public static final String NAME="JAVATAR";
"final" makes sure the constant has the same value and prevents it from being changed. So why add "static" to make it a constant. I figured the reason a few weeks back but don't remember it now.
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] ....
Alright, 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'.
I am writing the following program in Java SE 7. It throwing "Cannot make a static reference to the non-static type String" . However if I write parameterised String inside main method as java.lang.String[] args, it compiles fine.
class MainClass<String> {
<T> MainClass(T t) {
System.out.println(t.getClass().getName());
}
public static void main(String[] args) {
System.out.println("asdasd");
new MainClass<>("");
}
}
I mean following programs compile fine in Java SE 7 :
class MainClass<String> {
<T> MainClass(T t) {
System.out.println(t.getClass().getName());
}
public static void main(java.lang.String[] args) {
System.out.println("asdasd");
new MainClass<>("");
}
}
Suppose I have a class child
public class child{
public static int age = 1;
}
And I am using class child static variable age in class school
public class school{
int var_age;
public school(){ //school constructor
var_age = child.age;
}
}
Value in age of child class could be any of these below depending on some logic:
public static int age = 1;
public static int age = 2;
How could i achieve this where should i apply that logic? Also it is mandatory for class school code to remain same.
How to make sure that a variable passed to a method isn't altered by the method? I know in C++ you can do something like
void aMethod(const Object &item) {
........
}
I know that you can stop a variable from being reinitialized in java by doing this
void aMethod(final Object item) {
.........
}
However, that won't stop it from calling a setter on the item or changing something in it. Is there some other keyword out there that can do this? I just found that java DOES recognize the const keyword but that it really is useless.
So, any practical way that const can be further approximated in java beyond using final?
"Because X is a compile time constant, the compiler will Y"... But what exactly is a compile time constant? And how can we determine whether something is treated as such?Obviously, a compile time constant is a constant value that is known at compile time... ... Literals are, by definition, compile time constants -- as they are constants, known at compile time.
But the definition of a compile time constant is a bit more complex. To start, let's examine section 15.28 of the Java language specification.A compile-time constant expression is an expression denoting a value of primitive type or a String that is composed using only the following:
Literals of primitive type and literals of type String Casts to primitive types and casts to type StringThe unary operators +, -, ~, and ! (but not ++ or --)The multiplicative operators *, /, and %The additive operators + and - The shift operators <<, >>, and >>>The relational operators <, <=, >, and >= (but not instanceof)The equality operators == and !=The bitwise and logical operators &, ^, and |The conditional-and operator && and the conditional-or operator ||The ternary conditional operator ? : Simple names that refer to final variables whose initializers are constant expressions Qualified names of the form TypeName . Identifier that refer to final variables whose initializers are constant expressions
This is the full definition of a compile time constant. And as you can see, it contains more than just literals. In fact, literals are merely the first bullet point on the list. Also, note that a compile time constant can apply to any literal that is of primative or String type.The next few bullet points are the operations that can be applied to a constant at compile time. This list is actually pretty long, as it is possible to apply most of the operations at compile time. It may actually be easier to remember what can't be apply at compile time -- pre and post increment and decrement, instanceof operator, or any method calls, are not on the list.
The last few bullets are the most interesting. It is possible to use a variable in the expression -- provided that the variable is a compile time constant variable. So... what is a constant variable? Going back to the JLS (section 4.12.4 to be exact)..4.12.4 final Variables.A variable can be declared final. A final variable may only be assigned to once. It is a compile time error if a final variable is assigned to unless it is definitely unassigned (§16) immediately prior to the assignment.
We call a variable, of primitive type or type String, that is final and initialized with a compile-time constant expression (§15.28) a constant variable. Whether a variable is a constant variable or not may have implications with respect to class initialization (§12.4.1), binary compatibility (§13.1, §13.4.9) and definite assignment (§16).The last part of the definition is the relevant part (I still find it amazing that this is that well hidden in the specification). To be a variable that is a compile time constant, the variable needs to be...declared as finalhave a primative or String typeinitialized (on the same line as the declaration)assigned to a compile time constant expression.
I'm new to Java and have been stuck on how to use a final declaration statement once it's made. Below is a class I'm creating with the intention of calling it under a main method. I don't understand if I'm supposed to do anything else, like do some sort of get/set, or if the final static line is all I need. And, I don't know how I call it to the main method once I do.
public class Shirt//class name.
{
int collarSize;//data field.
int sleeveLength;//data field.
public final static String MATERIAL = "cotton";//final data field for material.
[Code] ....
