Constructor Reflection
Constructor provides information about a single constructor for a class.
Get the annotation declared for this constructor
<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.
Annotation[] getDeclaredAnnotations()- Returns all annotations that are directly present on this element.
Get the declaring class
Class<T> getDeclaringClass()- Returns the Class object representing the class that declares the constructor represented by this Constructor object.
Get the generic exception types
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.
Type[] getGenericExceptionTypes()- Returns an array of Type objects that represent the exceptions declared to be thrown by this Constructor object.
Get the generic parameter types
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.
Get the modifiers
int getModifiers()- Returns the Java language modifiers for the constructor represented by this Constructor object, as an integer.
Get the name of the contructor
String getName()- Returns the name of this constructor, as a string.
Get parameter's annotation, type
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.
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.
Get typed parameters
TypeVariable<Constructor<T>>[] getTypeParameters()- Returns an array of TypeVariable objects that represent the type variables declared by the generic declaration represented by this GenericDeclaration object, in declaration order.
Is this contructor a Synthetic, and does it have the variable number of arguments
boolean isSynthetic()- Returns true if this constructor is a synthetic constructor; returns false otherwise.
boolean isVarArgs()- Returns true if this constructor was declared to take a variable number of arguments; returns false otherwise.
Create new instance using the Contructor
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.
String representation of the contructor
String toGenericString()- Returns a string describing this Constructor, including type parameters.
String toString()- Returns a string describing this Constructor.
Revised from Open JDK source code
import java.lang.reflect.Constructor;
public class Main {
public static void main(String[] argv) throws Exception {
Constructor[] constructors = String.class.getDeclaredConstructors();
for (int i = 0; i < constructors.length; i++) {
Constructor c = constructors[i];
System.out.println(c.toGenericString());
}
}
}