Reflection API provides us various methods to play around with array objects also. Refer below code demonstrating different array reflection methods.
newInstance() method in Array.java class helps us to create an array using reflection.
isArray() method on Class.java object represent whether the object is an array or not.
getComponentType() method on Class.java helps to identify the type of array.
get(<object_instance>, <index_number>) method fetch the value present at specified index number.
set(<object_instance>, <index_number>, <value>) method set the value at specified index number of the provided array instance.
import java.lang.reflect.Array;
import java.lang.reflect.Field;
public class FieldsAndArrays {
public static void main(String[] args) throws NoSuchFieldException, IllegalAccessException {
int[] inputArray = {10, 20, 30, 40};
inspectArray(inputArray);
updateArray(inputArray);
updateArray(new String("Not an array object"));
createArray();
FieldDemo fieldDemo = new FieldDemo();
setFieldValues(fieldDemo);
System.out.println("Values added through reflection :: " + fieldDemo.data);
}
public static void inspectArray(Object inputObject) {
Class<?> clazz = inputObject.getClass();
System.out.println("is array :: " + clazz.isArray() + " of type :: " + clazz.getComponentType().getName());
System.out.println("Length :: " + Array.getLength(inputObject));
System.out.println("Element at index 2 :: " + Array.get(inputObject, 2));
}
public static void updateArray(Object inputObject) {
Class<?> clazz = inputObject.getClass();
if (clazz.isArray()) {
Array.set(inputObject, 0, 100);
Array.set(inputObject, 1, 200);
Array.set(inputObject, 2, 300);
Array.set(inputObject, 3, 400);
printArray("Updated Array", inputObject, 4);
} else {
System.out.println("Input object is not an array");
}
}
public static void createArray() {
Object intArray = Array.newInstance(int.class, 3);
printArray("Reflection created array", intArray, 3);
}
static <T> T setFieldValues(T instance) throws NoSuchFieldException, IllegalAccessException {
Class<?> aClass = instance.getClass();
Field dataField = aClass.getDeclaredField("data");
dataField.setAccessible(true);
dataField.set(instance, 200);
return instance;
}
static void printArray(String refString, Object arrayObject, int arrayLength) {
int i = 0;
System.out.print(refString + " :: ");
while (i < arrayLength) {
System.out.print(Array.get(arrayObject, i) + " ");
i++;
}
System.out.println();
}
}
class FieldDemo {
int data;
}
