blocks|key|751449|text|可能v表指针的大小四舍五入为16的倍数。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|751450|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

Probably sizeof the v-table pointer rounded up to a multiple of 16.

blocks|key|2663686|text|该方法未以序列化形式存储。事情就是这么简单。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2663687|编辑：对于VM中的对象，在执行过程中，无论对象的类有多少个方法，大小都应该是恒定的。|offset|length|style|BOLD|2663688|entityMap^0|0|0|3|0^^$0|@$1|2|3|4|5|6|7|J|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|K|8|@$D|L|E|M|F|G]]|9|@]|A|$]]|$1|H|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|I|$]]

The method is not stored in the serialized form. It's as simple as that.

Edit: As for objects in the VM during execution, the size should be constant, regardless of how many methods the class of the object has.

blocks|key|2663693|text|80字节，因为对象中不包含方法。除非你也在谈论"vtable“类型的东西，在这种情况下可能有160个字节。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2663694|160个字节的说明。如果每个对象分配其自己的vtable+(这是一种可能的实现)，则将是160。或者(正如评论中指出的)，更好的方法是每个类一个vtable，这意味着指向vtable的指针大小为80+%2B(可能是4或8字节，具体取决于VM)。所以84或88个字节。|2663695|整个事情完全取决于VM分配内存和处理非最终方法的方式。如果不知道特定的VM是如何实现的，这两个问题都无法正确回答。|2663696|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|H|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|I|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|J|8|@]|9|@]|A|$]]|$1|F|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|G|$]]

80 bytes since a method is not included in the object. Unless you are also talking about the "vtable" type of thing, in which case probably 160 bytes. 

Clarification on the 160 bytes. The 160 would be if each object allocated its own vtable (which is one possible implementation). Alternatively (and as is pointed out in the comments) a better way would be one vtable per class, which would mean 80 + the size of the pointer to the vtable (probably 4 or 8 bytes depending on the VM). So 84 or 88 bytes.

This whole thing totally depends on the way the VM allocates memory and deals with non-final methods. Without knowing how the particular VM is implemented neither question can be answered correctly.

blocks|key|751480|text|等于80！(简而言之)|type|unstyled|depth|inlineStyleRanges|entityRanges|data|751481|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

blocks|key|758975|text|至少其他一些人已经说过，该方法不会存储在序列化中。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|758976|在此示例中，您可以使用以下代码轻松地执行一个测试来显示这一点。|758977|import+java.io.File;
import+java.io.FileOutputStream;
import+java.io.IOException;
import+java.io.ObjectOutputStream;
import+java.io.Serializable;


public+class+SerializationTest+{

++++public+static+void+main(String[]+args)+{
++++++++serialize(true);
++++++++serialize(false);
++++}

++++public+static+void+serialize(boolean+aOrB)+{
++++++++FileOutputStream+fos+=+null;
++++++++ObjectOutputStream+out+=+null;
++++++++try+{
++++++++++++fos+=+new+FileOutputStream("output.txt");
++++++++++++out+=+new+ObjectOutputStream(fos);
++++++++++++out.writeObject(aOrB+?+new+A()+:+new+B());
++++++++++++out.close();
++++++++++++fos.close();
++++++++}+catch+(IOException+ex)+{
++++++++++++ex.printStackTrace();
++++++++}
++++++++File+file+=+new+File("output.txt");
++++++++System.out.println(file.length());
++++}

++++public+static+class+A+implements+Serializable+{
++++++++int+a+=+0;
++++}

++++public+static+class+B+implements+Serializable+{
++++++++int+a+=+0;

++++++++public+int+foo(int+a)+{
++++++++++++return+a;
++++++++}
++++}
}|code-block|syntax|javascript|758978|对我来说，这是打印出来的|758979|48
48|758980|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|P|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|Q|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|R|8|@]|9|@]|A|$]]|$1|K|3|L|5|F|7|S|8|@]|9|@]|A|$G|H]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

As a few other people at least have said, the method is not stored in the serialization.

You can easily do a test to show this in this example with the following code.

<pre><code>import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectOutputStream;
import java.io.Serializable;


public class SerializationTest {

 public static void main(String[] args) {
 serialize(true);
 serialize(false);
 }

 public static void serialize(boolean aOrB) {
 FileOutputStream fos = null;
 ObjectOutputStream out = null;
 try {
 fos = new FileOutputStream("output.txt");
 out = new ObjectOutputStream(fos);
 out.writeObject(aOrB ? new A() : new B());
 out.close();
 fos.close();
 } catch (IOException ex) {
 ex.printStackTrace();
 }
 File file = new File("output.txt");
 System.out.println(file.length());
 }

 public static class A implements Serializable {
 int a = 0;
 }

 public static class B implements Serializable {
 int a = 0;

 public int foo(int a) {
 return a;
 }
 }
}
</code></pre>

For me this prints out

<pre><code>48
48
</code></pre>

blocks|key|2663728|text|开销是...没有。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2663729|方法定义和代码地址存储在Class对象中，它有一个唯一的实例，对象的每个实例都指向该实例。由于情况就是这样，无论是否添加了该方法，每个单独对象的开销都是零。|2663730|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

The overhead is... none.

The method definition and code address are stored in the Class object, which has a unique instance toward which every instance of your object points.
Since that would be the case, whether or not you added that method, the overhead for each individual object is nothing.

blocks|key|316055|text|对于32/64位JVM，这两种类型的对象都将使用大约20-24字节。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|316056|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

Objects of both classes will use about 20-24 bytes for 32/64-bit JVMs.

What is the memory overhead of a function in a class?

For example,

<pre><code>Class A
{
 int a
}

Class B
{
 int a
 int foo(int);
}
</code></pre>

So 100 instances of class A should be 80 bytes. What about 100 instances of class B?

What is the memory overhead of a Java method?

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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类中函数的内存开销是多少？例如,Class A{ int a}Class B{ int a int foo(int);}所以A类的100个实例应该是80个字节。那么B类的100个实例呢？

问Java方法的内存开销是多少？
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