used to set or get fields, to invoke methods, or to create and initialize new instances of classes, respectively. Setting the accessible flag in a reflected object permits sophisticated applications with sufficient privilege, such as Java Object Serialization or other persistence mechanisms, to manipulate objects in a manner that would normally be prohibited. Class declaration Following is the declaration for java.lang.reflect.AccessibleObject class − public class AccessibleObject extends Object implements AnnotatedElement Constructors Sr.No. Constructor & Description 1 protected AccessibleObject() Constructor: only used by the Java Virtual Machine. Class methods Sr.No. Method & Description 1 <T extends Annotation> T getAnnotation(Class<T> annotationClass) Returns this element”s annotation for the specified type if such an annotation is present, else null. 2 Annotation[] getAnnotations() Returns all annotations present on this element. 3 Annotation[] getDeclaredAnnotations() Returns all annotations that are directly present on this element. 4 boolean isAccessible() Get the value of the accessible flag for this object. 5 boolean isAnnotationPresent(Class<? extends Annotation> annotationClass) Returns true if an annotation for the specified type is present on this element, else false. 6 static void setAccessible(AccessibleObject[] array, boolean flag) Convenience method to set the accessible flag for an array of objects with a single security check (for efficiency). 7 void setAccessible(boolean flag) Set the accessible flag for this object to the indicated boolean value. Methods inherited This class inherits methods from the following classes − java.lang.Object java.lang.reflect – Array Class Introduction The java.lang.reflect.Array class provides static methods to dynamically create and access Java arrays. Array permits widening conversions to occur during a get or set operation, but throws an IllegalArgumentException if a narrowing conversion would occur. Class declaration Following is the declaration for java.lang.reflect.Array class − public final class Array extends Object Class methods Sr.No. Method & Description 1 static Object get(Object array, int index) Returns the value of the indexed component in the specified array object. 2 static boolean getBoolean(Object array, int index) Returns the value of the indexed component in the specified array object, as a boolean. 3 static byte getByte(Object array, int index) Returns the value of the indexed component in the specified array object, as a byte. 4 static char getChar(Object array, int index) Returns the value of the indexed component in the specified array object, as a char. 5 static double getDouble(Object array, int index) Returns the value of the indexed component in the specified array object, as a double. 6 static float getFloat(Object array, int index) Returns the value of the indexed component in the specified array object, as a float. 7 static int getInt(Object array, int index) Returns the value of the indexed component in the specified array object, as an int. 8 static int getLength(Object array) Returns the length of the specified array object, as an int. 9 static long getLong(Object array, int index) Returns the value of the indexed component in the specified array object, as a long. 10 static short getShort(Object array, int index) Returns the value of the indexed component in the specified array object, as a short. 11 static Object newInstance(Class<?> componentType, int… dimensions) Creates a new array with the specified component type and dimensions. 12 static Object newInstance(Class<?> componentType, int length) Creates a new array with the specified component type and length. 13 static void set(Object array, int index, Object value) Sets the value of the indexed component of the specified array object to the specified new value. 14 static void setBoolean(Object array, int index, boolean z) Sets the value of the indexed component of the specified array object to the specified boolean value. 15 static void setByte(Object array, int index, byte b) Sets the value of the indexed component of the specified array object to the specified byte value. 16 static void setChar(Object array, int index, char c) Sets the value of the indexed component of the specified array object to the specified char value. 17 static void setDouble(Object array, int index, double d) Sets the value of the indexed component of the specified array object to the specified double value. 18 static void setFloat(Object array, int index, float f) Sets the value of the indexed component of the specified array object to the specified float value. 19 static void setInt(Object array, int index, int i) Sets the value of the indexed component of the specified array object to the specified int value. 20 static void setLong(Object array, int index, long l) Sets the value of the indexed component of the specified array object to the specified long value. 21 static void setShort(Object array, int index, short s) Sets the value of the indexed component of the specified array object to the specified short value. Methods inherited This class inherits methods from the following classes − java.lang.Object java.lang.reflect – Constructor<T> Class Introduction The java.lang.reflect.Constructor class provides information about, and access to, a single constructor for a class. Constructor permits widening conversions to occur when matching the actual parameters to newInstance() with the underlying constructor”s formal parameters, but throws an IllegalArgumentException if a narrowing conversion would occur. Class declaration Following is the declaration for java.lang.reflect.Constructor class − public final class Constructor<T> extends AccessibleObject implements GenericDeclaration, Member Class methods Sr.No. Method & Description 1 boolean equals(Object obj) Compares this Constructor against the specified object. 2 <T extends Annotation> T getAnnotation(Class<T> annotationClass) Returns this element”s annotation for the specified type if such an annotation is present, else null. 3 Annotation[] getDeclaredAnnotations() Returns all annotations that are directly present on this element. 4 Class<T> getDeclaringClass() Returns the Class object representing the class that declares the constructor represented by this Constructor object. 5 Class<?>[] getExceptionTypes() Returns an array of Class

