在Java中，确定对象大小的最佳方法是什么？
我有一个应用程序，它读取一个包含成堆数据行的CSV文件。我会根据数据类型向用户提供行数的摘要，但我希望确保不会读入太多的数据行，从而导致在Java中，确定对象大小的最佳方法是什么？,java,memory,Java,Memory,我有一个应用程序，它读取一个包含成堆数据行的CSV文件。我会根据数据类型向用户提供行数的摘要，但我希望确保不会读入太多的数据行，从而导致OutOfMemoryErrors。每行转换为一个对象。有没有一种简单的方法可以通过编程方式确定该对象的大小？是否有一个引用定义了VM的基元类型和对象引用的大小 现在，我有一个代码，上面写着最多读取32000行，但我也希望有一个代码，上面写着在使用32MB内存之前，尽可能多地读取行。也许这是一个不同的问题，但我还是想知道 我怀疑您是否希望以编程方式执行此操作，除
OutOfMemoryErrorVM现在，我有一个代码，上面写着最多读取32000行，但我也希望有一个代码，上面写着在使用32MB内存之前，尽可能多地读取行。也许这是一个不同的问题，但我还是想知道 我怀疑您是否希望以编程方式执行此操作，除非您只想执行一次并将其存储以备将来使用。这是一件昂贵的事情。Java中没有sizeof（）操作符，即使有，它也只计算对其他对象的引用的成本和原语的大小 一种方法是将内容序列化为文件，并查看文件大小，如下所示：
Serializable myObject;
ObjectOutputStream oos = new ObjectOutputStream (new FileOutputStream ("obj.ser"));
oos.write (myObject);
oos.close ();
// Get current size of heap in bytes
long heapSize = Runtime.getRuntime().totalMemory();
// Get maximum size of heap in bytes. The heap cannot grow beyond this size.
// Any attempt will result in an OutOfMemoryException.
long heapMaxSize = Runtime.getRuntime().maxMemory();
// Get amount of free memory within the heap in bytes. This size will increase
// after garbage collection and decrease as new objects are created.
long heapFreeSize = Runtime.getRuntime().freeMemory();
另一种策略是获取每个对象并通过反射检查其成员，然后将大小相加（boolean&byte=1字节，short&char=2字节，等等），沿着成员资格层次结构进行操作。但是，这既繁琐又昂贵，并且最终会做与序列化策略相同的事情。我怀疑您是否希望以编程方式进行此操作，除非您只想执行一次并将其存储以供将来使用。这是一件昂贵的事情。Java中没有sizeof（）操作符，即使有，它也只计算对其他对象的引用的成本和原语的大小 一种方法是将内容序列化为文件，并查看文件大小，如下所示：
Serializable myObject;
ObjectOutputStream oos = new ObjectOutputStream (new FileOutputStream ("obj.ser"));
oos.write (myObject);
oos.close ();
// Get current size of heap in bytes
long heapSize = Runtime.getRuntime().totalMemory();
// Get maximum size of heap in bytes. The heap cannot grow beyond this size.
// Any attempt will result in an OutOfMemoryException.
long heapMaxSize = Runtime.getRuntime().maxMemory();
// Get amount of free memory within the heap in bytes. This size will increase
// after garbage collection and decrease as new objects are created.
long heapFreeSize = Runtime.getRuntime().freeMemory();
另一种策略是获取每个对象并通过反射检查其成员，然后将大小相加（boolean&byte=1字节，short&char=2字节，等等），沿着成员资格层次结构进行操作。但是这样做既繁琐又昂贵，并且最终会做与序列化策略相同的事情。如果您需要的话，没有方法调用。只要稍加研究，我想你可以自己写。一个特定的实例具有一个固定的大小，该大小是由引用数和原语值加上实例簿记数据派生的。您可以简单地遍历对象图。行类型的变化越小，就越容易
如果这样做太慢或者麻烦太多，那么总有一个很好的老式行计数规则。如果你要求的是方法调用，那么就没有方法调用。只要稍加研究，我想你可以自己写。一个特定的实例具有一个固定的大小，该大小是由引用数和原语值加上实例簿记数据派生的。您可以简单地遍历对象图。行类型的变化越小，就越容易
如果这太慢或者麻烦太多，那么总是有一个很好的老式的拇指行计数规则。如果您只想知道JVM中使用了多少内存，有多少是空闲的，您可以尝试以下方法：
Serializable myObject;
ObjectOutputStream oos = new ObjectOutputStream (new FileOutputStream ("obj.ser"));
oos.write (myObject);
oos.close ();
// Get current size of heap in bytes
long heapSize = Runtime.getRuntime().totalMemory();
// Get maximum size of heap in bytes. The heap cannot grow beyond this size.
