Thread: Stacks and Priority Queues Project

So I have 3 classes in this project, and I'm to the point where I have no idea what I'm doing, so if anyone could help me with anything, I would greatly appreciate it.
When it compiles, I get a null pointer.

import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.util.Scanner;
 
 
public class Project2 {
 
	static Scanner in = new Scanner(System.in);
	static State[] stateArray;
 
 
 
	public static void main(String args[]){
 
		System.out.println("Project 2");
		System.out.println("");
		System.out.println("Stacks and Priority Queues");
		System.out.print("Enter the file name: ");
		String filename = in.next();
 
		Stack myStack = null;
		Priority sQueue = null;
		Priority wQueue = null;
		Priority mwQueue = null;
 
		try {
			BufferedReader br = new BufferedReader(new FileReader(filename));//reads in file if found
			String line = "";
			int count = -1;
			while ((line = br.readLine()) != null){  //counts how many elements will be in array to give a length
				count = count + 1;
 
				}
			myStack = new Stack(count);
			sQueue = new Priority(count);
			wQueue = new Priority(count);
			mwQueue = new Priority(count);
 
			br.close();  //closes array count
			br = new BufferedReader(new FileReader(filename)); //reads in the same file if found and adds elements to array
			br.readLine();
			count = 0;
			while ((line = br.readLine()) != null){
 
				String[] myState = line.split(",");
 
				State newState = new State(myState[0], myState[1], myState[2], Integer.parseInt(myState[3]), myState[4], Integer.parseInt(myState[5]));
 
				if(newState.getRegion().toLowerCase() == "south" || newState.getRegion().toLowerCase()=="west" || newState.getRegion().toLowerCase()=="midwest"){
					myStack.push(newState);
					}
 
			}
		br.close();  //closes array reader
 
 
		} catch (FileNotFoundException e) {
			System.out.println("");
			System.out.println("File not found.");
			System.out.println("");
 
		} catch (IOException e) {
			System.out.println("");
			System.out.println("File could not be opened.");
			System.out.println("");
		}
 
		System.out.println("");
		System.out.println("There were " + Integer.toString(myStack.size()) + " put on the stack.");
		System.out.println("");
 
		myStack.printStack();
 
		while(myStack.size()>0)
		{
			State tmp = myStack.pop();
 
			switch(tmp.getRegion().toLowerCase())
			{
			case "south":
				sQueue.insert(tmp);
				break;
			case "west":
				wQueue.insert(tmp);
				break;
			case "midwest":
				mwQueue.insert(tmp);
				break;
			}
 
		}
 
		sQueue.printQueue();
		wQueue.printQueue();
		mwQueue.printQueue();
 
		for(int i = 0; i<sQueue.Size(); i++)
		{
			State tmp = sQueue.remove();
			myStack.push(tmp);
		}
 
		for(int i = 0; i<wQueue.Size(); i++)
		{
			State tmp = wQueue.remove();
			myStack.push(tmp);
		}
 
		for(int i = 0; i<mwQueue.Size(); i++)
		{
			State tmp = mwQueue.remove();
			myStack.push(tmp);
		}
 
 
		myStack.printStack();
 
 
	}
 
}

public class Stack {
 
	static State[] stateArray;
	private int maxSize;
	private int top;
 
	public Stack(int x){
 
		maxSize = x;
		stateArray = new State[maxSize];
		top = -1;
 
	}
 
	public boolean push(State length){
 
		if(isFull())
			return false;
		else{
				stateArray[top+1] = length;
				top++;
				return true;
		}	
	}
 
	public State pop(){
 
		if(isEmpty())
			return null;
		else{
			return stateArray[top+1];
		}
 
	}
 
	public boolean isEmpty(){
 
		return (top == - 1);
 
	}
 
	public boolean isFull(){
 
		return (top+1 == maxSize);
 
	}
 
	public void printStack(){
 
		System.out.println("Stack Contents:");
		System.out.println("");
		System.out.format("%-40s%-40s%-32s%-32s%-32s%-32s\n","State Name","Capital City","State Abbr","State Population","Region","US House Seats");
		System.out.println("-------------------------------------------------------------------------------------------------------------------------------------------------------");
		for(int x = stateArray.length-1; x > -1 ; x--){
 
			stateArray[x].printName();
		}
 
	}
 
	public int size(){
 
		int count = 0;
 
		for (int i = 0; i < stateArray.length; i++){
			if (stateArray[i] != null)
				count++;
		}
		return count;
	}
 
}

public class Priority {
 
	private int maxSize;
	private State[] stateArray;
 
	public Priority(int count){
 
		maxSize = stateArray.length;
		stateArray = new State[maxSize];
 
	}
 
	public  void insert(State item){
 
		int y;
		if(Size() == 0)
			stateArray[Size()+1] = item;
		else{
			for(y = Size() - 1; y >= 0; y--){
				if( item.getStatePopulation() > stateArray[y].getStatePopulation())
					stateArray[y + 1] = stateArray[y];
				else{
					break;
				}
			}
			stateArray[y+ + 1] = item;
			Size();
		}
 
	}
 
	public State remove(){
 
		return stateArray[Size()-1];
 
	}
 
	public boolean isEmpty(){
 
		return (Size() == 0);
 
	}
 
	public boolean isFull(){
 
		return (Size() == maxSize);
 
	}
 
	public void printQueue(){
 
		System.out.println("Region Priority Queue Contents: ");
		System.out.println("");
		System.out.format("%-40s%-40s%-32s%-32s%-32s%-32s\n","State Name","Capital City","State Abbr","State Population","Region","US House Seats");
		System.out.println("-------------------------------------------------------------------------------------------------------------------------------------------------------");
		for(int x = 0; x < stateArray.length; x++){
 
			stateArray[x].printName();
 
		}
 
	}
 
	public int Size ()
	{
		int count = 0;
 
		for (int i = 0; i < stateArray.length; i++){
			if (stateArray[i] != null)
			count++;
		}
		return count;
	}
 
 
}

When it compiles, I get a null pointer.

Please copy the full text of the error message and paste it here.

BTW NullPointerExceptions happen when a program is executed, not when it is compiled.

Exception in thread "main" java.lang.NullPointerException
at Priority.<init>(Priority.java:9)

There is a variable with a null value on line 9. Look at line 9 in the your source and see what variable is null. Then backtrack in the code to see why that variable does not have a valid value.
If you can not tell which variable it is, add a println just before line 9 and print out the values of all the variables on that line.

What variable has the null value? Where should that variable have been assigned a value?

Exception in thread "main" java.lang.NullPointerException
at Stack.printStack(Stack.java:57)

Same as before. Look at line 57, find the variable and find why it does not have a valid value.