if I declare
class Example
{
int x=10;
......
}
It is not showing any error but when I declare
class Example
{
int x;
x=10;
............
}
it showing compile time error ....
From the tutorial:instance variables can be declared in class level before or after use.But the code below does not compile. Why?
Java Code:
public class MainApp {
i=5;
public static void main(String[] args) {
System.out.println("Hello World");
}
int i;
} mh_sh_highlight_all('java');
As web server has multiple threads to serve client requests in Thread Pool & to ensure Thread Safety we should not use any variables or Objects at Instance/Class level.But in case of Session Variable which one is the Best Practice as the Session object is used by all the requests to have the same Session ID.
My Code :
public class MyServlet extends HttpServlet {
private static Logger log = Logger.getLogger(ClientRegistrationServlet.class);
private HttpSession session; /* This is used at Instance Level*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
[code]....
I come from a C++ background and I recently started learning Java from "Thinking in Java" 4th Edition by Bruce Eckel.What's the difference between:
// explicit in class initialization
// saw this on page 126
class A {
}
public class B {
A obj1 = new A();
A obj2 = new A();
}
and
// non static instance initialization
// saw this on page 132
class A {
}
public class B {
A obj1;
A obj2;
{
obj1 = new A();
obj2 = new A();
}
}
Can we set the class path for one level down the current directory? My structure is like
binlibresourceshexicon.cmdinside the folder dist.
In this case I could run the .cmd file which has java -cp .;lib;resources client.Test .
c: rycpdist>java hexicon.cmdBut if i put the .cmd file inside bin as like this and run as
c: rycpdistin>java hexicon.cmdI am getting this error Error: Could not find or load main class
Is there any possibility to set the class path in this case
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?
Does child class gets a copy of the methods and variables of parent class?
public class test1 {
public static void main(String a[]) {
Child c = new Child();
c.print();
[Code] ....
why is the output 1?
I just want to be able to read type and weight in the Letter class I created (I created read out messages to check in the Letter class). I am able to read it with in the Mail class.
package org.mailprice.postage;
import java.util.Scanner;
public class Mail {
static Letter letter;
[code]....
I will like to add to the questions about constructors and its this. I have a class A with a constructor, i have a class B which initialize the constructor. also i have a class C which needs a variable in class A but doesn't need to initialize the constructor of A. the question how do i access the variable of class A without initializing the constructor.
View Replies View RelatedI wanna know which is the best way to access a variables within a class ...
Using direct access or using the variable accessor ...
Example :
public class Numbers{
private int n1;
private int n2;
public void setN1(int n){
n1 = n;
[Code] ....
This program should create a GUI that has 5 classes together on a grid layout. The problem that I am having is that the user input class has the input for kwh, hours, and gallons. I am having problems getting that information from the user input class to the totals class.
user input class:
package applianceutilitycalculator;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.Scanner;
import javax.swing.*;
[code].....
The totals class should take the info from the kwh hours and gallons and do the math to get a total and display it in a JTextField(?).
When creating a class with a constructor, why does one have to create private variables (attributes) to be used as parameters by the object? The object's parameters will be set to be exactly equal to the private variables (attributes), so what is the point of having the private variables (attributes) Why are both private variables (attributes) and parameters needed when they are set to be equal each other anyway?
View Replies View RelatedI write a small program. I want post my integer variables in the next class. Here a code(I wanna change answer color):
Main class(pagrindine.java):
import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
import javax.swing.event.*;
//Mokinio rinkinukas su skaiciofke kur gali keisti atsakymo spalva, pabandyti sukurti uzrasu knygute.
[code]....
So, I want to post variables r,g,b from class slideris.java in the pagrindiness.java.
I have An Issue With My Java Applet. Im Trying To Share My Variables With Another Class, But Its Not Working.
Class 1
package com.Tobysmith10.game.main;
import java.applet.Applet;
import java.awt.Graphics;
public class Game extends Applet{
public void init(){
setSize(850,480);
public void paint(Graphics g){
g.fillOval(x,y,20,20);
}
}
Class 2
package com.Tobysmith10.game.main;
import java.applet.Applet;
public class gameLoop extends Applet implements Runnable{
public int x, y;
public void run(){
while(true){
x = 100;
y = 100;
}
}
}
So im sharing the x and y variables with the Class 1 , but I get yellow lines under it and when i run the program, it crashes, how do I get class 1 to recognize the variables from class 2 ?
I am having some problem accessing variables from an array instance of a class. Heres what i have done;
In the main class:
Example obj[]= new Example[4];
In the main class constructor:
obj[0] = new Example(0);
obj[1] = new Example(1);
obj[2] = new Example(2);
obj[3] = new Example(3);
In the main update() method:
if(condition)
//update
In the Example class constructor:
private boolean change = false;
In the Example class update() method:
if(x >20)
change= true;
Now, i want to access the variable change from the main class, how do i do it? The 'condition' in the if statement is the condition of wether the change variable ia true or false. How do i access it?
