Building a String array from a text file without collection classes - arrays

Question

I am trying to build an array from a buffered in text file. This class is used by another class with a main method. What I have only prints the file... what I need is to have an array of strings, built line by line, mirroring the text file. I need to be able to then search against that array using a String from user input (that part will be in main method too) that will name a product, and find the corresponding price. I can't use things like ArrayList, Maps, Vectors, etc. This is in Java8.
/**
* A class that reads in inventory from vmMix1 text file using BufferedReader
* # author Michelle Merritt
*/
import java.io.*;
public class VendingMachine1
{
BufferedReader inInvFile1 = new BufferedReader(
new FileReader("vmMix1.txt"))
/**
* A method to print vending machine 1 inventory
*/
public void printVM1()
{
try
{
String vm1Line;
while((vm1Line = inInvFile1.readLine()) != null)
{
// This is what I was using for now to simply print my file
System.out.println(vm1Line);
}
}
catch(IOException e)
{
System.out.println("I/O Error: " + e);
}
}
}
This is the code that created my text file, since I can't seem to see how I attach the text file instead.
/**
* A class that creates the inventory found in vending machine #1, using
* a PrintWriter stream.
* # author Michelle Merritt
*/
import java.io.*;
public class VMMix1
{
public static void main(String[] args)
{
String [] product = {"Coke", "Dr. Pepper", "Sprite", "RedBull",
"Cool Ranch Doritos", "Lay's Potato Chips",
"Pretzels", "Almonds", "Snickers", "Gummi Bears",
"Milky Way", "KitKat"};
String [] packaging = {"bottle", "can", "can", "can", "bag", "bag",
"bag", "bag", "wrapper", "bag", "wrapper",
"wrapper"};
float [] price = {2.25f, 1.75f, 1.75f, 2.00f, 1.00f, 1.00f, 0.75f, 1.50f,
1.25f, 1.00f, 1.25f, 1.25f};
int [] quantity = {10, 10, 10, 12, 8, 10, 12, 9, 7, 11, 10, 8};
try(PrintWriter outFile = new PrintWriter("vmMix1.txt"))
{
for (int index = 0; index < product.length; index++)
{
outFile.printf("%-18s %-10s: $%.2f qty: %3d\n", product[index],
packaging[index], price[index], quantity[index]);
}
}
catch (IOException except)
{
System.out.println("IOException: " + except.getMessage());
}
}
}
I need for this thing to be dynamic. As the program runs, and something is purchased, I will have to account for losing inventory and changing the amount of money in the vending machine (there's another class for currency that houses quantities of denominations of money). I have to maintain the values in the array and reprint the updated array. Any help is much appreciated.

Answer 1

You may use Java8 stream API
String[] array = reader.lines().toArray(String[]::new);
You could even skip the buffer creation using
try (Stream<String> stream = Files.lines(Paths.get("vmMix1.txt"))) {
String [] array = stream.toArray(String[]::new);
}
Pre-Java8, probably one of the shortest way is to read the entire file into a string, and split it (ways to read a reader into string can be found here):
String[] array = fileAsString.split('\\n');
Of course you could also built the array in your loop and increase it for every line using System.arraycopy (which can be quite slow in that case).
String[] array = new String[0];
while((vm1Line = inInvFile1.readLine()) != null) {
String[] newArray = new String[array.length + 1];
System.arraycopy(array, 0, newArray, 0, array.length);
newArray[array.length] = vm1Line;
array = newArray;
}
You may optimize this approach by creating a larger array first, fill in the lines, increase size of the array as needed (using arraycopy), and finally shrink the array to the number of written lines.
Thats more or less what an array list does. So in case you may use the collections api, you could simply do
List<String> list = new ArrayList<>();
while((vm1Line = inInvFile1.readLine()) != null) {
list.add(vm1Line);
}
String[] array = list.toArray(new String[list.size()]);

Answer 2

Hope it helps.
Stream<String> lines = Files.lines(Paths.get("C:/SelfStudy/Input.txt"));
String[] array = lines.toArray(String[]::new);