String Object In Class - NullPointerException
May 18, 2013
I have a little a problem with String object in this class ....
public class Personne {
private String nom;
private String prenom;
private int age;
public Personne(){
this(null, null, 0);
[Code] ....
When i call the class personne with the Personne() i get these errors in compiling-time :
Exception in thread "main" java.lang.NullPointerException
at java.lang.String.<init>(Unknown Source)
at Personne.setNom(Personne.java:18)
at Personne.<init>(Personne.java:12)
at Personne.<init>(Personne.java:8)
at Main.main(Main.java:4) // The line wich i inisialize my object in my main method.
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Mar 1, 2014
I am having some problems with some code and I need an extra set of eyes. It appears I've missed something. I am getting a NullPointerException with a Hashtable object, which I can clearly see I've created. So I'm not quite sure why it is happening. I am pretty sure it is do with the code I've posted because I've tested everything else involved.Here is the code where it happens,
Java Code:
public void siteGen(String user, String site)
throws ExcGenDatabad, ExcSiteNodomain, Exception {
System.out.println("calling siteGen, user: " + user + ", site: " + site);
String nginx_template;
String fpm_template;
[code]....
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Oct 22, 2014
why my sub class object just gives me a blank when it comes to the String. It works just fine for the super class but when I get to the sub class the program just gives me a blank. I won't let me input anything for the String. On line 24 of the client I attempt to input a new String but it doesn't ever let me enter one so then any call to getName is just a blank.
I have altered my super and sub class as well as the client to try to get it to work. I tried a local variable in the client, I tried using protected in the super class, I tried a handful of other things.
import java.util.*;
public class TryingItOutClient {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
[code]....
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Dec 13, 2014
Assuming that we have two classes B and C which inherit from class A. What is the best way to pass a parameter from an object of class B to an object of class C by the use of class A without using static variable and without defining a get function in B?
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Apr 8, 2014
Suppose you have a generic Dog class of the pet type that implements a DogInterface of the pet type. What is the difference between;
DogInterface<pet> Rex = new Dog<pet>();
and
Dog<pet> Tye = new Dog<pet>();
In what situations might you want to use Rex instead of Tye?
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Mar 24, 2014
"You might wonder what happens when a static synchronized method is invoked, since a static method is associated with a class, not an object. In this case, the thread acquires the intrinsic lock for the Class object associated with the class. "What is a Class object associated with a class. Google search rather finds material about the Object class.
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Feb 4, 2015
I want to know is there any way we can call parent class method using child class object without using super keyword in class B in the following program like we can do in c++ by using scoop resolution operator
class A{
public void hello(){
System.out.println("hello");
}
}
class B extends A{
public void hello(){
//super.hello();
System.out.println("hello1");
[code]....
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Aug 28, 2014
can we pass private final class object to another class constructor?
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Apr 22, 2015
How to create object for "class B" and call the "function_B" from other different class D where class D has no connection with class A? Here is my program.
public class A(){
void print(){}
}
class B{
void function_B(){}
}
class C{
void function_C(){}
}
Here, A, B, C are in the same package. But class D is in different package.
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Nov 16, 2014
I am a beginner here at JAVA and I am trying to program a Gratuity Calculator using both interface class and object class but it keeps on compiling with errors saying "cannot find symbol".I tried everything to fix it but it just keeps on stating symbol.
[CODE]
public class GratuityCalculator extends JFrame
{
/* declarations */
// color objects
Color black = new Color(0, 0, 0);
Color white = new Color(255, 255, 255);
Color light_gray = new Color(192, 192, 192);
[code]....
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Jun 10, 2014
Design a class named Person and its two subclasses named Student and Employee. Make Faculty and Staff subclasses of Employee. There is also a MyDate class as explained below. A person has a name, address, phone number, and email address. A student has a status (freshman, sophomore, junior, or senior). Define the status as an integer which can have the value 0 (for "Freshman"),
1 (for "Sophomore"),
2 (for "Junior"), and
3 (for "Senior"),
but don't allow the status to be set to any other values. An employee has an office, salary, and dateHired. The dateHired is a MyDate field, which contains the fields: year, month, and day. The MyDate class does not explicitly inherit from any class, and it should have a no-arg constructor that sets the year, month, and day to the current year, month, and day. The MyDate class should also have a three-argument constructor that gets three int arguments for the year, month and day to set the year, month and day.
