Why I can create an Instance of a class that contains non static variables within the static main method ?
This program runs fine
import java.util.*;
public class Test{
public int j;
public static void main(String[] args) {
Test test1=new Test();
System.out.println(test1.j);
[Code] .....
From what i understand static methods should be called without creating an instance of the same class . If so why would they return an instance of the same class like in the following : public static Location locateLargest(double[][] a) , the Location class being the same class where the method is defined . I don't understand this , does it mean that every field and every method in the class must be static ? Meaning that you cannot have instances of the class because everything is static . Or it's just a mistake and the class Location cannot have a static method: public static Location locateLargest(double[][] a) ?
View Replies View RelatedAlright, I have two classes, this one
public class Player {
private String player;
public String getPlayer() {
return player;
}
private int strength;
private int defense;
[Code] .....
However, it says that under Player.getPlayer() that it 'Cannot make a static reference to the non-static method'.
This is my code inside the method:
@Post
public static String getDetails(Representation entity) throws Exception {
String customerId = getQuery().getValues("cus_id");
}
I use this code in Restlet Representation. I try to get the value from the Request API. But I am facing the problem as "Cannot make a static reference to the non-static method getQuery() from the type Resource".
I can't figure out what this error message "Cannot make a static reference to the non-static method getEndUserCharge(long, long, long, long) from the type UpdateUserWS" actually means.
The error is coming from:
public void updateDetailsPackage() {
some unrelated code
long zero=0;
double endUserCharge=0;
endUserCharge = UpdateUserWS.getEndUserCharge(long zero, long zero, long zero, long zero); <-------- error is here
[Code] ....
I'm working on a banking program that is supposed to use 3 classes (Account-base class, CheckingAccount, and SavingsAccount) and several methods to display the banking information (ID, balance after a withdrawal and deposit, and the annual interest rate). This should be a pretty simple program, but I'm getting hung up on one portion of it. I'm getting some compiler errors, all of which deal with non-static variables being called from a static context (I'll also post these errors following the code). Up until the middle of last week, we just declared everything as static, but that's changed and I'm having trouble figuring out when to and when not to use static when declaring my methods, hence the compiler errors.
import java.util.Date;
public class Account {
private int id = 0;
private double balance = 0;
private double annualInterestRate = 0;
private Date dateCreated = new Date();
[Code] ....
Here are the compiler errors I am receiving:
Compilation completed. The following files were not compiled:
6 errors found:
File: C:UsersHiTechRedneckDesktopSummer II 2014Computer Programming PrincipleProgram 5CheckingAccount.java [line: 7]
Error: non-static method getId() cannot be referenced from a static context
[Code] .....
I had a TestColor class which contained methods to change hue, saturation, brightness, red, green, blue of TestColor's instances but also had static methods which take in an additional parameter for an instance of TestColor and returns the affected instance of TestColor. Now instead of having one method for every possible color effect to be applied to an image, how can I have one method that takes in an Image parameter, a static or non-static method reference from TestColor parameter and lastly an intensnity value parameter. This is so that I can make an affectedImage object instance inside the method and a Graphics2D object for drawing to each pixel of the new image, now I have one for loop and one nested for loop for the x and y pixels of width and height of the old image and inside the nested for loop I'd create a TestColor by calling getRGB on the image's pixel. Then I would apply the static or non-static method reference somehow to change the color with the intensnity value and after applying it draw to the new Image with Graphics2D. How to would I parametize a method reference and be able to use it in such way?
View Replies View RelatedOne class having two method one as static n another as non-static, 2 threads are there t1 is accessing the static method and t2 the non-static method is it possible n both are sharing the same object.
I now we have two kinds of lock one is object level lock and another is class level lock
I am trying to compile the following code where the entry point is Main.java but i am getting the following error "Error non-static method add(int[]) cannot be referenced from a static context in Java " ....
If i add the keyword static in add method of A.java it works properly......
Class Main.java code
package com.company;
public class Main {
public int [] a= new int[]{1,2,3};
public static void main(String[] args) {
Main n= new Main();
[Code]...
Both the classes are in same package
This is a someway special question, because I am using jmonkeyEngine.
But the topic is simple:
I have 2 classes:
public class Spielbrett extends SimpleApplication {
public static void main(String[] args) {
Spielbrett app = new Spielbrett();
app.start();
}
@Override
public void simpleInitApp() {
[Code]...
as the main class and a second class for the chips:
public class Spielstein {
public Spatial stone;
public int player;
public int team;
private AssetManager assetManager = Spielstein.getAM(); //THIS IS THE PROBLEM
public Spielstein(int t_player, int t_team){
[Code]...
My problem is: I can't access getAM() from the first in the second class. If you know why I would be glad for an answer.
Which is more efficient static block or static method ?
View Replies View RelatedI’m trying to understand how to decide when to make a nested class static or non-static. These are my assumptions.
1) Make a nested class static if each instance of its enclosing class may have one or more instances of its nested class, for example, a HashMap has a static HashMap.Entry nested class because each HashMap instance may have one or more HashMap.Entry instances
2) Make a nested class non-static if each instance of its enclosing class must have only one instance of its nested class, for example, an AbstractButton has a non-static AbstractButton.Handler nested class because each AbstractButton instance must have only one AbstractButton.Handler instance.
