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);
}
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) ?
I want to know is there any way we can call parent class method using child class object without using super keyword in class B in the following program like we can do in c++ by using scoop resolution operator
class A{ public void hello(){ System.out.println("hello"); } } class B extends A{ public void hello(){ //super.hello(); System.out.println("hello1");
I have an admin class that needs to access a method of another class and I'm unsure how to do it.
One of the methods in the admin class (DancerAdmin) accesses a .txt file with information in and each line is to be extracted and is to be created as an object of the Dancer class. The information in each line is to then be used to set the variables in the Dancer class.
To set the values the Dancer class has setter methods which I need to access each time a new object is created while cycling through the .txt file. I'm struggling to access these methods from the DancerAdmin class when I run the relevant method.
The snippet of code I have from the method in DancerAdmin is
while (bufferedScanner.hasNextLine()) { currentLine = bufferedScanner.nextLine(); lineScanner = new Scanner(currentLine); lineScanner.useDelimiter(","); dancer.add(new Dancer()); Dancer.setName(lineScanner.next()); mh_sh_highlight_all('java');
I get an error saying non static method setName cannot be referenced from a static content?
A 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.
Why static member are allowed to be accessed with class-name and a null reference?
Here's the given code.
class Employee{ public static Integer companyId = 1001; // this could be private. public static Integer getCompanyId(){ return Employee.companyId; } //a setter method will be here if the companyId will be private. } public class TestStatic{ public static void main(String[] args){ Employee emp =null; emp.companyId = 11111; System.out.println(emp.getCompanyId()); } }
In this code the static members of a class are accessible by the null reference of that class.
These can also be access by the class (Employee.companyId or Employee.getCompanyId()).
What is the difference here in both. why a null reference can access these static members.
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
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
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?
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
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();
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.
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.
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); } }
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 ..
What I want to do is this, this is my first class:
public class Footballer { int goals; String surname= ""; String team=""; private static int counter=0; private int dres; }
(this is just the header of the class... And this is my second class, which contains an ArrayList of the first class:
public class FootballTeam{ String teamname=""; String league=""; ArrayList<Footballer> f; }
And this is my third class which contains an ArrayList of the second class:
public class FootballLeague{ String leaguename=""; ArrayList<FootballTeam> ft; }
What I want to do is, know how many of footballers are there in the league? Meaning how many of "f"s are in the "ft"... I remember from C++ it was easy, you just did it something like this: ft.f[i]; (where i is a position), then you'd go through each of them, if you wanted to do something with them, or just ask for it's length, if you needed to know how much footballers are there.
I'm trying this method to get the size of the array in the 2nd class, from the 3rd class (containing an ArrayList of classes of 2nd class, but no luck:
int counter=0; for(int i=0;i<this.ft.size();i++) { counter+=this.ft[i].f.size(); }
I'm getting this: Array required, but ArrayList<FootballTeam> found ---
What I want to do is this, this is my first class:
Java Code:
public class Footballer { int goals; String surname= ""; String team=""; private static int counter=0; private int dres; } mh_sh_highlight_all('java');
(this is just the header of the class, just how it looks)...
And this is my second class, which contains an ArrayList of the first class:
Java Code:
public class FootballTeam{ String teamname=""; String league=""; ArrayList<Footballer> f; } mh_sh_highlight_all('java'); And this is my third class which contains an ArrayList of the second clas: Java Code: public class FootballLeague{ String leaguename=""; ArrayList<FootballTeam> ft; } mh_sh_highlight_all('java');
What I want to do is, know how many of footballers are there in the league? Meaning how many of "f"s are in the "ft"... I remember from C++ it was easy, you just did it something like this: ft.f[i]; (where i is a position), then you'd go through each of them, if you wanted to do something with them, or just ask for it's length, if you needed to know how much footballers are there.
