Getting A Nullpointer Exception After Cleaning Up Code By Putting Repetitive Stuff In A Method
May 8, 2014
I am getting a nullpointer exception after "cleaning" up my code by putting repetitive stuff in a method.
The error points to this: ai.getItRight(n, answer);//make sure the user enters yes or no..
The error occurs at lines 19 and 25.Here is the relative code:
public boolean AskQuestions(Node n, String yesOrNo, String answer, String question){
if(yesOrNo.equalsIgnoreCase("no") && n.getRight() == null){//i guessed the wrong answer
System.out.println("I give up. Who is it: ");
answer = input.nextLine();
[code]....
My previous code, which use to have the contents of getItRight in place of lines 19 and 25 worked just fine. So why am I getting this error? I dont want my methods to be crazy big like how they usually end up.
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May 27, 2014
I'd like to know how to return a new array, I wrote in a method below the main method. I want to print the array but system.out.print doesn't work for arrays apparently. What structure i should use?
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Sep 21, 2014
I hope I'm putting this question in the right folder. I have an array of objects, and I have defined a setter for a variable in the object. When I call the setter, I get a NullPointerException. Here is the relevant code for the object.
public class Digit extends Thread {
private int digit;
public void setDigit(int digit) {
this.digit = digit;
}
// run method follows
}
Here is the portion of the main class where I define an array and then call the setter.
Digit[] digits = new Digit[10];
for (int i = 0; i < digits.length; i++) {
digits[i].setDigit(i); // NullPointerException occurs here
}
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Mar 21, 2015
I am creating a simple ArrayList program that would enable one to input their username to it using a scanner. However, i am getting this error: "Exception in thread "main" java.lang.NullPointerException
at home.Members.addUser(Members.java:16)
at home.Main.main(Main.java:14)"
Here is the code! :
Main.java class
Java Code: import java.util.Scanner;
public class Main {
[code]....
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Apr 25, 2015
I have problem with my simple program. I tried put some text in my text area using button1 but textListener in RighButtons is always null and it's give me NullPointerException.
WriteToArea - interface
public interface WriteToArea {
public void add_a(String text);
}
BaseFrame
public class BaseFrame extends JFrame{
[Code] .....
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Sep 15, 2014
If I put the highlighted text in try/catch block it is throwing NullPointerException , if I am using command line arguments then also it is showing the same exception.
public static void main(String []args)
args = null;
args[0] = "test";
System.out.println(args[0]);
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Dec 2, 2014
I have the following unit test that gives me a null pointer exception. The debugger goes to the finally block right after the line that creates a connection factory. Here's the test:
@Test
public void receiveMessage() throws Exception {
MessageConsumer consumer = null;
ConnectionFactory connectionFactory = null;
Connection connection = null;
Session session = null;
Destination destination = null;
[code]....
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Apr 17, 2014
I've got a nasty nullpointer that I have tried to resolve to no avail as of yet. The program should prompt for a listings.txt file and take its info and write to a report file. Here's the stacktrace:
run:
Input file: listings
Exception in thread "main" java.lang.NullPointerException
at java.io.Writer.<init>(Writer.java:88)
at java.io.PrintWriter.<init>(PrintWriter.java:113)
at java.io.PrintWriter.<init>(PrintWriter.java:100)
at kettask2b.PropertyListingsReport.main(PropertyListingsReport.java:34)
Java Result: 1
Some adjustments that I have attempted are:
BufferedWriter pwfo = null;
for (int i = 0; i < args.length; i++) {
String string = args[i];
pwfo = null;
[Code] ....
Here's the code:
package kettask2b;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileWriter;
import java.io.IOException;
import java.io.PrintWriter;
[Code] ....
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Oct 28, 2014
I'm refitting a snippet of code I found on the net to write stuff into text files. After a bit of fiddling, here's what the code looks like in one of my classes:
public void addItem(String Item){
try{
Writer out = new OutputStreamWriter(fos, "UTF8");
out.append(Item);
out.flush();
// out.close();
}
catch (IOException e) {
System.out.println(e.toString());
}
}
The original snippet included the close() method. However, when I tried to do a test run writing multiple lines, I'd get an IOException about the stream being closed. I removed the close() method line, everything seems to work the way I want it, but I just wanna know if there's anything I'm missing out on by not having the close() method anywhere, especially when the IDE finds it important enough that it lit a warning about the stream not being closed somewhere as I was repurposing the original snippet.
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May 28, 2014
I wrote a simple random spelling game for a class project, was never able to get the labels to update when they should. I have tried .updateUI, .paintImmediately followed by .revalidate and by .repaint. Nothing seems to be working.