// Any attempt will result in an OutOfMemoryException.
long heapMaxSize = Runtime.getRuntime().maxMemory();
// Get amount of free memory within the heap in bytes. This size will increase
// after garbage collection and decrease as new objects are created.
long heapFreeSize = Runtime.getRuntime().freeMemory();
编辑：我认为这可能会有所帮助，因为问题作者还表示，他希望拥有处理“在使用32MB内存之前读取尽可能多的行”的逻辑。如果您只想知道JVM中使用了多少内存，有多少是可用的，您可以尝试以下方法：
Serializable myObject;
ObjectOutputStream oos = new ObjectOutputStream (new FileOutputStream ("obj.ser"));
oos.write (myObject);
oos.close ();
// Get current size of heap in bytes
long heapSize = Runtime.getRuntime().totalMemory();
// Get maximum size of heap in bytes. The heap cannot grow beyond this size.
// Any attempt will result in an OutOfMemoryException.
long heapMaxSize = Runtime.getRuntime().maxMemory();
// Get amount of free memory within the heap in bytes. This size will increase
// after garbage collection and decrease as new objects are created.
long heapFreeSize = Runtime.getRuntime().freeMemory();
编辑：我认为这可能会有所帮助，因为问题作者还表示，他希望有一种逻辑能够处理“在使用32MB内存之前尽可能多地读取行”。您必须使用反射来漫游对象。你要小心：
- 仅仅分配一个对象在JVM中会有一些开销。数量因JVM而异，因此可以将此值作为参数。至少将其设置为常量（8字节？），并应用于分配的任何内容
- 仅仅因为
理论上是1字节并不意味着它只需要内存中的一个字节byte - 对象引用中将有循环，因此您需要保留一个
或类似的东西，使用objectequals作为比较器来消除无限循环HashMap
@jodonnell：我喜欢你的解决方案的简单性，但是很多对象是不可序列化的（因此这会引发异常），字段可以是暂时的，对象可以覆盖标准方法。你必须使用反射遍历对象。你要小心：
- 仅仅分配一个对象在JVM中会有一些开销。数量因JVM而异，因此可以将此值作为参数。至少将其设置为常量（8字节？），并应用于分配的任何内容
- 仅仅因为
理论上是1字节并不意味着它只需要内存中的一个字节byte - 对象引用中将有循环，因此您需要保留一个
或类似的东西，使用objectequals作为比较器来消除无限循环HashMap
@jodonnell：我喜欢您的解决方案的简单性，但许多对象是不可序列化的（因此这会引发异常），字段可能是暂时的，对象可以覆盖标准方法。您必须使用工具测量它，或者手动估计它，这取决于您使用的JVM 每个对象都有一些固定的开销。它是特定于JVM的，但我通常估计为40字节。然后你要看看这个班的成员。对象引用是32位（64位）JVM中的4（8）个字节。基本类型包括：<
public class Test1 {
// non-static nested
class Nested { }
// static nested
static class StaticNested { }
static long getFreeMemory () {
// waits for free memory measurement to stabilize
long init = Runtime.getRuntime().freeMemory(), init2;
int count = 0;
do {
System.out.println("waiting..." + init);
System.gc();
try { Thread.sleep(250); } catch (Exception x) { }
init2 = init;
init = Runtime.getRuntime().freeMemory();
if (init == init2) ++ count; else count = 0;
} while (count < 5);
System.out.println("ok..." + init);
return init;
}
Test1 () throws InterruptedException {
Object[] s = new Object[10000];
Object[] n = new Object[10000];
Object[] t = new Object[10000];
long init = getFreeMemory();
//for (int j = 0; j < 10000; ++ j)
// s[j] = new Separate();
long afters = getFreeMemory();
for (int j = 0; j < 10000; ++ j)
n[j] = new Nested();
long aftersn = getFreeMemory();
for (int j = 0; j < 10000; ++ j)
t[j] = new StaticNested();
long aftersnt = getFreeMemory();
System.out.println("separate: " + -(afters - init) + " each=" + -(afters - init) / 10000);
System.out.println("nested: " + -(aftersn - afters) + " each=" + -(aftersn - afters) / 10000);
System.out.println("static nested: " + -(aftersnt - aftersn) + " each=" + -(aftersnt - aftersn) / 10000);
}
public static void main (String[] args) throws InterruptedException {
new Test1();
}
}
nested: 160000 each=16
static nested: 160000 each=16
long heapSizeBefore = Runtime.getRuntime().totalMemory();
// Code for object construction
...
