null pointer

[Dustin Schreader]

Hello I've been fighting with this code for the past few hours and I don't know why i'm getting a null pointer. For some reason my createArray method is making arrays that all contain null.
Here is the infile ServiceMaster.csv

89,calahan,jo2b,fr1c,fr2c,pt
90,white,jo2b,fr1c,fr2c,pt
91,hemmer,jo2b,fr1c,fr2c,pt
92,johnson,jo2b,fr1c,fr2c,pt
93,lane,jo2b,fr1c,fr2c,pt

And here is my code

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

class ServiceMaster implements SMInterface {

    private int rowSize = 6;
    private String[] dataArray;
    private String[][] rows = new String[rowSize][5];
    private String ptName = " ", ptCode = " ", dr = " ", floor = " ", time = " ";
    private String drCode = " ", drName = " ", gen = " ", icu = " ", pcu = " ", type = " ";

    public ServiceMaster() {
    }

    //creates array for use in other methods
    public String[][] createArray() {

        try {
            BufferedReader serviceMasterCSV =
                    new BufferedReader(new FileReader("ServiceMaster.csv"));

            String dataRow = serviceMasterCSV.readLine();
            int x = 0;


            while (dataRow != null) {


                dataArray = dataRow.split(",");
                //System.arraycopy(dataArray, 0, rows[x], 0, dataArray.length);

                for (int r = 0; r < dataArray.length; r++) {

                    rows[x][r] = dataArray[r];
                }
                x++;

                dataRow = serviceMasterCSV.readLine(); // Read next line of data.
System.out.println(Arrays.deepToString(rows));
            }
            serviceMasterCSV.close();

        } catch (IOException e) {
        }

        return rows; //returns array

    }

    public void addPt(String ptCode, String ptName, String dr, String floor, String time) {
        rows = createArray();

        BufferedReader in = new BufferedReader(new InputStreamReader(System.in));

        for (int w = 0; w < rowSize; w++) {

            if (rows[w][0].equals("000")) {
                rows[w][0] = ptCode;
                rows[w][1] = ptName;
                rows[w][2] = dr;
                rows[w][3] = floor;
                rows[w][4] = time;
                rows[w][5] = "pt";
                System.out.println("Patient " + rows[w][0] + " added.");
                w = rowSize;
            } else if (rowSize == (w + 1)) {
                //add extra row to array
                rowSize++;
                rows[w][0] = ptName;
                rows[w][1] = ptCode;
                rows[w][2] = dr;
                rows[w][3] = floor;
                rows[w][4] = time;
                rows[w][5] = "pt";
                System.out.println("pt " + rows[w][0] + " added.");
                w = rowSize;

            }
        }

        try {
            BufferedWriter writer = new BufferedWriter(new FileWriter("ServiceMaster.CSV"));

            for (int n = 0; n < rowSize; n++) {
                writer.write(rows[n][0]);
                writer.write(",");
                writer.write(rows[n][1]);
                writer.write(",");
                writer.write(rows[n][2]);
                writer.write(",");
                writer.write(rows[n][3]);
                writer.write(",");
                writer.write(rows[n][4]);
                writer.write(",");
                writer.write(rows[n][5]);
                writer.write("\n");
            }
            writer.close();

        } catch (IOException e) {
        }
    }

    public void addDr(String drCode, String drName, String gen, String icu, String pcu) {

        rows = createArray();

        BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
        //rows = createArray();

        for (int w = 0; w < rowSize; w++) {
            if (rows[w][0].equals(drCode) && rows[w][3].equals(gen)) {
                System.out.println("The doctor has already been added to the service list");
            } else if (rows[w][0].equals("000")) {
                rows[w][0] = drCode;
                rows[w][1] = drName;
                rows[w][2] = gen;
                rows[w][3] = icu;
                rows[w][4] = pcu;
                rows[w][5] = "dr";
                System.out.println("Doctor " + rows[w][1] + " added.");
                w = rowSize;
            } else if (rowSize == (w + 1)) {
                //add extra row to array
                rowSize++;
                rows[w][0] = drCode;
                rows[w][1] = drName;
                rows[w][2] = gen;
                rows[w][3] = icu;
                rows[w][4] = pcu;
                rows[w][5] = "dr";
                System.out.println("Doctor " + rows[w][1] + " added.");
                w = rowSize;

