Ok say you have
public class MyClass {
private int x = 5;
Object myObject = new Object();
public MyClass(){
}
}
When would the myObject be created? Before or after the constructor? And does this mean you can't pass
this into the parameters of that object?
I know that I can declare and initialize an member variable inside a class in a single statement but I can't do them on separate sentence. Why?
For example, I am allowed to do the following,
class A{
int a = 5;
// rest of the class
}
But I am not allowed to do this,
class A{
int a;
a = 5; // it doesn't compile even when the variable 'a' is static
// rest of the class
}
Why java don't allow me to do that?
The experiments will slowly converge towards one big experiment: a simple game. I have just a little interest in games (perhaps I should have more), but making one - even a simple one - should be self rewarding.
However, now to the point.
* The experiment creates an array of rectangle objects.
* The rectangles are painted inside a Frame object at random x,y coords generated by a random number generator
* The rectangles are stationary.
* The rectangles are each assigned their own random colour.
* The array of rectangle objects is created inside the constructor of the class.
The actual code contains various other variables and methods which would distract from a quick analysis, so below is code which has the same logical structure which also fails (instead of array of rectangles, I have used arrays of integers).
import java.util.Random;
/**
* Experiment 14 - see if it works simply - (with integer arrays)
*/
public class TestingArrays {
// instance variables
int N = 10; // the size of the array - 10 elements
int[] a;
[Code]...
I am developing a java based software connected with a mysql database. I have an Item table in my database. I created a bean class which can keep all item data with it and. Then I loaded each Item data in to its object and fill a Jcombobox. Now I want to search with Item name and get all Item data when selecting that item. I have overidden the toString method to Item name in that class. Is there any way to search my Item objects inside a jcombobox?
View Replies View RelatedI am trying to place a number of JLabel and JTextField objects inside a JPanel which has a JScrollPane.
One thing is, that at one time, I have have a certain number of JLabel and JTextField objects which number would cover an area greater than the JPanel's vertical size.
How when I implement the JScrollPane and I run the program, the scroll bars appear, but they don't scroll the pane inside the JPanel, the items are fixed.
Could the problem be because I am using a Null Layout.
Will I have to use one of the standard layouts available, like GridLayout for the JScrollPane scrolling function to work?
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.
How do you declare methods for a class within the class whilst objects of the class are declared else where?
Say for instance, I have a main class Wall, and another class called Clock, and because they are both GUI based, I want to put a Clock on the Wall, so I have declared an instance object of Clock in the Wall class (Wall extends JFrame, and Clock extends JPanel).
I now want to have methods such as setClock, resetClock in the Clock class, but im having trouble in being able to refer to the Clock object thats been declared in the Wall class.
Is this possible? Or am I trying to do something thats not possible? Or maybe I've missed something really obvious?
I will give an example below of what I am talking about. in C++ I know I would need a copy constructor because I would be pointing blindly in the heap if I deleted a object in the struct.
We have a Class/struct animal and three animals in that class/struct, a dog, a cat and a cow. Each animal has a baby and then I will give the animal a name in main. But if I delete one of the dogs puppies because I sold him wouldn't I being pointing off in the heap and have a leak?
Also since Java doesn't have structs can I put a class inside a class?
I have to modify my ContainerImpl.java inside a .jar file. My modification is in here: [URL] but I do not know how can I modify it
View Replies View RelatedI am not able to understand how we are able to create an object of static inner class defined inside an interface .
interface outer {
class inner {
void disp() {
System.out.println("inside disp");
[Code] ....
output:
inside disp
How am i able to create a new object for static class?
Can a class be defined inside an Interface .
interface Inter{
class x{
public static void main(String[] args){
System.out.println("Hello World!");
}
}
}
I have a doubt regarding to java.
Can we declare a class inside an interface?
Ans :yes
But what will be the situation?
I am not getting why it is required...........
What this interface inside that abstract class does. Looking for some examples to how can i use it ....
public abstract class Expression {
public abstract String toString();
public abstract SimpleExpression evaluate();
public void show() {
System.out.println(this + " = " + evaluate());
[Code] ....
I am puzzled by a note in the book I am reading (by Mala Gupta). Page 55 says "All java components you've heard of can be defined within a java class: import and package statements, variables.....". But the online oracle doc (tutorial) clearly says the following 2 statments:
"If present, package statement must be the very first line in a file"
"To import a specific member into the current file, put an import statement at the beginning of the file before any type definitions but after the package statement, if there is one. " (Here).
So, how can import and package be present inside a class ? (This seems to go against the 2 statements from oracle online tutorial).