long heapSizeAfter = Runtime.getRuntime().totalMemory();
long size = heapSizeAfter - heapSizeBefore;
import java.lang.reflect.Array;
import java.lang.reflect.Field;
import java.lang.reflect.Modifier;
import java.util.IdentityHashMap;
import java.util.Stack;
import sun.misc.Unsafe;
/** Usage:
* MemoryUtil.sizeOf( object )
* MemoryUtil.deepSizeOf( object )
* MemoryUtil.ADDRESS_MODE
*/
public class MemoryUtil
{
private MemoryUtil()
{
}
public static enum AddressMode
{
/** Unknown address mode. Size calculations may be unreliable. */
UNKNOWN,
/** 32-bit address mode using 32-bit references. */
MEM_32BIT,
/** 64-bit address mode using 64-bit references. */
MEM_64BIT,
/** 64-bit address mode using 32-bit compressed references. */
MEM_64BIT_COMPRESSED_OOPS
}
/** The detected runtime address mode. */
public static final AddressMode ADDRESS_MODE;
private static final Unsafe UNSAFE;
private static final long ADDRESS_SIZE; // The size in bytes of a native pointer: 4 for 32 bit, 8 for 64 bit
private static final long REFERENCE_SIZE; // The size of a Java reference: 4 for 32 bit, 4 for 64 bit compressed oops, 8 for 64 bit
private static final long OBJECT_BASE_SIZE; // The minimum size of an Object: 8 for 32 bit, 12 for 64 bit compressed oops, 16 for 64 bit
private static final long OBJECT_ALIGNMENT = 8;
/** Use the offset of a known field to determine the minimum size of an object. */
private static final Object HELPER_OBJECT = new Object() { byte b; };
static
{
try
{
// Use reflection to get a reference to the 'Unsafe' object.
Field f = Unsafe.class.getDeclaredField( "theUnsafe" );
f.setAccessible( true );
UNSAFE = (Unsafe) f.get( null );
OBJECT_BASE_SIZE = UNSAFE.objectFieldOffset( HELPER_OBJECT.getClass().getDeclaredField( "b" ) );
ADDRESS_SIZE = UNSAFE.addressSize();
REFERENCE_SIZE = UNSAFE.arrayIndexScale( Object[].class );
if( ADDRESS_SIZE == 4 )
{
ADDRESS_MODE = AddressMode.MEM_32BIT;
}
else if( ADDRESS_SIZE == 8 && REFERENCE_SIZE == 8 )
{
ADDRESS_MODE = AddressMode.MEM_64BIT;
}
else if( ADDRESS_SIZE == 8 && REFERENCE_SIZE == 4 )
{
ADDRESS_MODE = AddressMode.MEM_64BIT_COMPRESSED_OOPS;
}
else
{
ADDRESS_MODE = AddressMode.UNKNOWN;
}
}
catch( Exception e )
{
throw new Error( e );
}
}
/** Return the size of the object excluding any referenced objects. */
public static long shallowSizeOf( final Object object )
{
Class<?> objectClass = object.getClass();
if( objectClass.isArray() )
{
// Array size is base offset + length * element size
long size = UNSAFE.arrayBaseOffset( objectClass )
+ UNSAFE.arrayIndexScale( objectClass ) * Array.getLength( object );
return padSize( size );
}
else
{
// Object size is the largest field offset padded out to 8 bytes
long size = OBJECT_BASE_SIZE;
do
{
for( Field field : objectClass.getDeclaredFields() )
{
if( (field.getModifiers() & Modifier.STATIC) == 0 )
{
long offset = UNSAFE.objectFieldOffset( field );
if( offset >= size )
{
size = offset + 1; // Field size is between 1 and PAD_SIZE bytes. Padding will round up to padding size.
