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Java Collection Q&A » array » reflection 

1. Java array reflection: isArray vs. instanceof

Is there a preference or behavior difference between using:

if(obj.getClass().isArray()) {}
if(obj instanceof Object[]) {}

2. Java Reflection isArray() always false

Hey anyone, I got a question about Java Reflections: I have to checkout, if a certain field of a class is an array. But my problem is: If i run isArray() on the ...

3. Invoke method accepting multiple arguments with arguments array

I need to invoke a method without knowing a priori what will the amount of arguments be.
I've tried using the member Method.invoke(Object, Object...) passing as second parameter an array of objects ...

4. Java Beans: Overglorified Associative Arrays?

I don't understand the nature of Java Beans that well. Well, at least how I see them used in some code-bases that pass through our shop. I found this question: The accepted ...

5. Can Variable number of variables with incremental variableNames be created through reflection in Java?

Hi I have the following requirement. I want to create variable number of String arrays in a method, based on the number of levels present. For e.g I have the variable numOfLevels (int) received ...

6. How to get the array type given the array member type using reflection in Java

I have a Class variable that holds a certain type and I need to get a variable that holds the corresponding Array type. The best I could come up with is ...

7. Multi-Dimension length array reflection java

How do I find the length of a multi-dimensional array with reflection on java?

8. Java: Setting array length for an unknown number of entries

I am trying to fill a RealVector (from Apache Commons Math) with values. I tried using the class's append method, but that didn't actually add anything. So now I'm ...

9. How to 'getConstructor' where constructor signature contains java array

Is it possible to use getConstructor to obtain the constructor of the class X below?

public class A {

public class Y {


public class X extends Y {
    public X(A ...

10. Iterating over arrays by reflection

I am doing some reflection work and go to a little problem. I am trying to print objects to some GUI tree and have problem detecting arrays in a generic way. I suggested ...

11. Matching Class arrays

I'm writing a routine to invoke methods, found by a name and an array of parameter Class values Matching the Method by getName works, but when trying to match the given Class[] ...

12. Why Use java.lang.reflect.Array For Anything Other Than Array Creation?

Java Class java.lang.reflect.Array provides a set of tools for creating an array dynamically. However in addition to that it has a whole set of methods for accessing (get, ...

13. How do I iterate over an Array field reflectively?

I have

Class<? extends Object> class1 = obj.getClass();
    Field[] fields = class1.getDeclaredFields();
    for (Field aField : fields) {

14. Java casting Arrays

I wrote a simple library in which the user extends one of my abstract classes and then passes that class to one of my functions.

//user class
class My_robot extends Robot{

//My library function
function ...

15. Getting the array Class of a given class

Given a Class<?> that describes class A, is it somehow possible to get the Class<?> that matches the class A[]?

Class<?> clazz = A.class;
Class<?> arrayclazz = clazz.toArray(); // ??

assert arrayclazz.equals(A[].class);

16. getTypeParameters returns a null TypeVariable array

I am writing a program that displays the methods inside a Class along with it's access modifier, return type and parameters. Here's my code

import java.lang.reflect.*;
class RefTest1{

    public static void ...

17. Problem with constructing class using reflection and array arguments

running the folowing code:

    public class Test {
    public Test(Object[] test){


    public static void main(String[] args) throws Exception{

18. Reflection overload. Populating reflected array for reflected varargs method

I'm in the middle of a contender for the greatest kludge of all time. I need to use Spring JDBC without ever making reference to it. A custom classloader is providing ...

19. Get the code name of a Class

I'm doing some code generation using reflection and need to get the string describing certain array types in code. The default API doesn't really make this easy.

  • (new int[12]).getClass().getName() returns [I
  • (new Date[2][]).getClass().getName() ...

20. How to know if method is taking array as param using reflection

I am trying to invoke the API with the given input parameters. Input params are coming as a List. Now my job is get the API's parameter types one by one ...

21. Why am I getting an emtpy array of annotations here

According to the doc and to this answer I shuold be having "Override" ( or something similar ) in the following code:

import java.lang.reflect.*;
import java.util.*;
import static java.lang.System.out;
class Test { ...

22. How can I get the Array field of a class with reflection?

My class A has

   AClaz[] rofl;
The documentation for getDeclaredFields says "This method returns an array of length 0 if the class or interface declares no fields, or if this ...

23. java java.lang.reflect.Array.getLength vs array.getLength

I've got to maintain some code written by someone else who is no longer with the company. I'm seeing several references to java.lang.reflect.Array.getLength(anArray). Its working, but I've never seen ...

24. Unpacking an Array using reflection

I am trying to unpack an array I obtain from reflecting an objects fields. I set the value of the general field to an Object. If it is an Array I then ...

25. Reflecting an array in Java

I am new in Java and have a task to write some application. Faced one problem which can not pass :( The issue is to update an array element through reflection (app ...

26. Passing an array into a vararg method (in Reflection API)

I don't believe it's the call to getDeclaredMethod() that's the problem -- I believe it's the call to invoke(), where the underlying method wants an Object[] (an array of arguments) and you're passing a String[], which is itself an Object[], and it is being misinterpreted as the list of arguments itself, rather than as a single element of that list. You'd ...

27. calling a method in a method array (reflection api stuff)

Im not quite sure I follow what you've said. Should I make an object out of the method I want to call like this (example)? Class c = classLoader.loadClass("testClass"); Method[] cMethods = c.getMethods(); Object methodObj = cMethods[1]; invoke(methodObj, null); this gives me the compiler error: [20:1] cannot resolve symbol symbol : method invoke (java.lang.Object, location: class fileloader2 invoke(methodObj, null); ^ ...

28. Reflection: Reading an array field

Hi All, I am using Reflection (java 1.4.2) to read an object and display its instance variables and the values they hold. I am facing a problem with reading instance variables of type array. The difficulty is explained below: if( field.getType().isArray() ) { Objecy obj = field.getObj(); //The obj can be an array of a primitive or any //reference type. Now, ...

29. Array reflection in Java

Hey, using reflections is considered a hint for a bad architecture of your program, so unless there is good reason and you really know what you're doing, don't use it. If you can't help it and still have to use reflections: The getClass() method of Object provide useful method you might want to check into.

30. Arrays and Reflection?

31. How do I find an Array size in reflection

I may not have made myself clear (then again, I may have). I would like to determine the array size from a Class or Field object, not from an array object. That is: class Able { class NotAble { int ary = new int[20]; } public void method() { Class c = NotAble.class; Field[] f = c.getDeclaredFields(); // Now, how do ...  | Contact Us | Privacy Policy
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