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| package com.super2bai.jvm;
import java.lang.reflect.Field;
import java.util.Collection;
import org.omg.PortableServer.ServantActivator;
import com.javamex.classmexer.MemoryUtil;
import com.javamex.classmexer.MemoryUtil.VisibilityFilter;
import sun.misc.Unsafe;
public class TheObjectMemory {
private static Unsafe UNSAFE;
static {
try {
Field theUnsafe = Unsafe.class.getDeclaredField("theUnsafe");
theUnsafe.setAccessible(true);
UNSAFE = (Unsafe) theUnsafe.get(Unsafe.class);
} catch (Exception e) {
e.printStackTrace();
}
}
public static void main(String[] args) throws NoSuchFieldException {
testObjectLayout();
testMemoryUsage();
testPaddingLocation();
testCompactFields();
testReferenceAllocate();
testDeepMemoryUsage();
testObjectArrayMemoryUsage();
}
private static class ObjectA {
String str;
int i1;
byte b1;
byte b2;
int i2;
Object obj;
byte b3;
}
public static void testObjectLayout() {
System.out.println("****测试对象内存布局****");
int objectRefSize = UNSAFE.arrayIndexScale(ObjectA[].class);
System.out.println("ObjectA, Oop指针, length=" + objectRefSize);
Field[] fields = ObjectA.class.getDeclaredFields();
for (Field f : fields) {
System.out.println("ObjectA, " + f.getType() + " " + f.getName() + " offset: " + UNSAFE.objectFieldOffset(f));
}
}
public static void testMemoryUsage() {
System.out.println("****测试对象内存占用****");
ObjectA a = new ObjectA();
System.out.println("ObjectA.class, memoryUsage : " + MemoryUtil.memoryUsageOf(a));
long noBytes1 = MemoryUtil.deepMemoryUsageOf(a, VisibilityFilter.ALL);
System.out.println("ObjectA.class, VisibilityFilter=All, deepMemoryUsageOf=" + noBytes1);
}
private static class ObjectB {
long a;
long b;
}
public static void testPaddingLocation() throws NoSuchFieldException {
System.out.println("****测试对齐填充位置****");
ObjectB b = new ObjectB();
System.out.println("ObjectB, memoryUsage : " + MemoryUtil.memoryUsageOf(b));
System.out.println("ObjectB, long a offset : " + UNSAFE.objectFieldOffset(ObjectB.class.getDeclaredField("a")));
System.out.println("ObjectB, long b offset : " + UNSAFE.objectFieldOffset(ObjectB.class.getDeclaredField("b")));
}
private static class ObjectC {
long a;
int b;
}
public static void testCompactFields() throws NoSuchFieldException, SecurityException {
System.out.println("****测试空隙插入****");
ObjectC obj = new ObjectC();
System.out.println("ObjectC, memoryUsage : " + MemoryUtil.memoryUsageOf(obj));
System.out.println("ObjectC, long a offset : " + UNSAFE.objectFieldOffset(ObjectC.class.getDeclaredField("a")));
System.out.println("ObjectC, int b offset : " + UNSAFE.objectFieldOffset(ObjectC.class.getDeclaredField("b")));
}
private static class ObjectD {
int a;
long b;
String str;
}
public static void testReferenceAllocate() throws NoSuchFieldException, SecurityException {
System.out.println("****测试基本类型分配后再分配引用类型****");
ObjectD obj = new ObjectD();
System.out.println("ObjectD, memoryUsage : " + MemoryUtil.memoryUsageOf(obj));
System.out.println("ObjectD, int a offset : " + UNSAFE.objectFieldOffset(ObjectD.class.getDeclaredField("a")));
System.out.println("ObjectD, long b offset : " + UNSAFE.objectFieldOffset(ObjectD.class.getDeclaredField("b")));
System.out.println("ObjectD, String str offset : " + UNSAFE.objectFieldOffset(ObjectD.class.getDeclaredField("str")));
}
static class TheInnerObject {
int innerA;
}
TheInnerObject innerObject = new TheInnerObject();
public static void testDeepMemoryUsage() {
System.out.println("****测试对象总大小，包含引用对象占用的内存****");
TheObjectMemory obj = new TheObjectMemory();
System.out.println("TheObjectMemory memoryUsage : " + MemoryUtil.memoryUsageOf(obj));
TheInnerObject innerObj = new TheInnerObject();
System.out.println("TheInnerObject memoryUsage : " + MemoryUtil.memoryUsageOf(innerObj));
System.out.println("TheObjectMemory deepMemoryUsageOf : " + MemoryUtil.deepMemoryUsageOf(obj));
}
int a;
String str = "hello";
public static void testObjectArrayMemoryUsage() {
System.out.println("****测试数组对象占用内存大小***");
TheObjectMemory[] objArray = new TheObjectMemory[1];
TheObjectMemory obj = new TheObjectMemory();
objArray[0] = obj;
System.out.println("objArray memoryUsage : " + MemoryUtil.memoryUsageOf(objArray));
System.out.println("objArray deepMemoryUsageOf : " + MemoryUtil.deepMemoryUsageOf(objArray));
System.out.println("obj memoryUsage : " + MemoryUtil.memoryUsageOf(obj));
System.out.println("obj deepMemoryUsageOf : " + MemoryUtil.deepMemoryUsageOf(obj));
System.out.println("first item offset : " + UNSAFE.arrayBaseOffset(objArray.getClass()));
}
}
|