I am trying to write a java program that prints out the number that is the mathematical constant e. As you input a number, the larger it gets , the closer it comes to 2.71828 . Here is my code:
//taylor series that prints out e^1=1+1/1!+1/2!+1/3!+.....
import java.util.Scanner;
public class taylor_1
{
public static void main(String args[]) {
Scanner input=new Scanner(System.in);
int factorial =1;
[Code] .....
Here is the output of my code:
enter n
9
Taylor series is 9.0
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 RelatedWhy 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] .....
I am trying to call an actionListener which is shown below in my PSVM :
class testMenuItemListener implements ActionListener {
public void actionPerformed(ActionEvent arg0) {
getContentPane().removeAll();
createPanel();
getContentPane().add(panel1); //Adding to content pane, not to Frame
repaint();
printAll(getGraphics()); //Extort print all content
[Code] .....
I get the following error :
Frame.java:409: error: non-static variable this cannot be referenced from a static context
menuItem1.addActionListener(new testMenuItemListener());
I am trying to add a field (called special) to a hibernate table. I am copying existing code (related to the NAME field) so I don't have to figure this out from scratch. I am getting the error
"[ERROR] C:VOXvoxware-1.1.13voxwarevoxware-implsrcmainjavacomvoxwareimplflowVoxFlowConfiguration.java:[213,38] error: non-static variable special cannot be referenced from a static context".
Line 213 is in public void mergeFrom, the actual line is "special = VoxFlowConfiguration.special;" I don't understand why Java thinks special is a "non-static" variable but it doesn't have a problem with the other variables (such as name, orderShow)
package com.voxware.impl.flow;
import com.voxware.asset.LiabilityType;
import com.voxware.flow.FlowConfiguration;
import com.voxware.flow.OrderFlow;
import com.voxware.flow.Step;
import com.voxware.i18n.LanguageCodes;
import com.voxware.impl.i18n.UTF8Control;
import com.voxware.impl.persistence.BaseEntity;
import com.voxware.impl.portal.VoxPortal;
[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 am trying to call an actionListener which is shown below in my PSVM :
class testMenuItemListener implements ActionListener
{
public void actionPerformed(ActionEvent arg0) {
getContentPane().removeAll();
createPanel();
getContentPane().add(panel1); //Adding to content pane, not to Frame
repaint();
[Code] .....
I get the following error :
Frame.java:409: error: non-static variable this cannot be referenced from a static context
menuItem1.addActionListener(new testMenuItemListener());
i am trying to make something, and i want to request input from user and it shoud look like this
1. xxx -> press 1 to choose this
2. xxx -> press 2 to choose this
So if they enter 3 or string or whatever i want to restart method and show again
1. xxx -> press 1 to choose this
2. xxx -> press 2 to choose this
So here is method that i am trying to restart
public static void askUser(){
System.out.println("xxx");
System.out.println("1. xxx");
System.out.println("2. xxx");
System.out.println("3. xxx");
[code]....
If i try to make it public void than it say can't call non-static methods inside static(main).if i try to put it into new class and then call it after i fail input it goes into infinite loop.
The error said : Non Static Variable TAShaReport Cannot referenced from a static context
I just want to put the output in the TextArea
Here is the code :
public static String DeduplicateFiles(String myFolderLocation) {
try {
HashSet<String> newset = new HashSet<>();
File folder = new File(myFolderLocation); //Directory where the files are located
File[] listOfFiles = folder.listFiles();
[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 RelatedThis 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.
This is the overall code:
public class Bank {
/**
* Customer class.
*/
public class Customer {
private String firstName, lastName, street, city, state, zip;
[Code] .....
The error occurs when I attempt to create the new object Account within the main arguments here:
Account munozAccount = new Account(250, "Maria", "Munoz", "110 Glades Road", "Mytown", "FL", "33445");
I'm not sure how to access the generator method, so i'm completely stumped.
One of my friend asked me that which will load first static variable or static block ? My answer was to static variable.. So he gave me two program and said to differentiate between them
1st program
public class Test {
public static void main(String args[])
{
System.out.println(Test.x);
}
static {
System.out.println(Test.x);
[Code] ....
Output of this :
90
90
I tried to decompile the byte code and found it's same for both the above equation. How to differentiate between them. I am confused when the static variable will initialised.
One 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
package Experimentation;
import javax.swing.*;
import java.awt.event.*;
public class SimpleGUI1B implements ActionListener {
JButton button;
public static void main(String[] args) {
SimpleGUI1B gui = new SimpleGUI1B();
gui.go();
[code]...
This is a program from Head First Java! since main is static it shouldn't be able to call non-static methods because statics do not use any instance variable values but in the above program we're call a non-static method go() how is it possible?
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
I’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.