Question

I recently jumped back into programming and decided to learn Java as my first major language. I got pretty far without any major issues, until I started delving into file saving. I pretty much went with the first method I came across; input and output streaming. The problem I’m encountering is in the method “analyzeIncidents.” If no user data exists then the method runs properly and I get the expected output. If user data DOES exist, then the first if…then statement in “analyzeIncidents” will run, but it will never find the conditional statement to be true. Once I delete the UserData.sav file, however, everything works again. I’ve spent hours checking the output at all stages of the program, but so far can find no reason why the if…then statement fails when using loaded data but succeeds otherwise. I’ve also tried saving then loading the data right before it gets tossed to “analyzeIncidents” and it works on the first run through, but fails on any attempt afterwards. Hopefully you guys can point out what I’m sure is an obvious mistake on my part.

MAIN:

import java.io.*;
import java.util.*;


public class nutralyzeApp {


    static Scanner userInput = new Scanner(System.in);

    public static void main(String[] args) {

        int elements = 0;
        int selectedElement = 0;
        int[][] incidentAnalysis = new int[2][50];
        String newElement = "999";
        String[][] data2012 = new String[366][51];


        //Checks to see if previous save file exists. If not, creates new save file.
        File f = new File("C:/Users/Liam/Dropbox/Workspace/Nutralyze/UserData.sav");
        if(f.exists()) {
            System.out.println("Previous work session loaded.");
            data2012 = loadData();
        } else {
            data2012[0][0] = "granola";
            data2012[0][1] = "gluten";
            data2012[0][2] = "sugar";
            data2012[0][3] = "beef";
            data2012[1][0] = "dairy";
            data2012[8][0] = "cheese";
            data2012[59][0] = "pizza";
            data2012[59][1] = "chips";
            data2012[206][0] = "beer";
            data2012[206][1] = "cheese";

            data2012[8][50] = "incident";
            data2012[59][50] = "incident";
            data2012[85][50] = "incident";
            data2012[190][50] = "incident";
            data2012[206][50] = "incident";

            saveData(data2012);
        }

        System.out.println("What day is it? ");
        int currentDay = userInput.nextInt();
        elements = numberOfElements(currentDay,data2012);

        System.out.println("Elements consumed that day: " + elements);

        System.out.println("What element would you like to add?");
        newElement = userInput.next();

        while (!newElement.equals("49")) {
            data2012 = addElement(currentDay,elements,newElement,data2012);
            elements = numberOfElements(currentDay,data2012);
            System.out.println("What element would you like to add?");
            newElement = userInput.next();
        }

        System.out.print("Which element would you like to see? ");
        selectedElement = userInput.nextInt();

        while (selectedElement != 49) {
            System.out.println("The element you selected is: " + data2012[currentDay][selectedElement]);
            System.out.println("You typed: " + selectedElement);
            System.out.print("Which element would you like to see? ");
            selectedElement = userInput.nextInt();
        }

        data2012 = gatherElements(data2012);
        incidentAnalysis = analyzeIncidents(data2012);  

        for (int x=0;x<10;x++) {
            System.out.print(data2012[365][x] + " --> " + incidentAnalysis[0][x] + "/" + incidentAnalysis[1][x]+ "\n");
        }

        //Resets data and saves to file.
        for (int x=0;x<50;x++) {
            data2012[365][x] = null;
        }   

        saveData(data2012); 
    }

METHODS:

    private static int[][] analyzeIncidents(String[][] userData) {

        boolean found = false;
        int elements1 = 0;
        int elements2 = 0;
        int incidentCounter = 0;
        int currentIncident = 0;
        int[] incidentDates = new int[365];
        int[][] incidentReport = new int[2][50];

        for (int x=0;x<365;x++) {
            if (userData[x][50]=="incident") {
                incidentDates[incidentCounter]=x;
                incidentCounter++;
                System.out.println(userData[x][50]);
            } 
        }
System.out.println(incidentCounter + "          " + userData[8][50]);
        elements1 = numberOfElements(365,userData);
        for (int x=0;x<elements1;x++) {

            for (int y=0;y<incidentCounter;y++) {

                currentIncident = incidentDates[y];
                elements2 = numberOfElements(currentIncident,userData);

                for (int z=0;z<elements2;z++) {
                    if ((userData[365][x]==userData[currentIncident][z]) && (found==false)) {
                        incidentReport[0][x]++;
                        incidentReport[1][x]++;
                    } else if ((userData[365][x]==userData[currentIncident][z]) && (found==true)) {
                        incidentReport[1][x]++;
                    }
                }


            }
        }

        return incidentReport;
    }

    private static String[][] gatherElements(String[][] userData) {

        int z = 0;
        int elements = 0;
        int uniqueElements = 0;
        boolean found = false;

        for (int x=0;x<50;x++) {
            userData[365][x] = null;
        }
        //userData[365][0] = userData[0][0];

        for (int x=0;x<365;x++) {
            elements = numberOfElements(x,userData);

            for (int y=0;y<elements;y++) {
                while (z<50) {
                    if (userData[365][z]!=userData[x][y]) {
                        z++;
                        found=false;
                    } else if (userData[365][z]==userData[x][y]) {
                        z=50;
                        found=true;
                        break;
                    }
                }
                z=0;

                if (found==false) {
                    userData[365][uniqueElements] = userData[x][y];
                    uniqueElements++;
                }
            }
        }
        return userData;
    }

    private static String[][] addElement(int day,int position,String newElement,String[][] userData) {

        userData[day][position] = newElement;
        return userData;
    }

    private static int numberOfElements(int day, String[][] userData) {

        int x = 0;

        while (userData[day][x] != null && x < 365) {
            x++;
        }
        return x;
    }

    private static void saveData(String[][] data2012) {

        try{
            // Open a file to write to, named UserData.sav
            FileOutputStream saveFile = new FileOutputStream("UserData.sav");
            // Create an ObjectOutputStream to put objects into save file
            ObjectOutputStream save = new ObjectOutputStream(saveFile);
            // Now we do the save
            save.writeObject(data2012);
            // Close the file
            save.close(); // This also closes saveFile  
        }
        catch(Exception exc){
        exc.printStackTrace(); // If there was an error, print the info
        }
    }

    private static String[][] loadData() {

        String[][] userData = new String[366][51];

        try{
           // Open file to read from, named UserData.sav
           FileInputStream saveFile = new FileInputStream("UserData.sav");

           // Create an ObjectInputStream to get objects from save file
           ObjectInputStream save = new ObjectInputStream(saveFile);

           // Now we do the restore
           // readObject() returns a generic Object, we cast those back
           // into their original class type
           // For primitive types, use the corresponding reference class

           userData = (String[][]) save.readObject();

           // Close the file
           save.close(); // This also closes saveFile
        }
        catch(Exception exc){
        exc.printStackTrace(); // If there was an error, print the info
        }
              return userData;
    }

}

Answer 1

You’re comparing strings by their references, instead of for semantic equality. This:

if (userData[x][50]=="incident")

should be:

if (userData[x][50].equals("incident"))

Or if you want to continue even if userData[x][50] is null:

if ("incident".equals(userData[x][50]))

You do the same elsewhere, too:

if (userData[365][z]!=userData[x][y]) {
...
} else if (userData[365][z]==userData[x][y]) {
}

This should be:

if (!userData[365][z].equals(userData[x][y])) {
...
} else {
}

(You don’t need the second condition, as it’s the exact opposite of the first.)