Discuss java.lang.reflect ”; Previous Next java.lang.reflect package provides classes and interfaces which are used to obtain reflective information about classes and objects. Reflection API allows programmatic access to information about the fields, methods and constructors of loaded classes. It allows use of reflected fields, methods, and constructors to operate on their underlying counterparts, within security restrictions. This reference will take you through simple and practical methods available in java.lang.reflect package. Print Page Previous Next Advertisements ”;

java.lang.reflect – Proxy Class ”; Previous Next Introduction The java.lang.reflect.Proxy class provides static methods for creating dynamic proxy classes and instances, and it is also the superclass of all dynamic proxy classes created by those methods. Class declaration Following is the declaration for java.lang.reflect.Proxy class − public class Proxy extends Object implements Serializable Fields Following are the fields for java.lang.reflect.Proxy class − protected InvocationHandler h − the invocation handler for this proxy instance. Constructors Sr.No. Constructor & Description 1 protected Proxy(InvocationHandler h) Constructs a new Proxy instance from a subclass (typically, a dynamic proxy class) with the specified value for its invocation handler. Class methods Sr.No. Method & Description 1 static InvocationHandler getInvocationHandler(Object proxy) Returns the invocation handler for the specified proxy instance. 2 static Class<?> getProxyClass(ClassLoader loader, Class<?>… interfaces) Returns the java.lang.Class object for a proxy class given a class loader and an array of interfaces. 3 static boolean isProxyClass(Class<?> cl) Returns true if and only if the specified class was dynamically generated to be a proxy class using the getProxyClass method or the newProxyInstance method. 4 static Object newProxyInstance(ClassLoader loader, Class<?>[] interfaces, InvocationHandler h) Returns an instance of a proxy class for the specified interfaces that dispatches method invocations to the specified invocation handler. Methods inherited This class inherits methods from the following classes − java.lang.Object Print Page Previous Next Advertisements ”;

java.lang.reflect – Interfaces ”; Previous Next Introduction The java.lang.reflect Interfaces contains the interfaces which are used to obtain reflective information about classes and objects. Interface Summary Sr.No. Interface & Description 1 AnnotatedElement Represents an annotated element of the program currently running in this VM. 2 GenericArrayType GenericArrayType represents an array type whose component type is either a parameterized type or a type variable. 3 GenericDeclaration A common interface for all entities that declare type variables. 4 InvocationHandler InvocationHandler is the interface implemented by the invocation handler of a proxy instance. 5 Member Member is an interface that reflects identifying information about a single member (a field or a method) or a constructor. 6 ParameterizedType ParameterizedType represents a parameterized type such as Collection<String>. 7 Type Type is the common superinterface for all types in the Java programming language. 8 List<E> This is an ordered collection (also known as a sequence). 9 TypeVariable<D extends GenericDeclaration> TypeVariable is the common superinterface for type variables of kinds. 10 WildcardType WildcardType represents a wildcard type expression, such as ?, ? extends Number, or ? super Integer. Print Page Previous Next Advertisements ”;

