Java reflection-call constructor and Operation Array

The two share a person class. Please refer to the code ..

The first is the demo of calling the constructor through Java reflection.

Package COM. jadyer. reflection; </P> <p> Import Java. lang. reflect. constructor; </P> <p>/** <br/> * reflection call constructor <br/> */<br/> public class invokeconstructor {<br/> Public static void main (string [] ARGs) throws exception {<br/> class <?> Clazz = Class. forname ("com. jadyer. model. person "); // create a class object, used to describe the person class </P> <p>/** <br/> * call the construction method with parameters <br/> */<br/> class <?> [] Argtypes = {string. Class, integer. Class}; // specifies the parameter of the constructor to be called. <br/> constructor <?> Constructor = clazz. getconstructor (argtypes); // obtain the constructor of a specified parameter. <br/> Object OBJ = constructor. newinstance ("Tomb stealing notes", 888); // creates an object based on the given real parameters. The returned value is the handle of the newly created object. <br/> system. out. println (OBJ); // print the newly created object. Here, tostring () is automatically called () output the values of the two attributes </P> <p>/** <br/> * call the construction method without parameters <br/> * @ see can also use the following two method, obtain the construction method without parameters <br/> * @ see constructor = clazz. getconstructor (new class [0]) <br/> * @ see constructor = clazz. getconstructor (null) <br/> * @ see. You can also use OBJ = clazz. newinstance () creates an object without a constructor <br/> */<br/> OBJ = clazz. getconstructor (). newinstance (); // obtain the construction method without parameters and use it to create an object <br/> system. out. println (OBJ); // print the attribute value of the newly created object. The tostring () method is still called automatically here <br/>}< br/>}

Then there is the shared person class.

Package COM. jadyer. model; </P> <p> public class person {<br/> Public string name; <br/> Public integer age; </P> <p> Public Person () {}</P> <p> Public Person (string name, integer age) {<br/> This. name = Name; <br/> This. age = age; <br/>}</P> <p> @ override <br/> Public String tostring () {<br/> return "Name: "+ name +"/Tage: "+ age; <br/>}< br/>}

Finally, the demo that uses Java reflection to operate Arrays

Package COM. jadyer. reflection; </P> <p> Import Java. lang. reflect. array; </P> <p> Import COM. jadyer. model. person; </P> <p>/** <br/> * array of reflection Operations <br/> */<br/> public class processarray {<br/> Public static void main (string [] ARGs) {<br/> int [] records = {89, 56, 43, 77, 33}; <br/> person [] persons = {new person ("Zhang qiling ", 26), new person ("Wang Zang Hai", 36), new person ("Tie bin Sheng", 46) }; <br/> records = (INT []) incrementarray (records ); <Br/> Persons = (person []) incrementarray (persons); </P> <p> List (records); // The five rows output here are zero, is the default initialization value of the expanded array <br/> system. out. println ("-------------------------------------"); </P> <p> List (persons); // The three rows output here are null, is the default initialization value of the expanded array <br/> system. out. println ("-------------------------------------"); </P> <p> int [] [] AA = (INT [] []) array. newinstance (Int. class, 2, 3); // create a multi-dimensional array and specify the element type and length of each dimension. <br/> system. out. println (AA ); <Br/>}</P> <p>/** <br/> * doubles the size of the specified array, at the same time, save the elements of the original array to the new array after expansion <br/> */<br/> Public static object incrementarray (Object array) {<br/> class <?> Elementtype = array. getclass (). getcomponenttype (); // obtain the type of the array element <br/> int size = array. getlength (array); // obtain the original size of the array <br/> Object newarray = array. newinstance (elementtype, size * 2); // creates an Array Based on the specified Element type and capacity. <br/> // system. arraycopy (array, 0, newarray, 0, size); // assign an array element. The following is a better description of the reflection mechanism <br/> for (INT I = 0; I <size; I ++) {// copy array elements <br/> Object OBJ = array. get (array, I); // gets the I-th element in the array, and returns the object type <br/> array. set (newarray, I, OBJ); // set the value of element I of the target array newarray to OBJ <br/>}< br/> return newarray; <br/>}</P> <p>/** <br/> * display all elements in the specified array <br/> */<br/> Public static void list (Object array) {<br/> int size = array. getlength (array); // obtain the length of the specified array object using the reflection API <br/> for (INT I = 0; I <size; I ++) {<br/> system. out. println (array. get (array, I); // output each element in the array <br/>}< br/>}