Everything is written up and looks good and i get no compile errors but every student object other than the default constructor has null and zero values when printed.
import java.text.DecimalFormat;
import java.lang.Math;
public class Student
{
//instantiate variables
[Code] .....
How would you display an ArrayList of Objects in a JSP page from a Servlet. Any general example would be fine as long as the example is thorough.
Each created object has more than maybe 6 or 7 properties that all need to print to the JSP.
Would you also include ways of printing it like should it be printed by using a table structure in the JSP and if so how? Things of that nature so that way it is each object has its own line and looks good. I can format it myself, I just need to know how to get it in a table for each object to print on its own row and so on...
The value is: ${object1.property1} If the value of the property is null, I want "null" to be printed, like this:
The value is: null But I get an empty string, like: The value is:
I know I can use a ternary operator, but isn't there a simpler/shorter solution? A function (like NVL() in SQL)?
The value is: ${empty object1.property1 ? "null" : object1.property1 }
Not only is this long, but the value expression is typed twice, which is a magnet for bugs.
Any compact if statement or any type of test for checking if atleast ONE out of 4 integers is null. So 1 of all, 2 of all, 3 of all, or all of them being null will give a specific result ELSE do something else.
View Replies View RelatedIs there a better way to remove null values from an array than what I have tried? This works just fine, but I just get the feeling that there is a better way to do this, without using the JCF.
private static String[] removeNullValues(String[] list){
int count = 0;
for(int i = 0; i < list.length; i++){
if(list[i] == null)
count++;
[Code] ....
I technically dont need to remove the null values for the project that I'm working on (since I just print it out and I can avoid null values with a simple statement like
if(update[i] != null) SOP(update[i])
),
but I'm just curious.
In Java is there a method which I can use to compare two Strings where in if both the values are null, they should be considered as equal?
View Replies View RelatedI'm working on a program to create a blackjack game using objects (one for card, deck. and hand). Withing my hand object I am trying to add cards to the hand but it is only adding the last card i try to add and giving null values for the the ones before.
class BlackJackHand {
private BlackJackCard [] hand;
public void addToHand(BlackJackCard c) {
if (hand == null) {
BlackJackCard [] tempHand = new BlackJackCard[1];
tempHand[0] = c;
hand = tempHand;
[Code] ....
What I want this section to do is add cards to the current hand. I was intending for it the hand to be null at first and the if(hand == null) piece to add the card the first time and then the else piece would be used when the hand already has at leas one card. I want the else section to create a temporary array that is one larger than my current hand, copy the cards from the old hand to the new hand, and then add a new card to the last space before rewriting the old hand as what the temporary hand is.
The code I am using to test if the addToHand() is working is
class BlackJackTest
{
public static void main (String[]args) {
BlackJackCard c1= new BlackJackCard(1,0);
BlackJackCard c2= new BlackJackCard(1,4);
BlackJackCard c3= new BlackJackCard(1,5);
BlackJackHand h1 = new BlackJackHand();
[Code] .....
BlackJackCard has the parameters (int suit, int value)
This should print:
ace of clubs
4 of clubs
5 of clubs
but instead prints:
null
null
5 of clubs
I have a file which contains certain positions ([a][b]) that require to be placed in a certain multi-dimensional array. For example I might have an array String[][] that is a size of 6x6 but only have values in positions [2][1] and [3][2]. Because it is important for me to maintain the given array size and also do certain actions with the given positions I cannot modify the size. In addition I need to count the surrounding neighbors each element has (including elements that are null). However because some of my further code cant process with null elements I need to remove all null elements with " " (blank).
I am not sure how this is done or if it's even possible. If it is not possible how can I do something as close as possible to my needs?
My project consists of a web app where a user can select a area from a picture and f.e. if it is a office layout he can input the worker name and any peace of hardware that the area might have. In this case there are two categories: Hardware and Computer. Hardware - it has 5 dropdown lists consisting of printer, scanner and etc. Computer - like Hardware consists of many dropdown lists which add up to components such as processor, motherboard and etc. For me, considering this is my first ever web app project, is a huge step towards web development, I have used various mixes of Java, javascript and primefaces code.
