How To Call Non Static Methods From Other Classes
Apr 16, 2015
how come you can call non static methods from other classes(objects when they are created from main) but not static methods in the same class as the main method??
example I cannot call the method maximum from the main method aslong as its not static BUT i can call other objects non static methods from main??
class test{
public static void main(String [] args){
Scanner input = new Scanner(System.in); //create new Scanner object
//for input
int number1;
int number2;
[Code]...
View Replies
ADVERTISEMENT
Aug 19, 2014
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.
View Replies
View Related
Oct 21, 2014
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?
View Replies
View Related
Apr 18, 2014
How do you call classes within other classes? Or can you only call classes through the main?
View Replies
View Related
Jun 9, 2014
How do i call the method without using inner classes in this example:
jt = new JTable (model) {
public boolean isCellEditable (int row, int col) {
if (col == 5) {
return false;
[Code] ....
View Replies
View Related
Aug 15, 2014
The requirements are as follows:Design and implement the class Day that implements the day of the week in a program. The class Day should store the day, such as Sun for Sunday. The program should be able to perform the following operations on an object of type Day:
A. Set the day.
B. Print the day.
C. Return the day.
D. Return the next day.
E. Return the previous day.
F. Calculate and return the day by adding certain days to the current day. For example, if the current day is Monday and we add four days, the day to be returned is Friday. Similarly, if today is Tuesday and we add 13 days, the day to be returned is Monday.
G. Add the appropriate constructors.
H. Write the definitions of the methods to implement the operations for the class Day, as defined in A through G.
I. Write a program to test various operations on the class Day.Should I break down my day.java into several separate classes, one for each of the sections (previous, next, etc)?
import java.util.*;
public class MyDay
{
static Scanner readinput = new Scanner(System.in);
String day;
public MyDay(String day)
{
day = "Sunday";
[code]....
Ideally I would like to create a Gui that would have someone type in the day, and then press a button to return the next day, prior day, or have a text input to test for adding X number of days.
View Replies
View Related
Oct 25, 2014
I am reading about interface and i see that classes are allowed inside interfaces which are implicitly static. Here is sample of code i created and i am able to access the static method and fields as well. Here is the code snippet.
public class TestInnerClass {
public static void main(String[] args){
Test.NestedClass.printMe();
}
}
interface Test{
static class NestedClass{
static int x = 100 ;
public static void printMe(){
System.out.println(x);
}
}
}
My question is what is the use of such static classes inside interface? If i don't have access to Foo, i can't ever invoke NestedClass. Whats the design usage?
View Replies
View Related
Jun 2, 2014
If I had this code:
<h:dataTable value="#{customer.customerList}" var="c"
styleClass="order-table"
headerClass="order-table-header"
rowClasses="order-table-odd-row,order-table-even-row"
>
And in the server getCustomerList() accessed to database, how many times getCustomerList() would be called from I request the xhtml page?. I have read this would be called several times because of JSF internals and It would be better to store it in a variable and access this variable.
1. Is this true this would be called several times? why?
2. If the previous statement was true, how to avoid it, I mean not call the method from a service?
View Replies
View Related
Apr 17, 2014
Life Cycle Call back methods(init(), destroy(),...) are not transactional by default and expecting this in coming EJB releases (EJB 3.x / EJB 4.x). I was expecting next EJB release along with Java 8, but it stays at 3.2
View Replies
View Related
Jun 16, 2010
Why can't we have static methods in an interface?
View Replies
View Related
Sep 11, 2014
Question:_public class TaxComputer {
private static double basicRate = 4.0;
private static double luxuryRate = 10.0;
1. Create a class that will bundle together several static methods for tax computations. This class should not have a constructor. Its attributes are
• basicRate—the basic tax rate as a static double variable that starts at 4 percent - a private static method
• luxuryRate—the luxury tax rate as a static double variable that starts at 10 percent - a private static method
Its methods are
• computeCostBasic(price) —a static method that returns the given price plus the basic tax, rounded to the nearest penny.
• computeCostLuxury(price) —a static method that returns the given price plus the luxury tax, rounded to the nearest penny.