            }
        }

        try {
            BufferedWriter writer = new BufferedWriter(new FileWriter("ServiceMaster.CSV"));

            for (int n = 0; n < rowSize; n++) {
                writer.write(rows[n][0]);
                writer.write(",");
                writer.write(rows[n][1]);
                writer.write(",");
                writer.write(rows[n][2]);
                writer.write(",");
                writer.write(rows[n][3]);
                writer.write(",");
                writer.write(rows[n][4]);
                writer.write(",");
                writer.write(rows[n][5]);
                writer.write("\n");
            }
            writer.close();

        } catch (IOException e) {
        }

    }

    public boolean search(String code, String name) {
        rows = createArray();
        boolean stat = false;
        String output = "";
        //System.out.println(Arrays.deepToString(rows));

        for (int w = 0; w < rowSize; w++) {
            if (rows[w][0].equals(code) || rows[w][1].equals(name)) {
                System.out.println("Found");

                if (rows[w][5].equals("pt")) {
                    ptCode = rows[w][0];
                    ptName = rows[w][1];
                    dr = rows[w][2];
                    floor = rows[w][2];
                } else {
                    drCode = rows[w][0];
                    drName = rows[w][1];
                    gen = rows[w][2];
                    icu = rows[w][3];
                    pcu = rows[w][4];
                }

                stat = true;
                w = rowSize;
            } else if (rowSize == w) {
                System.out.println("not found");
                stat = false;
            }
        }
        return stat;
    }

    public void addRoom(String ptCode, String floor) {
        if (search(ptCode, " ")) {
            addPt(ptName, ptCode, dr, floor, getDate());
        }
    }

    public void addMedications(String ptCode, String name, String dose) {
    }

    public String displayInfo() {

        String info = ptName + " " + ptCode + " " + dr + " " + floor + " " + getDate();

        return info;
    }

    //finds when pt info was last accesed
    public String getDate() {
        DateFormat dateFormat = new SimpleDateFormat("yyyy/MM/dd HH:mm:ss");
        Date date = new Date();
        return dateFormat.format(date);
    }
}

[Jesper de Jong]

Do you get a NullPointerException with a stack trace printed?

Carefully look at the stack trace. It will tell you exactly in which line of your code the NullPointerException happens and what chain of method calls happened to get there. Look through your code at the line where the exception happens and where the call came from. Then try to discover what is null when it shouldn't be, and try to reason what exactly happened (the stack trace will tell you exactly what the chain of method calls was - use that information).

I haven't looked at your code in detail, but one common mistake made with arrays is forgetting that creating an array fills the whole array with nulls; it does not fill the array with new objects:

// Creates a new array with ten nulls - not ten MyClass objects!
MyClass[] data = new MyClass[10];

// If you want to have the array with ten new MyClass objects, then you have to initialize the elements yourself
for (int i = 0; i < data.length; ++i) {
    data[i] = new MyClass();
}

[Rob Spoor]

Can you please post the exception stack trace? It tells us (and you as well) where the exception occurred.

[Dustin Schreader]

Is this it?

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
        at ServiceMaster.search(ServiceMaster.java:171)
        at ServiceMasterForm.searchButtonActionPerformed(ServiceMasterForm.java:263)
        at ServiceMasterForm.access$000(ServiceMasterForm.java:16)
        at ServiceMasterForm$1.actionPerformed(ServiceMasterForm.java:83)
        at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2028)
        at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2351)
        at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:387)
        at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:242)
        at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:236)
        at java.awt.AWTEventMulticaster.mouseReleased(AWTEventMulticaster.java:272)
        at java.awt.Component.processMouseEvent(Component.java:6373)
        at javax.swing.JComponent.processMouseEvent(JComponent.java:3267)
        at java.awt.Component.processEvent(Component.java:6138)
        at java.awt.Container.processEvent(Container.java:2085)
        at java.awt.Component.dispatchEventImpl(Component.java:4735)
        at java.awt.Container.dispatchEventImpl(Container.java:2143)
        at java.awt.Component.dispatchEvent(Component.java:4565)
        at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4621)
        at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4282)
        at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4212)
        at java.awt.Container.dispatchEventImpl(Container.java:2129)
        at java.awt.Window.dispatchEventImpl(Window.java:2478)
        at java.awt.Component.dispatchEvent(Component.java:4565)
        at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:679)
        at java.awt.EventQueue.access$000(EventQueue.java:85)
        at java.awt.EventQueue$1.run(EventQueue.java:638)
        at java.awt.EventQueue$1.run(EventQueue.java:636)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:87)
        at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:98)
        at java.awt.EventQueue$2.run(EventQueue.java:652)
        at java.awt.EventQueue$2.run(EventQueue.java:650)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:87)
        at java.awt.EventQueue.dispatchEvent(EventQueue.java:649)
        at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:296)
        at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:211)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:201)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:196)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:188)
        at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)