A faculty member has office hours and a rank. Define the rank as a String (for values like "Professor" or "Instructor"). A staff member has a title, which is also a String. Use data types for the fields as specified, or where one is not specified, use a data type that is appropriate for the particular field. Write a test program called TestEveryone.java that creates a Person, Student, Employee, Faculty, and Staff object, and invoke their toString() method (you don't need to call the objects' toString() method explicitly).
Note: Your MyDate.java class is the object class that your dateHired field is created from in the Employee.java class.
Do not use the Person, Employee or Faculty classes defined on pages 383 and 384 of the book. Create new ones.Here is the code I have so far concerning the employee and MyDate.
public class Employee extends Person {
private String office;
private double salary;
//private MyDate dateHired;
//7 argument constructor for employee
public Employee(String name, String phoneNumber, String email, String address, String office, double salary /*MyDate dateHired*/) {
super(name, phoneNumber, email, address);
[code]....
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May 20, 2015
In the process of creating a new class, I need to move my main method from the class SaveDate to the class DynamicTest. Below I have listed the code of both classes.The objective is to be able to run my program from the DynamicTest Class. I need understanding the process of moving my main method to a different class and creating an Object of a class and calling its method.
public class SaveData {
private static final Map<String, Object> myCachedTreeMap = new TreeMap<String, Object>();
public static final List<String> getLines(final String resourceParam, final Charset charset) throws IOException{
System.out.println("Please get: "+resourceParam);
if (myCachedTreeMap.containsKey(resourceParam) ) {
// Use the cached file, to prevent an additional read.
[Code] ......
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Sep 22, 2014
I have a value object class and it has the below member
XMLDocument request = null;
Should I instantiate it in the VO class as
XMLDocument request = new XMLDocument();
or leave it null and let the calling program instantiate it?
What's the proper way to do it for Value Object classes in java ?
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Dec 16, 2014
i am trying to write a class method which will take in a string and returns a string which is the reversed version of that string. it compiles fine but when i try to run it it states Main method not found in class StringReverse,please define the main method as public static void main(String[]args). I am new to java and cannot figure out
import javax.swing.JOptionPane;
public class StringReverse {
public String reverseString(String str){
JOptionPane.showInputDialog(null,"Please enter word");
char c = str.charAt(str.length()-1);
if(str.length() == 1) return Character.toString(c);
return c + reverseString(str.substring(0,str.length()-1));}}
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Mar 31, 2014
I want to write an app that declares a class Person(String name, int age), and an Account class, Account(int code, double balance).But, additionally, every Person has at most 3 accounts, and each account has a Peron associated with it.
my code so far...
public class Person {
private String name;
private int age;
private Account[] accounts;
private int numOfAccounts;
public Person(String name,int age){
this.name=name;
[code]....
My problem is:When I make data input for a person, and additionally I want to read data for the account(s) that this rerson has, what code should I write to create a new Account object as account[numOfAccounts].And, what is the code to assign an owner to a new created Account object?
There exists a relationship between the two classes, but I cannot find the way to implement this relation....
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Apr 21, 2015
I am doing a project for my Java class but I ran into a snag with my code.
package lesson13;
import java.io.FileNotFoundException;
import java.util.LinkedHashSet;
import java.util.Set;
public class CharCountingStudy {
public static void main(String[] args) throws FileNotFoundException{
Set<FileExaminer> examiners = new LinkedHashSet<>();
examiners.add(new FileExaminer("raven.txt"));
examiners.add(new FileExaminer("jabberwocky.txt"));
[Code] ....
I keep getting a NullPointerException at the "examiners.add(new FileExaminer("raven.txt"));", the "calculateCharCountAlpha();", and the "if (charCountAlpha.containsKey(w)){"and I don't know why it is doing that.
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Jun 13, 2014
I am trying to get a price of a certain show in a theatre but the problem is that i don't know how to use the method's String parameter:
/**
* Gives the price of the show with a given place in the room
*
* @param place the place in the room (VIP, average seating, in the back)
* @return price
*/
public double getPlaceprice(String place) {
if (place !=null) {
double p = place.getPrice();
// price= Double.parseDouble("place.getPrice()");
return p;
}
return 0;
}
Now I have a class called Place which has an attribute double price and a getter for price
public double getPrice() {
return price;
So I somehow have to alter the String parameter Place to the object(class) Place, on which i can call the method getPrice()
At least, that's what i think i have to do. Where i go wrong?
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Oct 23, 2014
I am getting a NullPointerException Error and I cannot seem to figure out what is causing it. I am reading in a grades1.dat text file and putting the values into a 2D array. The error is occuring in my addGrade method, but I am not sure what the error is. Here are the values for my grades1.dat that I am running in through Run Arguments in JGRASP.
