struct - Can't instantiate structure inside structure in java -

my aim create data structure should have following representation in memory:

    int    countofelements; // 4 bytes     int    time_1;          // 4 bytes     double price_1;         // 8 bytes     int    time_2;          // 4 bytes     double price_2;         // 8 bytes     int    time_3;          // 4 bytes     double price_3;         // 8 bytes      . . . . .     int    time_n;          // 4 bytes, n = countofelements     double price_n;         // 8 bytes, n = countofelements 

unfortunately, not free choose representation (field order , type) of structure in memory, because relates process on os. data structure intended placed on shared memory using winapi functions, , purpose of data structure data exchange. thus, i'll needed pointer data structure in java... so, effort realize data structure looks like:

import java.util.list; import java.util.arrays; import com.sun.jna.structure;  public class tquote extends structure {     public int    time;     public double price;      @override     protected list getfieldorder() {         return arrays.aslist(new string[]{"time", "price"});     } }  public class tsharedarray extends structure {     public int      countofelements;     public tquote[] elements;      public tsharedarray(int size) {         super();         countofelements = size;         elements = new tquote[size];         (int = 0; < size; i++) elements[i] = new tquote();     }      @override     protected list getfieldorder() {         return arrays.aslist(new string[]{"countofelements", "elements"});     } } 

though, attempts instantiate structure tsharedarray structure = new tsharedarray(10); throws exception:

/*  invalid structure field in class xxx$tsharedarray, field name 'elements' (class xxx$tquote): can't instantiate class xxx$tquote (java.lang.instantiationexception: xxx$tquote)     java.lang.illegalargumentexception: invalid structure field in class xxx$tsharedarray, field name 'elements' (class xxx$tquote): can't instantiate class xxx$tquote (java.lang.instantiationexception: xxx$tquote)         @ com.sun.jna.structure.validatefield(structure.java:962)         @ com.sun.jna.structure.validatefield(structure.java:954)         @ com.sun.jna.structure.validatefields(structure.java:972)         @ com.sun.jna.structure.<init>(structure.java:186)         @ com.sun.jna.structure.<init>(structure.java:180)         @ com.sun.jna.structure.<init>(structure.java:167)         @ com.sun.jna.structure.<init>(structure.java:159)         @ xxx$tsharedarray.<init>(xxx.java:35)         @ xxx.onstart(xxx.java:57)         @ java.lang.thread.run(unknown source) */ 

java code in xxx.java line #35 super(); ideas, how fix it?

additionally, noticed 1 strange thing... let's assume, have 3 structures , each of these structures contains of 2 fields:

public class tintint extends structure {     public int int1;     public int int2;      @override     protected list getfieldorder() {       return arrays.aslist(new string[]{"int1", "int2"});     } }  public class tdbldbl extends structure {     public double dbl1;     public double dbl2;      @override     protected list getfieldorder() {       return arrays.aslist(new string[]{"dbl1", "dbl2"});     } }  public class tintdbl extends structure {     public int    int1;     public double dbl1;      @override     protected list getfieldorder() {       return arrays.aslist(new string[]{"int1", "dbl1"});     } } 

the first 1 (tintint) have size expected of 2*4=8 bytes, second 1 (tdbldbl) have size expected of 2*8=16 bytes, third (tintdbl - it's same tquote) have size of 16 bytes instead of expected of 4+8=12. why?:

system.out.println("tintint.size()=" + new tintint().size()); //  8 bytes, ok system.out.println("tdbldbl.size()=" + new tdbldbl().size()); // 16 bytes, ok system.out.println("tintdbl.size()=" + new tintdbl().size()); // 16 bytes!!! why? 

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the amount of memory used increased in 8 byte blocks. more details see https://stackoverflow.com/a/321436/3915166