My current problem: When a user selects an area he gets a dialog box where he is prompted to select his desired input, afterwards the user clicks the 'save' button and get's another dialogbox which has a resume of what he has selected so he could check out his input and save it by clicking the 'save' button in the resume box. My problem is that when the user clicks the save button the button calls a method which takes all the input and creates an Area object (Area object consists of various objects such as: Coordinates, Dimensions, Employee, ComputerList and HardwareList) and sends a query to the database, but all the values I get is null.
XHTML code:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xmlns:ui="http://java.sun.com/jsf/facelets" xmlns:h="http://java.sun.com/jsf/html" xmlns:f="http://java.sun.com/jsf/core" xmlns:p="http://primefaces.org/ui">
[Code] ....
I am having a hard time trying to figure out how to print random numbers from a an array list. I tried google but nothing worked. I have to pick certain values from two lists and print them on the screen. I have included comments in the code to facilitate the explanation.
import java.util.Random;
public class Parachute {
public static void main(String[] args) {
Random randomNumbers=new Random();
int number;
int array []={1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21};
char A[] = {'a', 'b', 'c','d','e','f','g','h', 'i','j','k','l','m','n','o','p','q'};
[Code]...
Currently, my program converts Long values to String. And when I test it out, it do print out the correct output. However, when the converted String value is passed over to be written in a text file, it seems that BufferedWriter isn't printing out the outcome that it's supposed to be.
saltVs = Long.toString(saltV);
System.out.print(saltVs); //will print out 79723172
Now the problem is here...It only prints out the last digit of the String value (instead of 79723172).
Here is my FileWriter/BufferedWriter part.
Why is that when I run my program using command prompt, it prints out the output that I wanted, but however when it comes to writing to the file, it doesn't come out right.
Whether I pass primitives or objects the original value does not change. Is this expected result?
Java Code:
public class Class {
public static void main(String args[]) {
int x=3;
doItPrim(x);
System.out.println(x);//3
Integer i=new Integer(3);
[Code] ......
The main method should creates a Student object with name as "Bill" and marks as {88,92,76,81,83} and print it.
Java Code:
class TestStudent {
public static void main(String args[]) {
Student1 st = new Student1();
st.name = "bill";
Student st1[] = new Student[6];
//This gives error
st1[].marks = {1, 5, 8, 9, 7, 6}; mh_sh_highlight_all('java');
I've written a die program, and i want the user to type any key in order to continue, how do i achieve this ?
I have already created a Die class, i just want to implement the main method now.
PHP Code:
package test;
/* This program demonstrates the use of a user-defined class
public class RollingDice {
// Creates two Die objects and rolls them display the values.
public static void main (String[] args) {
Die die1 = new Die();
System.out.println("Roll the die ")
}
} mh_sh_highlight_all('php');
What should i add after System.out.println, So that the user types (any key, or types "Enter" for example, for the die to roll). i dont want the die to roll by itself i Want the user to interact with the program in order for it to roll.
Create an application that allows a user to enter values for an array of seven Salesperson objects. Offer the user the choice of displaying the objects in order by either ID number or sales value.
import java.util.*;
public class SalesPersonSort
{
public static void main(String args[]) {
int[] id = new int[7];
int[] salesValue = new int[7];
final int END = 999;
[Code] ....
This program is basically complete. It compiles and runs. It is a college course assignment that I pretty much completed but for the last part in which I'm suppose to change the values of all fields and display the modified values using a toString method. Modifying the values of the fields is where I am stuck. I don't think I need to create a new text data file to do this. The instructor only asked that all the values of fields be changed and this was the last part of the assignment so I don't think it involves creating additional ObjectOutputStream and ObjectInputStream objects. I'm getting a NullPointerException error on line 161.Here is the code. I'm also including the input data file.