[Jesper de Jong]

Yes. Note that the second line tells you that the exception happened in line 171 of ServiceMaster.java, which was called from line 263 of ServiceMasterForm.java, which was called from line 16 of ServiceMasterForm.java etc.

Looking at the code you posted, the line numbers probably don't correspond exactly with what you have in your source file exactly, because line 171 only contains a System.out.println statement that can't normally cause a NullPointerException. It's probably line 170:

if (rows[w][0].equals(code) || rows[w][1].equals(name)) {

Most likely rows[w][0] or rows[w][1] is null. When you try to call a method on a null, as you are trying to call the equals method, then you'll get a NullPointerException.

Make sure that the array actually contains objects, or check for null before calling the equals method on whatever is in the array.

[Dustin Schreader]

Yes, I figured that the problem was coming from

if (rows[w][0].equals(code) || rows[w][1].equals(name)) { 

so that must mean that the array i'm creating is null but I looked through the createArray method and I don't see how it could be null.

[Jesper de Jong]

Either:

rows is null

rows[w] is null

rows[w][0] and/or rows[w][1] is null

You could add some System.out.println statements before line 170 to check:

System.out.println("rows = " + rows);
System.out.println("rows[w] = " + rows[w]);
System.out.println("rows[w][0] = " + rows[w][0]);
System.out.println("rows[w][1] = " + rows[w][1]);

[Dustin Schreader]

I added

System.out.println(Arrays.deepToString(rows));

on line 167 and I got

[
    [null, null, null, null, null],
    [null, null, null, null, null],
    [null, null, null, null, null],
    [null, null, null, null, null],
    [null, null, null, null, null],
    [null, null, null, null, null]
]
// line breaks added for readability - Rob Spoor

There must be something wrong with my createArray method correct? or am I not calling the method correctly?

[James Boswell]

Hi

Is there a problem when the CSV file is read? I couldn't help but notice that you are 'swallowing' any IOException in the createArray method. This is generally bad practice. At a minimum, add the following to your catch block:

e.printStackTrace();

[Dustin Schreader]

I usually have something there but netbeans was flagging it for some reason so I just deleted it for now. The stack trace looks different now. Why would there be a problem at line 120, I'm not even calling that method?

