e055. getting the size of the heap.txt

这里面包含了一百多个JAVA源文件

The heap is the area in memory in which objects are created. 
    // 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();