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我编写了一些代码来确定各种数据结构占用的内存。我使用classmexer api 来获取深/浅内存。我尝试了使用内部类节点实现的自定义整数堆栈上的调用。（我正在运行这个上ubuntu lucid）

对于空栈，浅内存和深内存都是 16 字节对于 4 个整数的堆栈，深内存是 176 字节。这个数字让我很困惑，因为手动计算内存如下

4 个整数的堆栈：

object overhead = 16 bytes
reference to Node inst variable = 8
primitive type int variable = 4
padding = 4
total = 32

Each entry in stack has
Node = 40 bytes(inner class)
Integer field = 24 
total = 64

所以，应该是 32+64N

对于 N = 4，这将是 288

那么，为什么 classmexer 将内存使用情况显示为 176 ？

还有一件事..我如何确定machine word size我的系统。我查看了 lang.System 类，但找不到任何 api

这是我的代码

public class MemoryUsage {
    private static void linkedListMemUsage(){
        StackOfIntegers si1 = new StackOfIntegers();

        long deepmem = MemoryUtil.deepMemoryUsageOf(si1);
        long shallowmem = MemoryUtil.memoryUsageOf(si1);

        System.out.println("\nfor an empty stack of integers");
        System.out.println("*******************************");
        System.out.println(si1.getClass().getSimpleName()+" took deep:"+deepmem+" bytes");
        System.out.println(si1.getClass().getSimpleName()+" took shallow:"+shallowmem+" bytes");

        StackOfIntegers si2 = new StackOfIntegers();
        si2.push(new Integer(100));
        si2.push(new Integer(200));
        si2.push(new Integer(300));
        si2.push(new Integer(400));

        deepmem = MemoryUtil.deepMemoryUsageOf(si2);
        shallowmem = MemoryUtil.memoryUsageOf(si2);

        System.out.println("\nfor a stack of 4 integers");
        System.out.println("*************************");
        System.out.println(si1.getClass().getSimpleName()+" took deep:"+deepmem+" bytes");
        System.out.println(si1.getClass().getSimpleName()+" took shallow:"+shallowmem+" bytes");


    }
    public static void main(String[] args) {
        linkedListMemUsage();
    }
    class StackOfIntegers{
        private int N;
        private Node first;

        public void push(Integer item){
        Node old = first;
        first = new Node();
        first.item = item;
        first.next = old;
        N++;
        }
        private class Node{
            Integer item;
            Node next;
        }
    }
}
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