I wrote a code to use static class. But, when I call the class in a outer class but, it gives an error. Is it mandatory to have a static class should have static variables when we declaring them??
public class StaticClassMain {
static class Sub{
String str="Example 1";
}
public static void main(String[] args) {
System.out.println(Sub.str);
}
}
I am getting an error trying to access a static method of another class...theyre both in the same package, I've tried importing the class.
I've tried to do A b=new A()
and then
b.evaluate();
Everything that I try I get the following error:
Exception in thread "main" java.lang.NoClassDefFoundError: B$A
Caused by: java.lang.ClassNotFoundException: B$A
at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
Code :
public class A{
public static String evaluate(String op) {
}
}
public class B{
String output=A.evaluate(input);
}
is it necessary that inner classes inside a static method be static . If yes Why?
View Replies View RelatedA common solution to this problem is to write a utility class whose responsibility is to log information. This class can have a flag that will allow you to turn the logging on and off. In addition you should be able to tell the class how much detail you want in the output. Ultimately, this class will give you the ability to control when information is logged, what information is logged, how often information is logged, and even where the information is logged. And you would be able to control all of this without changing a single line of code!
This type of utility class is commonly written using static methods and is referred to as a static class. In order to use the features of a utility class, the application can access the methods directly by referring the class name, eliminating the need to create an instance of the class in order to execute the methods.
What happens to a static variable that is defined within a method of a class ?
View Replies View RelatedTake this:
class test
{
static int i=j;
static int j=10;
.....
this will give illegal forward reference ....
but this will compile successfully ..
class test
{
static int i=test1();
static test1()
{
return 20;
}
}
.....
plz assume we have main method in both cases ..
java would be loading all static members first and would be assigning default values .. and then will be running all the initializers from to bottom ..Why second case is a compile success and not first .. as in second also test1 method is declared after its usage ..
class Test
{
static Test ref;
String[] arguments;
public void func(String[] args)
{
ref.arguments = args;
[code]...
This code run perfectly.But the static method is acessing a non static method which was supposed to be not possible.
We know that a non static method can not be directly refrenced from static method but in the example given below there is no such error.Why?
class A
{
private void display()
{
System.out.println("In A");
}
public static void invoke (A x)
{
x.display();
[code]....
In above case a non static method display() is being invoked from static method invoke ()but it is not giving error.why?
I'm doing in this small piece of code -
JavaApplication3.java
package javaapplication3;
public class JavaApplication3 {
public class robot {
int xlocation;
int ylocation;
String name;
static int ccount = 0;
[Code] .....
When I'm trying to compile it with netbeans i get these errors and i just can't figure why is that!
C:UsersuserDocumentsNetBeansProjectsJavaApplication3srcjavaapplication3JavaApplication3.java:16: error: Illegal static declaration in inner class JavaApplication3.robot
static int ccount = 0;
modifier 'static' is only allowed in constant variable declarations
C:UsersuserDocumentsNetBeansProjectsJavaApplication3srcjavaapplication3JavaApplication3.java:30: error: non-static variable this cannot be referenced from a static context
robot firstrobot = new robot(34,51,"yossi");
Can we use static variables or static objects in servlets ?? I want to restrict same user to enter into the application from different system when the user is already working, he needs to get a message saying "User is already in use ".
I have created static SET object in LoginServlet and inside doget() I checked if SET contains user ,if yes display him above message otherwise add the user in SET object and forward it to next page . Later while logging out user is removed from SET .
Can I follow any other approach other than using static object SET in servlets??
why using the get method(c.get(c.HOUR_OF_DAY)); gives me the correct hour(currently 19) but directly accesing c.HOUR_OF_DAY returns 11 ? It shows In the documentation that HOUR_OF_DAY is public.
import java.util.*;
public class calendar2 {
public static void main(String[] args) {
new calendar2().timer();
}
private void timer() {
Calendar c=Calendar.getInstance();
//c.clear();
System.out.println(c.get(c.HOUR_OF_DAY));
System.out.println(c.HOUR_OF_DAY);
}
}
Say I have a class called ClassA which I want to hold my data. Now inside ClassA want to hold instances of a class lets call ClassB. So far we are here.
import blah.B
public class A {
private B myB;
(Getters setters etc)
public String getBString() {
B.getString();
}
}
However I want to have multiple extensions of ClassB which have UNIQUE static variables.
public class B-1 extends B {
private static String mString;
private static int mInt;
}
The problem I have run into is I can't have subclasses with their own static variables. I need the A class to hold any type of B class. How can I manage this?meant
public String getBString{
return B.getString();
}
I'm new to Java and I'm trying to create a spanning tree in the desired order with 4 nodes (0,1,2,3). I've got the following code:
import java.util.ArrayList;
public class A {
public static boolean any(ArrayList<Integer> input) //To check for if any element in the ArrayList == 1
{
boolean answer = false;
for(int i=0;i<input.size();i++) {
if(input.get(i)==1)
[Code] ....
What happens is that the input parameter adj and hence the original adjmat inside main gets changed everytime I enter the method "connected", and I don't want this to happen. I understand that this is due to the main method being static and hence adjmat becomes static as well, but how do I change the code such that adjmat only gets modified after coming out of the connected function, and not while inside it?
Are the static variables in servlet thread-safe?
View Replies View Related