• changeBasicRateTo(newRate) —a static method that changes the basic tax rate.
• changeLuxuryRateTo(newRate) —a static method that changes the luxury tax rate.
• roundToNearestPenny(price)—a private static method that returns the given price rounded to the nearest penny. For example, if the price is 12.567, the method will return 12.57.
My code:
public class TejvirThindCh6Ex1 {
/**
* @param args the command line arguments
*/
//Atributes
private static double basicRate = 4.0;
private static double luxuryRate = 10.0;
public static double computercostbasic(double price)
[Code] .....
View Replies
View Related
Apr 14, 2014
I need to create a Dog class that represents a dog. Then, there are 2 different methods that in the end will each represent one dog each. Each printout will show the Name, Breed, Age, and Age in Human Years. Right now I'm having trouble trying to move methods in between each class. Here's the first class.
import java.util.Scanner;
public class Dog { //no main method
static Scanner input = new Scanner(System.in);
//writeObject method
public static void writeObject(String name, String breed, int age) {
System.out.println("Enter the dog's name, breed, and age: ");
[Code] ....
View Replies
View Related
Mar 25, 2015
I am trying to make a 2d graphical animation using the java swing classes in order to make a frame. I had a basic version working when all of the code was under the main method, but when I moved some into another method it broke it. With y understanding of java my code should work as I create a variable of the method containing the code and then assign the size and exit button. However this causes many problems such as my BeaconFrame method informing me that it is unused when I have used it. Here is my code:
import javax.swing.*;
import java.awt.*;
public class BelishaBeacon {
public void BeaconFrame() {
JFrame frame = new JFrame();
JPanel panel1 = new JPanel();
[code]....
View Replies
View Related
Jun 17, 2014
Declaring the method as static precludes one from using any sort of object oriented programming, thus the method cannot access instance fields of the object if it needs to.
I created two short classes to sort of find out what this meant, but I feel I do not understand it well enough.
Test class (main):
package votek;
public class Test {
public static void main(String[] args) {
SomeMethod();
}
public static void SomeMethod() {
Character character = new Character();
character.totalLevel = 50;
System.out.println(character.totalLevel);
}
}
Character class:
package votek;
public class Character {
private int level = 0;
public Character() {
level = 50;
}
}
OR
Does it mean that making a static method in the class with private instances will prevent the method from using the private instances?
View Replies
View Related
Feb 4, 2015
I have a very standard Lab assignment. It's probably been seen a lot. I wrote the first part not realizing I had to write a second class to do use the methods. I'm not sure how to change my program to call methods from my second class instead of doing all my calculations with user input in my first class.
Here's the first class' code:
package tickets;
//Imports classes used for "Ticket" application.
import java.util.*;
import java.text.DecimalFormat;
public class Tickets {
[Code] ......
The code is obviously incomplete. I have not tried to compile, nor would I expect it to compile right. I'm not sure how to move my calculations from the first class shown above into my second class and use them as methods.
View Replies
View Related
Sep 20, 2014
Basically I want to make a class called library, but I don't want to make an interface because I actually want to define the methods. I think I can only use abstract classes but not really sure how to use those. But I still have a problem, I want to create a Map that classes implementing Library class have to have in their code, and the Map will be a HashMap with <String, ParentClassHere>, so basically let's say I make a class called Car, implemeing Library to the Car class would create a Map library = new HashMap<String, Car>. Can I do something like this? And also include methods to get values and set values to the library Map?
View Replies
View Related
Aug 6, 2014
I have a question about a method I have. In my game, I had a move method to move my player left and right, and originally this method was huge, as it also took care checking collisions and a few other things. I broke it up a bit and put the collisions in their own methods and call them from again another method... Here is an extract which I hope illustrates my point:
private static final double MOVE_SPEED = 0.2;
private static final double MAX_MOVE_SPEED = 3.5;
private static final double STOP_SPEED = 0.18;
private double xPos;
private double yPos;
[Code] .....