java.lang.reflect – Exceptions ”; Previous Next Introduction The java.lang.reflect Exceptions contains the exceptions which can occur during reflection operations. Exceptions Summary Sr.No. Exception & Description 1 InvocationTargetException InvocationTargetException is a checked exception that wraps an exception thrown by an invoked method or constructor. 2 MalformedParameterizedTypeException Thrown when a semantically malformed parameterized type is encountered by a reflective method that needs to instantiate it. 3 UndeclaredThrowableException Thrown by a method invocation on a proxy instance if its invocation handler”s invoke method throws a checked exception (a Throwable that is not assignable to RuntimeException or Error) that is not assignable to any of the exception types declared in the throws clause of the method that was invoked on the proxy instance and dispatched to the invocation handler. Print Page Previous Next Advertisements ”;

java.lang.reflect – Modifier Class ”; Previous Next Introduction The java.lang.reflect.Modifier class provides static methods and constants to decode class and member access modifiers. The sets of modifiers are represented as integers with distinct bit positions representing different modifiers. The values for the constants representing the modifiers are taken from the tables in sections 4.1, 4.4, 4.5, and 4.7 of The Java Virtual Machine Specification. Class declaration Following is the declaration for java.lang.reflect.Modifier class − public class Modifier extends Object Fields Following are the fields for java.lang.reflect.Modifier class − static int ABSTRACT − The int value representing the abstract modifier. static int FINAL − The int value representing the final modifier. static int INTERFACE − The int value representing the interface modifier. static int NATIVE − The int value representing the native modifier. static int PRIVATE − The int value representing the private modifier. static int PROTECTED − The int value representing the protected modifier. static int PUBLIC − The int value representing the public modifier. static int STATIC − The int value representing the static modifier. static int STRICT − The int value representing the strictfp modifier. static int SYNCHRONIZED − The int value representing the synchronized modifier. static int TRANSIENT − The int value representing the transient modifier. static int VOLATILE − The int value representing the volatile modifier. Constructors Sr.No. Constructor & Description 1 Modifier() Default Constructor. Class methods Sr.No. Method & Description 1 static int classModifiers() Return an int value OR-ing together the source language modifiers that can be applied to a class. 2 static int constructorModifiers() Return an int value OR-ing together the source language modifiers that can be applied to a constructor. 3 static int fieldModifiers() Return an int value OR-ing together the source language modifiers that can be applied to a field. 4 static int interfaceModifiers() Return an int value OR-ing together the source language modifiers that can be applied to an interface. 5 static boolean isAbstract(int mod) Return true if the integer argument includes the abstract modifier, false otherwise. 6 static boolean isFinal(int mod) Return true if the integer argument includes the final modifier, false otherwise. 7 static boolean isInterface(int mod) Return true if the integer argument includes the interface modifier, false otherwise. 8 static boolean isNative(int mod) Return true if the integer argument includes the native modifier, false otherwise. 9 static boolean isPrivate(int mod) Return true if the integer argument includes the private modifier, false otherwise. 10 static boolean isProtected(int mod) Return true if the integer argument includes the protected modifier, false otherwise. 11 static boolean isPublic(int mod) Return true if the integer argument includes the public modifier, false otherwise. 12 static boolean isStatic(int mod) Return true if the integer argument includes the static modifier, false otherwise. 13 static boolean isStrict(int mod) Return true if the integer argument includes the strictfp modifier, false otherwise. 14 static boolean isSynchronized(int mod) Return true if the integer argument includes the synchronized modifier, false otherwise. 15 static boolean isTransient(int mod) Return true if the integer argument includes the transient modifier, false otherwise. 16 static boolean isVolatile(int mod) Return true if the integer argument includes the volatile modifier, false otherwise. 17 static int methodModifiers() Return an int value OR-ing together the source language modifiers that can be applied to a method. 18 static String toString(int mod) Return a string describing the access modifier flags in the specified modifier. Methods inherited This class inherits methods from the following classes − java.lang.Object Print Page Previous Next Advertisements ”;