I have to create an application that deals with maps.
I first have to create the instance variables for the class.
So very simply if my hashmap is going to consist of football clubs and players. Football clubs being a string value for the key and players being a set of strings for the values. How would I go about creating the instance variable in a class for this?
I can't seem to find anything that specifically deals with instance variables and constructors for maps.
how to get access from variables in a super class or a subclass. Here is what I got:
1) I have a super class that is in Jar file, I created a link in Eclipse, I know that the link is created correctly, I am going to concentrate just in one variable, so I don’t have to put all the code here firstName; in the super class(the one that is define in the path)
public class CommissionEmployee {
// Field descriptor #6 Ljava/lang/String;
private java.lang.String firstName;
in my class i have 6 argument constructor
I have a school assignment that involves me sorting an array of objects based on one of the class String variables. I am using as the title says a simple selection sort method. The problem I'm having is that when I run the program in debug mode, it never seems to enter the if statement in the inner loop. I would like to say I've tried a number of things to figure it out, but honestly I'm just stumped as to why it's not working.
Here is the code:
public static void sortTransactions(Transaction[] oTransaction){// This is the sorting method, obviously it's not done so it currently just prints to screen.
System.out.println("Successful call to sortTransaction()");
String min = "";
int curInd = 0;
Transaction[] temp = new Transaction[1];
[Code] ....
The output when I check to see if the array is sorted verifies that the array never does get sorted.
I am very Java illiterate and I need to know how would i set all the variables in the first class to null or 0 to make a new method to clear everything.
import java.util.Arrays;
import java.util.Scanner;
public class studentMethods
{
private double totalScore;
private int count;
[Code] ....
Creating a class. Specification are given as:
Create a class called Employee that includes three pieces of information as instance variables:
-Employee ID (string type)
-first name (string type) (default value 'John')
-last name (string type) (default value 'Smith') and
-monthly salary (type double).
-No argument constructor that initializes the three instance variables. The employee id should be generated using the following process:
The employee id should be a combination of first initial, last initial and a number starting from 10001 for the first employee and increasing by one for each employee. e.g. if John Smith is the first employee then its id will be JS10001 and if George Brown is the second employee then its id will be GB10002
-Provide get and set methods for each instance variable. The set method for monthly salary should ensure that its value remains positive - if an attempt is made to assign a negative value, leave the original value.
I am working on a game engine with java. I have come to the final stages of the development of this engine now and need a small hand. For this i am using java's built in libary for graphics. and am strugling to create a nice looking GUi with it, What i need:
The class extends the canvas class and adds it to the jframe, i have set the window up as standard and added a menubar, and net the canvas, what I want to do.
For those of you that have used application such as tiled (shown here [URL] .....) what i am wanting to do is create a gui around the canvas similar to this where the parts on the right are resizable up and down and in and out. i was wondering how i would go about incorporating this.
I'm using "standard-kepler-SR2-win32-x86_64" and have installed "jdk-8u5-windows-x64".
But eventhough I can't override a methode like that "@override", it still says me:"annotations are only available, if source lever is 1.5 or greater".
Fine, therefore I installad "jdk-8u5-windows-x64", its the higest one on that oracle side, what else is needed?
I have come across some code where it attempts to save an entity to a database, but before it does it validates that the name of the entity is unique. If it is not unique it throws a runtime exception. This results in the ugly default exception web page being displayed. Is there any way to propagate this back to the JSF page where the user enters and clicks the form button to save the entity? The page already handles some error cases such as "field required" using the h:inputText's 'required' attribute. Need something more for name validation.
View Replies View RelatedI know that below code would put a lock on current instance of DemoClass, What I am not sure of is the role of lock on Object Class in second example. How does below works - Is it putting a lock on Object Class? If yes how will putting a lock on Object? I mean, locking DemoClass ensure no two threads access it concurrently, how does this apply to Object class?
private final Object lock = new Object();
synchronized (lock)
public class DemoClass
{
public void demoMethod(){
synchronized (this)
[code]....
We are working with LinkedBinarySearchTrees. One of specs on my assignment is to "Using a level-order traversal, create a 2-D display of your trees, using the forward and back slashes as the branch lines. The tree nodes should be spaced proportionally to show the structure of the tree neatly."
View Replies View RelatedI need to do a simulation on the assembly code level by writing a mini-compiler for each ISA, i.e., 4, 3, 2-Address Architecture, Accumulator Architecture, Stack Architecture, and Load-Store Architecture.The input to the simulator is a segment of C program:The basic sample segments of C code are:
1. A = (B + C) * D - E;
2. F = (G + H) - (I + J);
3. G = H + A[I];
4. If (I == J) F = G + H;
Else F = G - H;
5. Loop: G = G + A[I];
I = I + J;
If (I != H) Goto Loop;
6. If (G < H) Goto Less;
7. While (save[I] == K)
I = I + J;