}
}
}
objectClass = objectClass.getSuperclass();
}
while( objectClass != null );
return padSize( size );
}
}
private static final long padSize( final long size )
{
return (size + (OBJECT_ALIGNMENT - 1)) & ~(OBJECT_ALIGNMENT - 1);
}
/** Return the size of the object including any referenced objects. */
public static long deepSizeOf( final Object object )
{
IdentityHashMap<Object,Object> visited = new IdentityHashMap<Object,Object>();
Stack<Object> stack = new Stack<Object>();
if( object != null ) stack.push( object );
long size = 0;
while( !stack.isEmpty() )
{
size += internalSizeOf( stack.pop(), stack, visited );
}
return size;
}
private static long internalSizeOf( final Object object, final Stack<Object> stack, final IdentityHashMap<Object,Object> visited )
{
// Scan for object references and add to stack
Class<?> c = object.getClass();
if( c.isArray() && !c.getComponentType().isPrimitive() )
{
// Add unseen array elements to stack
for( int i = Array.getLength( object ) - 1; i >= 0; i-- )
{
Object val = Array.get( object, i );
if( val != null && visited.put( val, val ) == null )
{
stack.add( val );
}
}
}
else
{
// Add unseen object references to the stack
for( ; c != null; c = c.getSuperclass() )
{
for( Field field : c.getDeclaredFields() )
{
if( (field.getModifiers() & Modifier.STATIC) == 0
&& !field.getType().isPrimitive() )
{
field.setAccessible( true );
try
{
Object val = field.get( object );
if( val != null && visited.put( val, val ) == null )
{
stack.add( val );
}
}
catch( IllegalArgumentException e )
{
throw new RuntimeException( e );
}
catch( IllegalAccessException e )
{
throw new RuntimeException( e );
}
}
}
}
}
return shallowSizeOf( object );
}
}
import java.io.ByteArrayOutputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
public class ObjectSizeCalculator {
private Object getFirstObjectReference(Object o) {
String objectType = o.getClass().getTypeName();
if (objectType.substring(objectType.length()-2).equals("[]")) {
try {
if (objectType.equals("java.lang.Object[]"))
return ((Object[])o)[0];
else if (objectType.equals("int[]"))
return ((int[])o)[0];
else
throw new RuntimeException("Not Implemented !");
} catch (IndexOutOfBoundsException e) {
return null;
}
}
return o;
}
public int getObjectSizeInBytes(Object o) {
final String STRING_JAVA_TYPE_NAME = "java.lang.String";
if (o == null)
return 0;
String objectType = o.getClass().getTypeName();
boolean isArray = objectType.substring(objectType.length()-2).equals("[]");
Object objRef = getFirstObjectReference(o);
if (objRef != null && !(objRef instanceof Serializable))
throw new RuntimeException("Object must be serializable for measuring it's memory footprint using this method !");
try {
ByteArrayOutputStream baos = new ByteArrayOutputStream();
ObjectOutputStream oos = new ObjectOutputStream(baos);
oos.writeObject(o);
oos.close();
byte[] bytes = baos.toByteArray();
for (int i = bytes.length - 1, j = 0; i != 0; i--, j++) {
if (objectType != STRING_JAVA_TYPE_NAME) {
if (bytes[i] == 112)
if (isArray)
return j - 4;
else
return j;
} else {
if (bytes[i] == 0)
return j - 1;
}
}
} catch (Exception e) {
return -1;
}
return -1;
}
}
int [] intArray = new int [1]; will require 4 bytes.
long [] longArray = new long [1]; will require 8 bytes.
Object[] objectArray = new Object[1]; will require 4 bytes. The object can be any user defined Object.
Long [] longArray = new Long [1]; will require 4 bytes.
class ReferenceMemoryTest {
public String refStr;
public Object refObj;
public Double refDoub;
}
new MemoryMeter().measureDeep(myHashMap);
System.gc();
Runtime.getRuntime().totalMemory() - Runtime.getRuntime().freeMemory();
do your job here
System.gc();
Runtime.getRuntime().totalMemory() - Runtime.getRuntime().freeMemory();
Running 64-bit HotSpot VM.
Using compressed oop with 0-bit shift.
Using compressed klass with 3-bit shift.
Objects are 8 bytes aligned.