Something I thought might be a good idea is to check the direction collision when im doing the calculations for that direction:
if(moveLeft) {
dx -= MOVE_SPEED;
(dx < -MAX_MOVE_SPEED) {
dx = -MAX_MOVE_SPEED;
}
checkLeft();
}
But then I would also need to check it when I'm slowing down the left movement:
if(dx < 0.0) {
dx += STOP_SPEED;
if(dx > 0.0) {
dx = 0.0;
}
checkLeft();
}
Then I thought instead i can check it after both of these steps:
if(moveLeft || dx < 0.0) {
checkLeft();
}
I guess my question is quite general: How much is acceptable to break up a method? How many chains of method calls is acceptable? Is it ok to call the same method from different nearby places?
View Replies
View Related
Feb 19, 2011
I thought static methods could never use instance variables, because they wouldn't know which instance to look at.
From Head First Java, p. 284: "A static method is not associated with a particular instance - only the class - so it cannot access any instance variable values of its class. It wouldn't know which instance's values to use."
Now I was answering some mock exam questions from Cameron McKenzie's SCJA book, and I don't understand one of the options. On page 205, the last question has an option that says: "Instance variables ... are not visible in static methods, unless passed in as arguments." This option is supposed to be correct. Now... how does that work?
View Replies
View Related
Oct 7, 2014
This is titled "Creating static methods that accepts arguments and returns a value". I think that I understood everything about this except for the very bottom part of the code. I wasn't really sure where to put it. From the errors that I am seeing, I know which line is giving the errors but I'm not sure what is wrong with it.
import java.util.Scanner;
public class ParadiseInfo2{
public static void main(String[] args){
double price;
double discount;
[Code] ....
Errors:G:ParadiseInfo2.java:29: error: illegal start of expression
public static double computeDiscountInfo(double pr, double dscnt)
^
G:ParadiseInfo2.java:29: error: illegal start of expression
public static double computeDiscountInfo(double pr, double dscnt)
[Code] ....
6 errors
Tool completed with exit code 1
View Replies
View Related
Jun 4, 2014
I have a javafx class that has buttons and textfields. Here is the code for a button, and i want the button to make a new object but im having trouble setting the constructor
Label label = new Label("Type");
GridPane.setHalignment(label, HPos.RIGHT);
TextField textField = new TextField();
Label label2 = new Label("First Name");
GridPane.setHalignment(label2, HPos.RIGHT);
TextField textField2 = new TextField();
[Code] ....
after i create the object i will insert the object in an arraylist of person objects
View Replies
View Related
Apr 1, 2015
Consider the two simple Java classes below:
Java Code:
class Computer {
Computer() {
System.out.println("Constructor of Computer class.");
}
void On() {
System.out.println("PC turning on...");
}
void working() {
[Code] ....
After the program run, how do I trace (1) which object call which method (2) and how many times?
View Replies
View Related
Dec 19, 2014
For reference I am programming Java in BlueJ. I am fairly new to the language and I am having trouble with sorting.
I am trying to call / test all of the 5 sorting methods (at the same time) in the main class. To be specific, the sorted list has to technically outputted 5 times.
I figured out how to call / test Quicksort:
Sorting.quickSort(friends, 0, friends.length-1);
But the others are not working correctly. Specifically these:
Sorting.mergeSort(friends, 0, friends.length-1);
Sorting.PbubbleSort(friends, 0, friends.length-1);
Sorting.PinsertionSort(friends, 0, friends.length-1);
Sorting.selectionSort(friends, 0, friends.length-1);
For reference, this is the output when it is not sorted:
Smith, John 610-555-7384
Barnes, Sarah215-555-3827
Riley, Mark 733-555-2969
Getz, Laura 663-555-3984
Smith, Larry464-555-3489
Phelps, Frank322-555-2284
Grant, Marsha243-555-2837
This is the output when it is sorted:
Barnes, Sarah215-555-3827
Getz, Laura 663-555-3984
Grant, Marsha243-555-2837
Phelps, Frank322-555-2284
Riley, Mark 733-555-2969
Smith, John 610-555-7384
Smith, Larry464-555-3489
This is the class Sorting, which I should note is all correct:
public class Sorting{
/**
* Swaps to elements in an array. Used by various sorting algorithms.