What the game does is show a random word for about 10 seconds, disappear and they user is to spell that word, you have 3 tries then will start over. The "brains" of the game work just fine, it is the labels updating with new text when they should doesn't seem to be working. There is 4 classes but the below is the "Main" that has the problems. Also have a null exception problem with the timer.stop(); not sure why. I am still pretty new to java.
Public class SpellMe extends JFrame {
// variables
JPanel mainPanel, secondPanel, thirdPanel;
JLabel mainLabel, wordLabel;
String spWord, sp;
JTextArea guess;
[Xode] .....
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Apr 11, 2015
I am submitting on a online judge. I am getting NZEC exception in my code
this is my code
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
public class MyProgram {
static int[] arr;
static int sum=0;
static int x,y,N;
[code]...
what are the causes that is showing NZEC to me?
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Mar 5, 2015
This is my code
import java.util.ArrayList;
import java.util.Scanner;
public class Main {
private String[] inputStrings;
private ArrayList<InputField> decodedMessage;
public static void main(String[] args) throws Exception{
new Main().solve();
[Code] ....
This is giving me NZEC exception.I am testing this solution on a online judge.So I don't have any TestCase in which this is failing. So, what are the possible reason of NZEC exception in my code?
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Feb 27, 2015
I am trying my code which catches exception when mismatch variable is inputed as i read it with Scanner. It seems right for me but whenever i run it, it keeps leaking memory or something like that
Code :
import java.util.*;
public class Exercise10_1 {
static Scanner scanner = new Scanner(System.in);
public static void main(String[] args) {
boolean exception;
do
[Code] .....
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Feb 13, 2015
So I'm learning java having been using c#. I based this code off an example from class. It compiles fine with no errors, but I'm getting this:
Which model do you want? + Standard,Electrum,CurveHilted, or Tonfa Standard
Exception in thread "main" java.lang.ClassNotFoundException: Standard
at java.net.URLClassLoader$1.run(URLClassLoader.java:366)
at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
at java.security.AccessController.doPrivileged(Native Method)
[Code] .....
How/where to point the correct class.
package com.company;
import com.sun.java.util.jar.pack.*;
import java.util.Scanner;
class LightSaberFactory {
static LightSaberFactory lsf;
ChooseLightSaberColor saberColor;
[Code] .....
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Dec 8, 2014
It doesn't work and I always get UnknownFormatConversionException...
public class studentPoll {
{
public static void main( String[]args)
{
int[] responses = { 1, 2 , 5, 4, 3 , 5, 2, 1 , 3, 3, 1, 4, 3, 3, 3,
2, 3, 3, 2, 14 };
[Code] .....
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Jun 30, 2014
I got a strange (!?) behavior using an FXML annotated object ...
Consider the following:
You got an app with FXML build UI.
There is a button called connectB which is @FXML annotated...
In the initialize method of my app I disable this button.
After the startup of my app I want to connect to a DB ...
Therefore I use an Task<Void>
I put everything together in one class ( the main application class )
Here is the code...
public class MainApp extends Application implements Initializable{
// ... several other objects
@FXML
private Button connectB;
@Override
public void initialize( URL location, ResourceBundle resources ) {
connectB.setDisable( true );
[Code] .....
The connectB is not null in the initialize method but later in the task class ....
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Mar 19, 2015
I am practicing OCPJP ....
import java.lang.*;
class InvalidValueException extends IllegalArgumentException {}
class InvalidKeyException extends IllegalArgumentException {}
class BaseClass {
void foo() throws IllegalArgumentException {
throw new IllegalArgumentException();
[Code] .....
Which one of the following options correctly describes the behavior of this program? And the answer is (definitely) --> The program will print : InvalidKeyException exception, but when i saw the explanation, it tells
It is not necessary to provide an Exception thrown by a method when the method is overriding a method defined with an exception (using the throws clause).
I don't know, but i think it will compiled because the Exception that is thrown by the foo method in DeriDeri class is inherited from unchecked exception.. so it is not necessary to declare throws statement on its method.. and if the exception was checked exception the answer must be different right?
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Aug 15, 2014
I have a file greenGrow.txt, and every three lines of the file has a last name, first name, and yard size. Every time a Customer object is created, I need to read the file 3 lines and assign the object a last name, first name, and yard size.
Snippet of my code:
import java.io.*;
import java.util.*;
public class Customer {
private String lastName;
private String firstName;
private int yardSize;
[Code] .....
My issue is that I cannot call readFile() from the constructor, and I'm assuming that's because I throw Exception on readFile(). Is this a simple fix, or am I looking at it the wrong way?
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Aug 31, 2014
The 2 minute drill from page 69 SCJP kathy and bert book, says regarding Interfaces, that - "A legal nonabstract implementing class must not declare any new checked exceptions for an implementation method."