I'm trying to access class file which is inside the package and package is inside the jar file but I can't access that class file inside my source file . All files are on desktop .
View Replies View RelatedI saw an example where an (inner)class is declared inside the main method, this is correct or not and why/when it's reasonable to use?so smth like this
public class myClass()
{
public static void myMethod(myInnerClass obj)
{
if (obj.method())
[code]....
How do I create an instance of a class in a method?
I am a bit rusty whenever I think of instances. I always think of main method and objects when I see instance which gets me confused on what to do when I am not in a main method. The example:
I have a abstract class, School, and inside School I have some methods that must preform some action on an instance. For example, there is a move() method that must move the instance of School. Another method named, personOld(), which returns whether or not an instance of School surpassed some determined age.
How do I do this and create this instance?
this code won't compile because selected row must be declared as final because of it being defined outside the window listener. Is their anyway around this? If I make it final the first time that the variable is called it keeps it starting value until the GUI is closed.
butEdit.addActionListener (new ActionListener () {
@Override
public void actionPerformed (java.awt.event.ActionEvent evt) {
int selectedRow = table.getSelectedRow ();
final String [] values = custTableModel.getRowValues (selectedRow);
[code]....
I know that the simple deployment using only applet tags inside HTML causes severe security restriction for the applet on the client side. but can this simple HTML file contains .jar files inside the applet tags instead of .class files.
View Replies View RelatedCreated a java.sql.connection object. Refering those obj inside public void run() { } If i declare as final inside a method, i can't refer those outside method due to scope. Cannot refer to a non-final variable dbConnObj inside an inner class defined in a different method...
View Replies View RelatedCan we write java class or code inside Oracle Stored procedure.
View Replies View RelatedI have an application which is doing a fine job of placing the total hours on the interface.
Where I am breaking down is that I am unable to split the string into two distinct groups: hours and minutes
private HtmlElement createTravelTimeRow(ShowSet showSet) {
HtmlElement tr = new HtmlElement(ROW_OPEN, ROW_CLOSE);
HtmlElement td = new HtmlElement(CELL_OPEN, CELL_CLOSE);
[Code].....
I came across something which showed how to split the String but I am still very unsure how to do this.
how to refer to objects die1 and die2 in the PairofDie class from the SnakeEyes class and what to do.
public class Die {
private final int MAX = 6;
private int faceValue;
private int sum;
//private int faceValue2;
public Die(){
faceValue = 1;
[code]....
I have a class which connects with database and fills object with data. Method looks like this:
//in database class
void getData(anObject a, int id){
//connects with database
a.field1=get...
a.field2=get...
....
//disconnects
}
Now I want to use this method in anObject class, but I can't call it because I don't have created object jet. Is there any way to call this method?
So I'm still trying to get to grips with Java, and like to understand exactly why I'm doing something, so that I am not just regurgitating the code, If I want to create an object from class "Apples", I would use the following, right?
Apples MyAppleObject = new Apples();
From what I understand, MyAppleObject is the new object name, new -> creates a new instance of it in memory, and Apples() is the onCreate method that is called
So question 1: (just a quick aside question) Can I create an object without calling Apples()? i.e.
Apples MyAppleObject = new;
Question 2: - PARTLY SOLVED - I discovered that (Button) is a way of typecasting, so I understand that line a little better. What I don't understand is why we don't need to initialize the object with "new"
I've now looked at a bit of android development and xml and those declarations are all together different, and I'm not sure why. I haven't found a single explanation for the difference in format.
Java Code:
Button Add;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Add = (Button) findViewById(R.id.button1); mh_sh_highlight_all('java'); So the Button object is declared above the onCreate method, but initialized afterwards I guess....
But instead of using Button Add = new Button() they use Add = (Button) findViewById(R.id.button1);
Question 3:
then In XML they use the following:
Java Code:
public*static*void*main(String[] args){
*********
********// Creates a DOM object in memory. Now you can access
********// data in the xml file
*********
********Document xmlDoc = getDocument("./src/tvshows5.xml"); mh_sh_highlight_all('java');
Once again, why didn't they have to use : Document xmlDoc = new Document()
Having trouble adding Class (Dollar) objects to a HashSet (money), i have done this before with arraylists and i understand that HashSets are different in that they cannot contain duplicates. Currently when this code is compiled i am getting "null" printed when I run the "howFullDatWallet" method.
import java.util.*;
public class Wallet {
private HashSet<Dollar> money;
private int walletSize = 0;
private int walletFiller = 0;
/**
* Constructor for objects of class Pocket
*/
public Pocket(int walletCap)
[code]....