*
* @param data the array in which the elements are swapped
* @param index1 the index of the first element to be swapped
* @param index2 the index of the second element to be swapped
*/
private static <T extends Comparable<? super T>> void swap(T[] data,
int index1, int index2){
T temp = data[index1];
data[index1] = data[index2];
[Code]...
This is the Main class in which I am supposed to call the sorting methods, SortPhoneList:
public class SortPhoneList{
/**
* Creates an array of Contact objects, sorts them, then prints
* them.
*/
public static void main (String[] args){
Contact[] friends = new Contact[7];
friends[0] = new Contact ("John", "Smith", "610-555-7384");
friends[1] = new Contact ("Sarah", "Barnes", "215-555-3827");
[Code]...
View Replies
View Related
Jan 8, 2014
I am writing a game in Java for Android (although my question isn't Android or Game Dev specific).
I have a SceneManager class and a Scene interface and then various other classes that implement the Scene interface (Code at the end of this post).
Basically, in my MainGame class (which also implements the Scene Interface for Touch Event capturing purposes) I hold the bulk of my game code. Methods in this class are then called from my Level classes. (most of these are needed in all levels so it makes sense to hold them here and call them from the levels to eliminate unnecessary code duplication)
So, I have Level1, Level2......... Level20 classes which all implement Scene.
Now, the problem comes because in only 2 of my Levels something can happen (that can't in the other 18) and I need to run a response method in these 2 levels (the method isn't exactly the same, the response to this event happening is different for both levels).
To run common methods from my classes, I use my Scene Manager like this:
SceneManager.getInstance().getCurrentScene().updateLogic();
SceneManager.getInstance().getCurrentScene().render();
(The above is from my gameloop) - So it will run the updateLogic(); and render(); methods from whichever is the current scene (Level).
Scene is changed like so:
SceneManager.getInstance().setCurrentScene(LevelX);
This works great as all Level's have an updateLogic(); and render(); method.
So from my mainGame class, I am doing something like : (pseudo code)
public void checkIfSomethingHappened(){
if (something happens){
if (currentLevel==5){
Level5.response();}
[Code]....
The above would be called from my 2 level classes. So something like:
MainGame.checkIfSomethingHappened(); //Called in addition to the normal methods that make up that level
I don't really want to have this (second) 'if' statement here in the middle of my performance critical game loop.
What I'm after is something like this:
if (something happens){
SceneManager.getInstance().getCurrentScene().response();
}
However, this would require me to put stubs in the other 18 classes.
I'm thinking there must be a way to do this as the SceneManager already knows the current scene so it seems a waste checking it again via an if (or switch) statement. What is the best way to do this without having to put stubs into classes that don't require this method?
View Replies
View Related
Feb 7, 2015
I am trying to pass an object of type Product p to my editProduct method, however trying to call p.getName(); doesn't work and throws a NullPointerException. The same kind of thing works for my displayRecord method (in a different class) and I can call .getName() on Product p, also passed as an argument to that method. Below is my editProduct class. The NullPointerExcepion is being thrown at line 61 (i.e., nameField.setText(p.getName());).
I don't know if I explained right, so here's a line thing of how the classes relate:
Search >>>(field.getText())>>> displayRecord(Product p) >>>editProduct(p)>>> EditProduct
And as a side note: adding the line p = new Product(); fixes it and successfully runs the class (including the Save and Quit parts) but obviously I want it to specifically refer to the Product I pass to the method.
Java Code:
import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.FocusEvent;
import java.awt.event.FocusListener;
import java.util.ArrayList;
import javax.swing.BorderFactory;
[Code] ....
I'm asking a question because I don't understand how Product p could possibly be null, because the argument is passed through my DisplayRecord class, which also takes a Product p argument and works. In that class, I have declared Product prod = p; and prod is what I am passing to editProduct.
View Replies
View Related
Apr 14, 2015
I create 2 files:
CircleCalculationMethod.javaMain.java
In Main.java, How can i call method in CircleCalculationMethod.java ?
Should I put everything in same folder ??Should i do something like "import CircleCalculationMethod.java"Should i do something like create a package ...
I use Eclipse software
View Replies
View Related
Mar 26, 2015
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".
View Replies
View Related
