The com.sun.management.OperatingSystemMXBean.getTotalPhysicalMemorySize()  method description says the following: 
    /**
     * Returns the total amount of physical memory in bytes.
     *
     * @deprecated Use {@link #getMemorySize()} instead of
     * this historically named method.
     *
     * @implSpec This implementation must return the same value
     * as {@link #getMemorySize()}.
     *
     * @return the total amount of physical memory in  bytes.
     **/

However, there is no such method getMemorySize(). The proper method name is getTotalMemorySize(). The method description needs to be changed to correct this.