Exception in thread "pool-1-thread-7" java.lang.NullPointerException - thread-exceptions

Question

I'm trying to figure it out y i get this exception as i wrote in the title.
i'm building a multi thread MMU (memory management unit) project, first i initialize and add some pages into the ram and to my HD also and then i create processes and running all the system. a bit of information about the project:
into runConfig i;m reading a json file with a list of processCycles and every processCycles including a list of processCycle that including a list of pageIds with a list of data of those pages.
i think i did everything ok but still i get this exception, can somebody help me?
MMUDriver is the class that run all the systems:
package hit.driver;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.lang.reflect.InvocationTargetException;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.concurrent.Executor;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import com.google.gson.Gson;
import com.google.gson.JsonIOException;
import com.google.gson.JsonSyntaxException;
import com.google.gson.stream.JsonReader;
import com.hit.algorithm.IAlgoCache;
import com.hit.algorithm.LRUAlgoCacheImpl;
import com.hit.algorithm.MRUAlgoCacheImpl;
import com.hit.algorithm.RandomReplacementAlgoCacheImpl;
import hit.memoryunits.HardDisk;
import hit.memoryunits.MemoryManagementUnit;
import hit.memoryunits.MemoryManagementUnitTest;
import hit.memoryunits.Page;
import hit.processes.ProcessCycles;
import hit.processes.Process;
import hit.processes.RunConfiguration;
#SuppressWarnings("unused")
public class MMUDriver {
private static final String CONFIG_FILE_NAME="Configuration.json";
// private static final String CONFIG_FILE_NAME="test.json";
//read from JSON file the lists of processCycles
private static RunConfiguration readConfigurationFile() throws JsonIOException, JsonSyntaxException, FileNotFoundException{
RunConfiguration runConfig = new Gson().fromJson(new JsonReader(new FileReader(CONFIG_FILE_NAME)), RunConfiguration.class);
return runConfig;
}
//
private static List<Process> createProcesses(List<ProcessCycles> processCycles,MemoryManagementUnit mmu ){
int i=0;
List<Process> processList = new ArrayList<Process>();
for ( ProcessCycles currentListProcess : processCycles) {
Process process = new Process(++i , mmu , currentListProcess);
processList.add(process);
}
return processList;
}
//
private static void runProcesses(List<Process> processes){
//Executor is a interface that take care of threads מתי מתחיל טרד מתי נגמר איך הם ירוצו במקביל וכו'
//thread pool - אוסף של threads
ExecutorService executorservice = Executors.newCachedThreadPool();
for (Process process : processes)
executorservice.execute(process);
executorservice.shutdown();//
}
//
public static void main(String[] args) throws java.lang.InterruptedException,
InvocationTargetException, JsonIOException, JsonSyntaxException, ClassNotFoundException, IOException{
CLI cli = new CLI(System.in,System.out);
String [] configuration;
while((configuration = cli.getConfiguration()) != null){
IAlgoCache<Long, Long> algo = null;
int capacity = Integer.valueOf(configuration[1]);
switch(configuration[0]){ //which configuration to play on LRU|MRU|RR
case "LRU":
algo = new LRUAlgoCacheImpl<Long, Long>(capacity);
break;
case "MRU":
algo = new MRUAlgoCacheImpl<Long, Long>(capacity);
break;
case "RR":
algo = new RandomReplacementAlgoCacheImpl<Long, Long>(capacity);
break;
}
MemoryManagementUnit mmu = new MemoryManagementUnit(algo, capacity);
MemoryManagementUnitTest.test(mmu);//add some pages to ram for test
RunConfiguration runConfig = readConfigurationFile(); //Getting the user request pages throw json file
List<ProcessCycles> processCycles = runConfig.getProcessesCycles();
List<Process> processes = createProcesses(processCycles , mmu);
runProcesses(processes);
Map<Long, Page<byte[]>> bla= mmu.getRam().getRamPages();
System.out.println("1");
// mmu.shoutDown();