When I try the below given code in eclipse , it does not throw any errors . (Here I have tried to throw NullPointerException from testFunc whereas the interface function throws IllegalStateExc)
package abstracttesting;
public class StaticCheck implements check{
public void testFunc() throws NullPointerException{
// TODO Auto-generated method stub
} public static void main(String[] args) {
// TODO Auto-generated method stub
}
}
interface check{
void testFunc() throws IllegalStateException;
}
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Mar 19, 2015
I'm trying to call the grade.processFile method from the main method but I'm getting this Error below. I'll post my code which includes the main method and the class underneath the error message:
Exception in thread "main" java.lang.NullPointerException
at java.io.FileInputStream.<init>(FileInputStream.jav a:130)
at java.util.Scanner.<init>(Scanner.java:611)
at MyGrades.processFile(MyGrades.java:49)
at myGradesMain.main(myGradesMain.java:19)
import java.util.Scanner;
import java.io.*;
[code]...
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Jan 8, 2015
The error I get when I execute my java file.
Exception in thread "main" java.lang.NullPointerExceptionat DogTestDrive.main(DogTestDrive.java:19)
Here is the source
class Dog {
int size;
String name;
void bark () {
if (size < 60) {
System.out.println("Woof woof");
[code]....
Some background: I'm reading "Head first Java 2nd edition" and I'm going through the examples which is showing me how to change the state of an object. The original code looks like the code below, however the previous chapter went over creating array's of an object, so I created an array of the object "Dog" and wanted to re-write it this way. To my understanding, it should work but it's giving me that error when I execute it. The error itself isn't very clear, if I could get a line number pointed to, that would work.
class Dog {
int size;
String name;
void bark() {
if (size > 60) {
System.out.println(“Wooof! Wooof!”);
} else if (size > 14) {
System.out.println(“Ruff! Ruff!”);
} else {
System.out.println(“Yip! Yip!”);
[code]....
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Mar 3, 2015
I am having trouble putting an int value into an array. The error code I get at compile time is this: "error: array required, but int found". The following is snippets of my array initialization and the line producing the error.
int[] fitness = new int[POPULATION_SIZE];
int fitness = 100;
Next, the line where the problem occurs. In this code "i" is an int variable that represents a place in the array fitness (this part of the code is within a for loop).
fitness[i] = fitness;
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Mar 6, 2015
I need to access a method from a dll in java as below and is giving an error
"Exception in thread "main" java.lang.UnsatisfiedLinkError: Testdll.Decrypt(Ljava/lang/StringLjava/lang/String;
at Testdll.Decrypt(Native Method)
at Testdll.main(Testdll.java:31)
"
I have included the jna-4.0.0.jar and the HashMatchCryptography.dll to the project in eclipe and the java-library-path has the path for the lib
import com.sun.jna.Library;
import com.sun.jna.Native;
import com.sun.jna.NativeLong;
import com.sun.jna.Platform;
import com.sun.jna.*;
import java.lang.*;
[code]...
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Apr 9, 2014
I have a 2D array and the elements are listed as follows:
outlook temperature humidity windy gooutside
sunny hot high false n
overcast hot high false y
....
I need to put these values into a HashMap, where the elements of the first row are the keys and the elements from row 1 to n-1 are the values. What would be the best way to make sure the key and values are matched correctly?
Here is what I have:
String[][] array = new String[numberOfRows][numberOfCols];
HashMap<String, String> map = new HashMap<String, String>();
for(int rows = 0; rows < (numberOfRows * numberOfCols); rows++) {
for(int cols = 0; cols < array[i].length; cols++} {
map.put(array[0][cols], array[rows*cols][col];
}
}
I keep getting the out of bounds error.
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Jul 3, 2014
I am trying to add buttons in a loop to my but when i compile my program i can`t see my buttons. I can see other stuff that added to jpanel ...
static JButton blocks[][];
for (int i = 0; i < block.length; i++) {
for (int j = 0; j < block[i].length; j++) {
block[i][j] = new Block(i, j);
blocks[i][j] = new JButton(i+"");
blocks[i][j].setLayout(new GridLayout((i+1) * 10, (i+1) * 10, 10, 10));
pageAxisPanel.add(blocks[i][j]);
}
}
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Apr 15, 2014
I'm trying to read user input from the terminal and separate the input into separate arrays depending on if the user input is an integer, scanner, or a string. The terminal should keep asking the user for input until the user types "quit".
import java.util.*;
public class arrayScanner {
public static void main(String[] args) {
ArrayList<Integer> intList = new ArrayList<Integer>();
ArrayList<Double> doubleList = new ArrayList<Double>();
ArrayList<String> otherList = new ArrayList<String>();
[code].....
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