Java and the exact reference size for objects, arrays, and primitive types

I would like to know exactly the real space allocated in memory for an object.

I will try to explain in the following example: using a 64-bit JVM, the size of the pointer should be 8 bytes, therefore:

• Object singletest = new Object(); will take 8 bytes to refer to the object plus the size of the object
  
• Object arraytest = new Object[10]; will take 8 bytes to refer to the position where the array is stored, plus 8 * 10 bytes to store the array plus the size of each object
  
• int singleint = new int; takes only 2 bytes, because int is a primitive type
• int[] arrayint = new int[10]; will take 8 bytes for position reference and 10 * 2 bytes for elements
  

In addition, it is for this reason that Java allows you to write code as follows:

int[][] doublearray = new int[2][];
int[0][] = new int[5];
int[1][] = new int[10];

, , (aka pointer), , ( , ). : doublearray (8 ), - , 8 * 2 ( ) , , 2 * 5 2 * 10.

, , :

class Test {
   int a, b;
   int getA() {return A};
   void setA(int a) {this.a = a;}
   int getB() {return B};
   void setB(int b) {this.b = b;}
}

, ( , Java) 8 2 + 2 .

: , ? , , , 8 ? , ?

, , ( "int i", ++, , ​​ "0" ).

... , , ! (, , , )