}
}
}
Process is like a thread in this project
package hit.processes;
import java.io.IOException;
import java.util.List;
import hit.memoryunits.MemoryManagementUnit;
import hit.memoryunits.Page;
#SuppressWarnings("unused")
public class Process implements Runnable {
private int id;
private MemoryManagementUnit mmu;
private ProcessCycles processCycles;
private Thread processThread=null;
public Process(int id, MemoryManagementUnit mmu, ProcessCycles processCycles){
this.id=id;
this.mmu=mmu;
this.processCycles=processCycles;
}
public int getId(){
return id;
}
public void setId(int id){
this.id=id;
}
/*
public void start(){
if(processThread==null)
processThread = new Thread(this,"process"); //
processThread.start();
}*/
#Override
public void run() {
synchronized(mmu){
//runing on all the list of processCycles
for (ProcessCycle currentProcessCycle : processCycles.getProcessCycles()) {
List<Long> pages = currentProcessCycle.getPages();
List<byte[]> data = currentProcessCycle.getData();
Page<byte[]>[] pagesList = null;
//creating a boolean array to know if the page is for writing or reading in size of pages.size()
boolean [] writePages = new boolean[pages.size()];
for (int i = 0; i < pages.size(); i++)
if(data.get(i) == null) //if the page is empty
writePages[i] = false;
else{
writePages[i] = true ;//if there is data in the page and we want to write it to the ram
}
try {
// Getting the pages from ram to see which we shall update
pagesList = mmu.getPages(pages.toArray(new Long[pages.size()]), writePages);
}
catch (ClassNotFoundException e1) {
e1.printStackTrace();
} catch (IOException e1) {
e1.printStackTrace();
}
for (int j = 0; j < pages.size(); j++)
if(writePages[j] == true) //if the page isn't for read only
pagesList[j].setContent(data.get(j));
try {
Thread.sleep(currentProcessCycle.getSleepMs());
}
catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}
}
MMU class is that class that take care of all the requests from the user and manage all the pagging
package hit.memoryunits;
import java.io.FileNotFoundException;
import java.io.IOException;
import com.hit.algorithm.IAlgoCache;
public class MemoryManagementUnit {
private IAlgoCache<Long,Long> algo;
private RAM<Long, Page<byte[]>> ram;
public MemoryManagementUnit(IAlgoCache<Long, Long> algo, int ramCapacity) {
this.algo = algo;
this.ram= new RAM<Long, Page<byte[]>>(ramCapacity);
}
#SuppressWarnings("null")
public Page<byte[]> [] getPages(Long [] pageIds , boolean [] writePages) throws IOException, ClassNotFoundException{
for (int i = 0; i < pageIds.length; i++) {
if(algo.getElement((long) pageIds[i].hashCode())== null)//the page isn't exist in the cache
if(!ram.isFull())
{
if(writePages[i] == true){//if the page is for write we need to overwrite data
Page<byte[]> pageToRam = null;
pageToRam.setPageId(pageIds[i]);
pageToRam.setContent(null);
ram.addPage(pageToRam);// ram is not full need to upload from hd
}
else{//if the page is for read-only so we need to upload the page from HD
ram.addPage(HardDisk.getInstance().pageFault(pageIds[i]));// ram is not full need to upload from hd
}
algo.putElement(Long.valueOf(pageIds[i].hashCode()),pageIds[i]);//update cache
}
else
{
Page<byte[]> pageToRemove = ram.getPage(algo.putElement(Long.valueOf(pageIds[i].hashCode()),pageIds[i]));
ram.removePage(pageToRemove);
ram.addPage(HardDisk.getInstance().pageReplacement(pageToRemove,pageIds[i]));// ram full need to do replacement
algo.putElement(Long.valueOf(pageIds[i].hashCode()),pageIds[i]);//update cache
}
}
return ram.getPages(pageIds);
}
public RAM<Long, Page<byte[]>> getRam(){
return ram;
}
public IAlgoCache<Long,Long> getAlgo(){
return algo;
}
public void setAlgo(IAlgoCache<Long,Long> algo){
this.algo = algo;
}
public void setRam(RAM<Long, Page<byte[]>> ram){
this.ram = ram;
}
public void shoutDown() throws FileNotFoundException, IOException, ClassNotFoundException{
HardDisk.getInstance().saveToDisk(this.getRam().getRamPages());
}
}