//create program so that objects of class can be serialized, implements interface Serialiable
//create constructor with 4 parameters with accompanying get and set methods, Override toString method
//create text file with 5 records, create Scanner object,ObjectOutputStream, and ObjectInputStream
//create new ItemRecord object, change values of all fields in ItemRecord object using object's set methods
//modify ItemRecord object using toString method
[hightlight =Java]import java.io.Serializable;
public class ItemRecord implements Serializable
[Code] .....
This is the error message:
----jGRASP exec: java ItemRecordReport
Item Cost Quantity Description
Number
A100 $ 99.99 10 Canon PowerShot-135
A200 $149.99 50 Panasonic-Lumix T55
A300 $349.99 20 Nikon- D3200 DSRL
A400 $280.99 30 Sony- DSC-W800
A500 $ 97.99 20 Samsung- WB35F
Exception in thread "main" java.lang.NullPointerException
at ItemRecordReport.main(ItemRecordReport.java:161)
----jGRASP wedge2: exit code for process is 1.
----jGRASP: operation complete.
Here is the data file:
A100 99.99 10 Canon PowerShot-135
A200 149.99 50 Panasonic-Lumix T55
A300 349.99 20 Nikon- D3200 DSRL
A400 280.99 30 Sony- DSC-W800
A500 97.99 20 Samsung- WB35F
Here is the data file for the modified field values.
B100 98.00 10 ABC1010
B200 97.00 15 DEF1020
B300 96.00 10 GHI1030
B400 95.00 05 JKL1040
B500 94.00 01 MNO1050
My intention is to see the real reference values (memory locations) of 2 StringBuilder objects as below:
StringBuilder sb2 = new StringBuilder("123");
StringBuilder sb3 = sb2;
System.out.println(sb2);
System.out.println(sb3);
I was expecting a printout like
@S234853
@S984724
But all I got was 123 printed twice. How can i print out the reference values instead of what is inside the StringBuilder object ?
I'm getting an error on line 137 and all it is rsmd = rs.getMetaData();The error happens only after I press a JButton and it is
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerExceptionat softwareDesign.createAccount.actionPerformed(createAccount.java:137)
There is a lot more to it but that has nothing to do with my code it's just the stuff with Eclipse anyway I want to know how do I fix this problem?
public class Test {
public static void main(String[] args) {
Car c = new Car();
c.setInf("toyota", "red");
System.out.println("name: "+ c.brand + " colour: " + c.colour);
[code]....
Why do I get the result brand null, colour null? I know what null means but what am I missing here?
I am currently working on a project where I need to return data from a database over RMI to a client who requests it. Some of the fields in the Data Object can not be seen by the client so I need to create another object to send over the network instead. The method I use is this...
public static SerializableObject createSerializableObjectFromDataObject(DataObject dataObject){
SerializableObject serializableObject = new SerializableObject();
serializableObject.setField(dataObject.getField());
serializableObject.setAnotherField(dataObject.getAnotherField());
return serializableObject;
}
Is there a better way of doing this? I am creating many subclasses DataObject which all require this static method to be implemented and I can't push it into the superclass because each one needs custom behaviour.
I need a way to store the pixels values currently on the screen and compare them to the values on the first frame. Right now I'm using glreadpixels as follows:
currentBuffer= BufferTools.reserveByteData(mapSize);
glReadPixels(mapStartX, mapStartY, mapWidth, mapHeight, GL_BLUE, GL_UNSIGNED_BYTE, currentBuffer);
for (int i = 0; i < mapSize; i++) {
if (currentBuffer.get(i) != baseBuffer.get(i)) {
//Do nothing
continue;
}
//Do something
}
This works perfectly fine but turns out to be a real bottleneck, dropping the fps to a third of what it was. Is there any quicker way? All I'm after is speed, I don't even need to show it on the screen if the comparison is made "behind the scene".