Field sizes by type: 4, 1, 1, 2, 2, 4, 4, 8, 8 [bytes]
Array element sizes: 4, 1, 1, 2, 2, 4, 4, 8, 8 [bytes]
java.util.regex.Pattern object internals:
OFFSET SIZE TYPE DESCRIPTION VALUE
0 4 (object header) 01 00 00 00 (0000 0001 0000 0000 0000 0000 0000 0000)
4 4 (object header) 00 00 00 00 (0000 0000 0000 0000 0000 0000 0000 0000)
8 4 (object header) cb cf 00 20 (1100 1011 1100 1111 0000 0000 0010 0000)
12 4 int Pattern.flags 0
16 4 int Pattern.capturingGroupCount 1
20 4 int Pattern.localCount 0
24 4 int Pattern.cursor 48
28 4 int Pattern.patternLength 0
32 1 boolean Pattern.compiled true
33 1 boolean Pattern.hasSupplementary false
34 2 (alignment/padding gap) N/A
36 4 String Pattern.pattern (object)
40 4 String Pattern.normalizedPattern (object)
44 4 Node Pattern.root (object)
48 4 Node Pattern.matchRoot (object)
52 4 int[] Pattern.buffer null
56 4 Map Pattern.namedGroups null
60 4 GroupHead[] Pattern.groupNodes null
64 4 int[] Pattern.temp null
68 4 (loss due to the next object alignment)
Instance size: 72 bytes (reported by Instrumentation API)
Space losses: 2 bytes internal + 4 bytes external = 6 bytes total
java.util.regex.Pattern instance footprint:
COUNT AVG SUM DESCRIPTION
1 112 112 [C
3 272 816 [Z
1 24 24 java.lang.String
1 72 72 java.util.regex.Pattern
9 24 216 java.util.regex.Pattern$1
13 24 312 java.util.regex.Pattern$5
1 16 16 java.util.regex.Pattern$Begin
3 24 72 java.util.regex.Pattern$BitClass
3 32 96 java.util.regex.Pattern$Curly
1 24 24 java.util.regex.Pattern$Dollar
1 16 16 java.util.regex.Pattern$LastNode
1 16 16 java.util.regex.Pattern$Node
2 24 48 java.util.regex.Pattern$Single
40 1840 (total)
java.util.regex.Pattern object externals:
ADDRESS SIZE TYPE PATH VALUE
d5e5f290 16 java.util.regex.Pattern$Node .root.next.atom.next (object)
d5e5f2a0 120 (something else) (somewhere else) (something else)
d5e5f318 16 java.util.regex.Pattern$LastNode .root.next.next.next.next.next.next.next (object)
d5e5f328 21664 (something else) (somewhere else) (something else)
d5e647c8 24 java.lang.String .pattern (object)
d5e647e0 112 [C .pattern.value [^, [, a, -, z, A, -, Z, 0, -, 9, _, ., +, -, ], +, @, [, a, -, z, A, -, Z, 0, -, 9, -, ], +, \, ., [, a, -, z, A, -, Z, 0, -, 9, -, ., ], +, $]
d5e64850 448 (something else) (somewhere else) (something else)
d5e64a10 72 java.util.regex.Pattern (object)
d5e64a58 416 (something else) (somewhere else) (something else)
d5e64bf8 16 java.util.regex.Pattern$Begin .root (object)
d5e64c08 24 java.util.regex.Pattern$BitClass .root.next.atom.val$rhs (object)
d5e64c20 272 [Z .root.next.atom.val$rhs.bits [false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, true, false, true, true, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, true, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false]
d5e64d30 24 java.util.regex.Pattern$1 .root.next.atom.val$lhs.val$lhs.val$lhs.val$lhs.val$lhs.val$lhs (object)
d5e64d48 24 java.util.regex.Pattern$1 .root.next.atom.val$lhs.val$lhs.val$lhs.val$lhs.val$lhs.val$rhs (object)
d5e64d60 24 java.util.regex.Pattern$5 .root.next.atom.val$lhs.val$lhs.val$lhs.val$lhs.val$lhs (object)
d5e64d78 24 java.util.regex.Pattern$1 .root.next.atom.val$lhs.val$lhs.val$lhs.val$lhs.val$rhs (object)
d5e64d90 24 java.util.regex.Pattern$5 .root.next.atom.val$lhs.val$lhs.val$lhs.val$lhs (object)
d5e64da8 24 java.util.regex.Pattern$5 .root.next.atom.val$lhs.val$lhs.val$lhs (object)
d5e64dc0 24 java.util.regex.Pattern$5 .root.next.atom.val$lhs.val$lhs (object)
d5e64dd8 24 java.util.regex.Pattern$5 .root.next.atom.val$lhs (object)
d5e64df0 24 java.util.regex.Pattern$5 .root.next.atom (object)
d5e64e08 32 java.util.regex.Pattern$Curly .root.next (object)
d5e64e28 24 java.util.regex.Pattern$Single .root.next.next (object)
