understanding the Code for datacenter, host and VM's

Trying to understand how to simulate datacenter with host and VM's
According to the example problem,
A simple example showing how to create a datacenter with one host and run one cloudlet on it.

To create a datacentre:
Create host list and PE list, add the PE list to the host list and add that to the datacentre.
host has

• hostID - 0
• ram - 2048MB
• storage: 1000000 (host storage)
• bw - 10000

1.  PE list : need to store Pe id and MIPS Rating

• mips : 1000

List<Pe> peList = new ArrayList<Pe>();
int mips = 1000;
peList.add(new Pe(0, new PeProvisionerSimple(mips)));

2.  List<Host> hostList = new ArrayList<Host>();
 new Host(    hostId,
    new RamProvisionerSimple(ram),
    new BwProvisionerSimple(bw),
    storage,
    peList,
    new VmSchedulerTimeShared(peList)
   )
  );
3.  Add datacentre characteristics

• arch : x86
• os : Linux
• vmm: Xen
• time-zone: 10
• cost per sec : 3
• cost per Memory : 0.05
• cost per Storage : 0.001
• cost per bw : 0.0

DatacenterCharacteristics characteristics = new DatacenterCharacteristics(
    arch, os, vmm, hostList, time_zone, cost, costPerMem,
    costPerStorage, costPerBw);

4.  Create a datacentre
   datacenter = new Datacenter(name, characteristics, new VmAllocationPolicySimple(hostList), storageList, 0);

VmAllocationPolicySimple is an VmAllocationPolicy that chooses, as the host for a VM, the host with less PEs in use.
5.  Create VM list ( in this case 1)

• vmid : 0
• mips : 1000
• size : 10000
• ram: 512
• bw : 1000
• pesnumber : 1
• vmm: Xen

Vm vm = new Vm(vmid, brokerId, mips, pesNumber, ram, bw, size, vmm, new CloudletSchedulerTimeShared()); 
vmlist.add(vm);
broker.submitVmList(vmlist);