java.io.FileNotFoundException: ServiceMaster.csv (No such file or directory)
        at java.io.FileInputStream.open(Native Method)
        at java.io.FileInputStream.<init>(FileInputStream.java:120)
        at java.io.FileInputStream.<init>(FileInputStream.java:79)
        at java.io.FileReader.<init>(FileReader.java:41)
        at ServiceMaster.createArray(ServiceMaster.java:21)
        at ServiceMaster.search(ServiceMaster.java:166)
        at ServiceMasterForm.searchButtonActionPerformed(ServiceMasterForm.java:262)
        at ServiceMasterForm.access$000(ServiceMasterForm.java:16)
        at ServiceMasterForm$1.actionPerformed(ServiceMasterForm.java:83)
        at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2028)
        at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2351)
        at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:387)
        at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:242)
        at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:236)
        at java.awt.AWTEventMulticaster.mouseReleased(AWTEventMulticaster.java:272)
        at java.awt.Component.processMouseEvent(Component.java:6373)
        at javax.swing.JComponent.processMouseEvent(JComponent.java:3267)
        at java.awt.Component.processEvent(Component.java:6138)
        at java.awt.Container.processEvent(Container.java:2085)
        at java.awt.Component.dispatchEventImpl(Component.java:4735)
        at java.awt.Container.dispatchEventImpl(Container.java:2143)
        at java.awt.Component.dispatchEvent(Component.java:4565)
        at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4621)
        at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4282)
        at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4212)
        at java.awt.Container.dispatchEventImpl(Container.java:2129)
        at java.awt.Window.dispatchEventImpl(Window.java:2478)
        at java.awt.Component.dispatchEvent(Component.java:4565)
        at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:679)
        at java.awt.EventQueue.access$000(EventQueue.java:85)
        at java.awt.EventQueue$1.run(EventQueue.java:638)
        at java.awt.EventQueue$1.run(EventQueue.java:636)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:87)
        at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:98)
        at java.awt.EventQueue$2.run(EventQueue.java:652)
        at java.awt.EventQueue$2.run(EventQueue.java:650)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:87)
        at java.awt.EventQueue.dispatchEvent(EventQueue.java:649)
        at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:296)
        at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:211)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:201)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:196)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:188)
        at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
        at ServiceMaster.search(ServiceMaster.java:172)
        at ServiceMasterForm.searchButtonActionPerformed(ServiceMasterForm.java:262)
        at ServiceMasterForm.access$000(ServiceMasterForm.java:16)
        at ServiceMasterForm$1.actionPerformed(ServiceMasterForm.java:83)
        at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2028)
        at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2351)
        at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:387)
        at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:242)
        at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:236)
        at java.awt.AWTEventMulticaster.mouseReleased(AWTEventMulticaster.java:272)
        at java.awt.Component.processMouseEvent(Component.java:6373)
        at javax.swing.JComponent.processMouseEvent(JComponent.java:3267)
        at java.awt.Component.processEvent(Component.java:6138)
        at java.awt.Container.processEvent(Container.java:2085)
        at java.awt.Component.dispatchEventImpl(Component.java:4735)
        at java.awt.Container.dispatchEventImpl(Container.java:2143)
        at java.awt.Component.dispatchEvent(Component.java:4565)
        at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4621)
        at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4282)
        at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4212)
        at java.awt.Container.dispatchEventImpl(Container.java:2129)
        at java.awt.Window.dispatchEventImpl(Window.java:2478)
        at java.awt.Component.dispatchEvent(Component.java:4565)
        at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:679)
        at java.awt.EventQueue.access$000(EventQueue.java:85)
        at java.awt.EventQueue$1.run(EventQueue.java:638)
        at java.awt.EventQueue$1.run(EventQueue.java:636)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:87)
        at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:98)
        at java.awt.EventQueue$2.run(EventQueue.java:652)
        at java.awt.EventQueue$2.run(EventQueue.java:650)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:87)
        at java.awt.EventQueue.dispatchEvent(EventQueue.java:649)
        at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:296)
        at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:211)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:201)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:196)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:188)
        at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)

[Aditya Jha]

Dustin Schreader wrote:I usually have something there but netbeans was flagging it for some reason so I just deleted it for now. The stack trace looks different now. Why would there be a problem at line 120, I'm not even calling that method?

java.io.FileNotFoundException: ServiceMaster.csv (No such file or directory)
        at java.io.FileInputStream.open(Native Method)
        at java.io.FileInputStream.<init>(FileInputStream.java:120)
        at java.io.FileInputStream.<init>(FileInputStream.java:79)
        at java.io.FileReader.<init>(FileReader.java:41)
        at ServiceMaster.createArray(ServiceMaster.java:21)
        at ServiceMaster.search(ServiceMaster.java:166)
        ...
        ...
        ...

Never leave a catch block empty. It just increases headaches later.

As you can see in the snippet above, line 120 of class FileInputStream is called from line 79 of the same class, which has been invoked from line 41 of class FileReader, which you are using in your program at line 21 in method createArray.

The error message is printed quite clearly. Do you think you are able to track down the real problem now?

[Dustin Schreader]

Lol I wish I could see things as clearly as you. It looks like there is an issue with the file i/o with the buffer reader at line 21. I'm assuming it is the incorrect use of file i/o?

[Aditya Jha]

Your problem is not incorrect usage of api.

Dustin Schreader wrote:

java.io.FileNotFoundException: ServiceMaster.csv (No such file or directory)

What does this tell you?

[Dustin Schreader]

Oh, yup I see it now. Its not seeing the file somehow. Thanks