I have a question in mind that this is my registration form. I am sending these values from HTML form to server and database. I have question that in my case if I click next to Add Another Mobile no in HTML.then a block is genereated and each time a new name is generated.
My Question is if I click 6 times then 6 name attribute are generated. How can I send and differentiate them on my server side.
Because at their I will use something request.getAttribute("Attr_Name");
But they are same. How to do this?.
how String objects are different from other objects
part 1:
// creating two objects
Dog mydog1 = new Dog();
Dog mydog2 = new Dog();
// comparing the reference variables
if( mydog1 == mydog2){
System.out.println(" The reference variables refer the same object ");
}
else {
System.out.println(" They refer to different objects ");
}
The above code works as I understand objects , it prints "They refer to different objects " to the screen.
Part - 2
// creating two objects ( I beleive, pls correct me if i am wrong )
String a = "haai";
String b = "haai";
if( a == b){
System.out.println(" Reference variables refer to same object");
When i run the above code it prints that a and b refer same object , I don't understand how they refer to same object when i didn't assign " String b = a; ". My question is did java just create one object and stored the same reference values to a and b .
I have a JScrollPane with two coulmns. In the first column I have an image pane JTable, and in the second a list with names of sections. This second column I try to divide in two columns, one (the second column) to display the names of the sections (each row contains one name), and in the other column (the third) I want to show some values for every section in the row respectively. But, instead of displaying the desired values in the third column, I get the same names of the sections as in the second column.
View Replies View RelatedSo I'm trying to add two numbers using a stack class I made myself. I have a main class with a main method in which I use three stacks on holds one number one holds the other and then I sum one digit at a time keeping in midn that there may be a carry before putting the result on a third stack.
My problem is I'm getting a null pointer error when it should be putting an integer into the top of my stack which is index 0, I've checked my code and can't see why it would be doing this.This is my main method in my main class
import java.util.*;
import java.io.*;
public class CS25driver {
public static void main(String[]args) throws FileNotFoundException {
[code]...
my input file looks like a single line of input stating the problem followed by two lines of input which need to be summed.this is the error I'm getting
Exception in thread "main" java.lang.NullPointerException
at StackClass.push(StackClass.java:38)
at CS25driver.main(CS25driver.java:55)
I've a JPanel declared as a field in a JFrame:
public static javax.swing.JPanel pane;
I initialize it in a method (Well, Netbeans' GUI builder does. :P)
pane = new javax.swing.JPanel(){
@Override
public void paint(Graphics g){
g.setColor(Color.BLACK);
g.drawArc(8, 6, 15, 15, 0, 90); /* This works. The panel and frame are displayed, the arc is drawn, &c. */
}
};
it works and all; the arc is drawn.I want to draw on it dynamically by instantiating its Graphics (I call the "public Graphics getGraphics()" method.). This has worked for me before, taking a JPanel's Graphics and drawing with it through a different method than public void paint(Graphics g); But when I do, it comes up with a NullPointerException. WAIT! Don't go rambling on about initializing the variable because I've gotten past that NPE newbie's blockade.public static void render(Something s) { /*This is in a different file altogether. pane is public, static so I can access it from here. That's not the problem.*/
JPanel jp = Frame.pane;
Graphics g = jp.getGraphics();
g.fillRect(s.x, s.y, 4, 4);
}
Upon further investigation:
Exception in thread "main" java.lang.NullPointerException
at physics.Renderer.render(Renderer.java:30) <-- This line is "JPanel jp = Frame.pane;"
at physics.Renderer.renderall(Renderer.java:24) <--This line calls public static void render(Something s)
at physics.Updater.update(Updater.java:47) <--Renderer is just a tool used by the Updater. Sounds like a game loop, right?
at physics.Physics.main(Physics.java:31) <-- The game loop.
it says that Line 30, making jp and pointing it to pane itself is the problem.
Conclusion:
-The JPanel in the JFrame is created, initialized and overrides a parent method.
-The JPanel is not initialized, meaning that it is null. There is obviously a problem.