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publicclassDataNode{privatelongheapSize;// 用于存储堆的大小publicDataNode(){this.heapSize=getHeapSize();// 在构造方法中初始化堆大小}publiclonggetHeapSize(){returnRuntime.getRuntime().totalMemory();// 获取 JVM 总内存}publicvoiddisplayHeapSize(){System.out.println("Java Heap Size in Bytes: "...
For example, when we compare int primitive (which consumes only 4 bytes) to the Integer object which takes 16 bytes, we see that there is 300% memory overhead. 3. Estimating Object Size Using Instrumentation One way to get an estimate of an object’s size in Java is to use getObject...
String s= "";//下面三个方法参数都是 Object类型//计算指定对象及其引用树上的所有对象的综合大小,单位字节longa =RamUsageEstimator.sizeOf(s); System.out.println(a);//计算指定对象本身在堆空间的大小,单位字节longb =RamUsageEstimator.shallowSizeOf(s); System.out.println(b);//计算指定对象及其引用...
int:4 bytes; float:4 bytes; long:8 bytes; double:8 bytes。 二,引用类型: 4 bytes,即使是null值也是如此。 三,空的普通对象(无任何属性,如new Object(),不是null对象): 8 bytes。存放对象头的各种信息。 四,空的数组(即长度为0的数组,而不是null数组): ...
Object Reference word size byte 1 byte boolean 1 byte char 2 bytes short 2 bytes int 4 bytes float 4 bytes double 8 bytes long 8 bytes 对齐(Alignment)和补齐(Padding) 对齐,任何对象都是以8 bytes的粒度来对齐的。 怎么理解这句话呢?请看一个例子,new Object()产生的对象的大小是多少呢?12 byte...
publicstaticvoidmain(String[]args){Object o=newObject();} 其中new Object()是在堆上面分配,而Object o这个变量,是在main这个线程栈上面。 应用程序所有的部分都使用堆内存,然后栈内存通过一个线程运行来使用。 不论对象什么时候创建,他都会存储在堆内存中,栈内存包含它的引用。栈内存只包含原始值变量好和堆中...
Jstat是JDK自带的一个轻量级小工具。全称“JavaVirtual Machine statistics monitoring tool”,主要利用JVM内建的指令对Java应用程序的资源和性能进行实时的命令行的监控,包括了对Heap size和垃圾回收状况的监控。可见,Jstat是轻量级的、专门针对JVM的工具,非常适用。
This method is used to replace the definition of a class without reference to the existing class file bytes, as one might do when recompiling from source for fix-and-continue debugging. Where the existing class file bytes are to be transformed (for example in bytecode instrumentation) retransfor...
Size—the size of the object in bytes (if available) Last access time—the time in milliseconds that the object was last accessed Create time—the time in milliseconds when the object was created Load time—the number of milliseconds required to load the object (if the object was added...