d5e64e40 24 java.util.regex.Pattern$BitClass .root.next.next.next.atom.val$rhs (object)
d5e64e58 272 [Z .root.next.next.next.atom.val$rhs.bits [false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, true, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false]
d5e64f68 24 java.util.regex.Pattern$1 .root.next.next.next.atom.val$lhs.val$lhs.val$lhs (object)
d5e64f80 24 java.util.regex.Pattern$1 .root.next.next.next.atom.val$lhs.val$lhs.val$rhs (object)
d5e64f98 24 java.util.regex.Pattern$5 .root.next.next.next.atom.val$lhs.val$lhs (object)
d5e64fb0 24 java.util.regex.Pattern$1 .root.next.next.next.atom.val$lhs.val$rhs (object)
d5e64fc8 24 java.util.regex.Pattern$5 .root.next.next.next.atom.val$lhs (object)
d5e64fe0 24 java.util.regex.Pattern$5 .root.next.next.next.atom (object)
d5e64ff8 32 java.util.regex.Pattern$Curly .root.next.next.next (object)
d5e65018 24 java.util.regex.Pattern$Single .root.next.next.next.next (object)
d5e65030 24 java.util.regex.Pattern$BitClass .root.next.next.next.next.next.atom.val$rhs (object)
d5e65048 272 [Z .root.next.next.next.next.next.atom.val$rhs.bits [false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, true, true, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false]
d5e65158 24 java.util.regex.Pattern$1 .root.next.next.next.next.next.atom.val$lhs.val$lhs.val$lhs.val$lhs (object)
d5e65170 24 java.util.regex.Pattern$1 .root.next.next.next.next.next.atom.val$lhs.val$lhs.val$lhs.val$rhs (object)
d5e65188 24 java.util.regex.Pattern$5 .root.next.next.next.next.next.atom.val$lhs.val$lhs.val$lhs (object)
d5e651a0 24 java.util.regex.Pattern$1 .root.next.next.next.next.next.atom.val$lhs.val$lhs.val$rhs (object)
d5e651b8 24 java.util.regex.Pattern$5 .root.next.next.next.next.next.atom.val$lhs.val$lhs (object)
d5e651d0 24 java.util.regex.Pattern$5 .root.next.next.next.next.next.atom.val$lhs (object)
d5e651e8 24 java.util.regex.Pattern$5 .root.next.next.next.next.next.atom (object)
d5e65200 32 java.util.regex.Pattern$Curly .root.next.next.next.next.next (object)
d5e65220 120 (something else) (somewhere else) (something else)
d5e65298 24 java.util.regex.Pattern$Dollar .root.next.next.next.next.next.next (object)
System.out.println(ObjectSizeCalculator.getObjectSize(new gnu.trove.map.hash.TObjectIntHashMap<String>(12000, 0.6f, -1)));
System.out.println(ObjectSizeCalculator.getObjectSize(new HashMap<String, Integer>(100000)));
System.out.println(ObjectSizeCalculator.getObjectSize(3));
System.out.println(ObjectSizeCalculator.getObjectSize(new int[]{1, 2, 3, 4, 5, 6, 7 }));
System.out.println(ObjectSizeCalculator.getObjectSize(new int[100]));
164192
48
16
48
416
`JSONObject.toString().getBytes("UTF-8").length`
public class JavaSize {
private static final int NR_BITS = Integer.valueOf(System.getProperty("sun.arch.data.model"));
private static final int BYTE = 8;
private static final int WORD = NR_BITS / BYTE;
private static final int HEADER_SIZE = 8;
public static int sizeOf(Class<?> clazz) {
int result = 0;
while (clazz != null) {
Field[] fields = clazz.getDeclaredFields();
for (int i = 0; i < fields.length; i++) {
if (!Modifier.isStatic(fields[i].getModifiers())) {
if (fields[i].getType().isPrimitive()) {
Class<?> primitiveClass = fields[i].getType();
if (primitiveClass == boolean.class || primitiveClass == byte.class) {
result += 1;
} else if (primitiveClass == short.class) {
result += 2;
} else if (primitiveClass == int.class || primitiveClass == float.class) {
result += 4;
} else if (primitiveClass == double.class || primitiveClass == long.class) {
result += 8;
}
} else {
// assume compressed references.
result += 4;
}
}
}
clazz = clazz.getSuperclass();
// round up to the nearest WORD length.
if ((result % WORD) != 0) {
result += WORD - (result % WORD);
}
}
result += HEADER_SIZE;
return result;
}