Student1
5
a Activities 0.05
q Quizzes 0.10
p Projects 0.25
e Exams 0.30
f Final 0.30
a100 a95 a100 a100 a100
q90 q80 q100 q80 q80 r90
p100 p95 p100 p85 p100
e77.5 e88
f92
Here are the errors that I am getting.
Exception in thread "main" java.lang.NullPointerException
at GradeBook.addGrade(GradeBook.java:114)
at GradeBookApp.main(GradeBookApp.java:55)
import java.util.Arrays;
/**
* Stores students name, a char array of category codes, a String array of categories, a double array of category weights, and a two dimensional double array of grades where each row contains all the grades in a particular category.
[code]....
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May 3, 2014
I have been playing around with my code, but how to avoid NullPointerexception.. So my program's point is simple, use Jsoup to scrape html of certain webpage, then i search the things i want and print them out. Problem is, when scraped html doesnt contain even 1 thing on my search list, i get NullPointerException... i understand why, Heres part of my code:
Java Code:
//Things i need to search from html
String[] MySearchArray = new String[]{"138","146","474"};
//Search things contained in MySearchArray and print them out
for (String Ml : MySearchArray) {
Element flights = doc.select(String.format("tr:contains(%s)", Ml)).first();
Elements flights2 = flights.select("td");
System.out.println(flights2.get(4).text() + " " + flights2.get(0).text()+ " " + flights2.get(3).text());
} mh_sh_highlight_all('java');
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Sep 28, 2014
this is part of a larger project but i figure if i can figure out this first step i can work the rest. I need to get a title from the user add it to a object array (i think thats what it is) and then when i call listAllItems(), items[] should be copied into a string array called listAllItems, and then printed, but currently im jusst having trouble i think making it an object and then make it an item in the items[], if i run case 3 the list it says null...
public class MediaItem {
String title;
MediaItem(){
}
MediaItem(String title){
[Code] ......
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Aug 20, 2011
I want to store a String.split("seperator") to a Set<String>.
Example:
Java Code: Set<String> = (Set<String>) "a|b|c".split("|"); mh_sh_highlight_all('java');
Sadly String[] and Set are incompatible types.
About the same as using .add three times, but shorter.
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Dec 3, 2014
I have the following method that I need to implement:
{
// YOUR CODE HERE
File file = new File(filename);
int counter = 0;
String tempArtist, tempName;
Album tempAlbum;
Track tempTrack;
[code]....
Ok so I updated my code from the initial post since I made some progress on my own. I guess now I'm just stuck on how to scan in the file of strings and stock it into the type Track. (I've tried using both the initial linked list for this and a temporary variable with no luck).
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Feb 4, 2014
I'm preparing for an exam in a course focusing on algorithms, code:
Java Code:
protected static class Node<E> {
public E data;
public Node<E> left;
public Node<E> right;
[code]...
Are they objects of their own class?
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Feb 19, 2015
I run a bash command and save the output as a string object
String str1 = "" +getLastOutput();
str1 would look like this: abcd efgh lkmn xsds
In this string ( str1) i need to check three separate words are there.
If i have an if statement with str1.contains("xyz") && str1.contains("lkmn") &&str1.contains("zzzzzzzzzzzz")
How can i get the one that is not there returned to the screen? so i can use elsewhere?
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Feb 13, 2014
I am converting String to date object while converting this i am getting Run time Exception. Here in this code i am using String tokennizer reading a data from a text file. Here is my code
public static void main(String[] args)throws Exception {
FileReader fr = new FileReader("g:abc.txt");
BufferedReader br = new BufferedReader(fr);
String line = br.readLine();
[Code] .....
here is an text file which i am reading
priyaRaoDBA13-APR-6002-JUN-92MahdipatnamHyderabad01-FEB-93 -AdminFpriyaM784223680212348
ArifRizwanDevelopment14-FEB-8812-MAR-12Sathya coloneyHyderabad10-FEB-14 -Software EngineerMasdfghManager7842655502123
AFifRizwanDevelopment14-FEB-8812-MAR-12Sathya coloneyHyderabad10-FEB-14 -Software EngineerMasdfghManager7802655502123
AsifRizwanDevelopment14-FEB-8812-MAR-12Sathya coloneyHyderabad10-FEB-14 -Software EngineerMasdfghManager7842631102123
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Nov 15, 2014
I woud like to convert a string(which is in an array) to a custom object.
Also, if I have different custom objects, will it be ok if I use
ArrayList<Object> o = new ArrayList<>();?
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