I have a test that covers Objects & Classes, Importing Classes and Polymorphism. One of the essay questions will be: Explain two ways to pass arguments to methods and give examples. I was reading the book and found Pass by Value and Pass by Reference. Is this the two ways to pass arguments?
I am looking to write a constructor (in a herited class) to initialize the name of a single piece and its orientation using values passed as parameters. If no value is given for guidance , it returns "none" , I do it in this way but i am not sure it is the right way:
I want to take command line arguments and pass them to a paint method. This is a test program that will just draw some equations. How can I get the input array clinputs[] to be used in public void paint( Graphics g) ?
import java.awt.*; import java.awt.event.*; import javax.swing.*; public class LinePlot extends JFrame { public LinePlot() { super( "Line Plot" ); setSize(800,600);
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?
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)
How do I pass the data within an initialized array from inside one method to another method of the same class? Will I need to return the array, assigning it to a temp array, which will then be passed as an argument to the other array? The idea is to create an array for an entire year, and be able to manipulate or edit data for a particular month using the other method.
public class Temperature { static Scanner input = new Scanner(System.in); static String [] monthArray = {"January", "February", "March", "April", "May", "June", "July", "August", "October", "November", "December"}; public static void main(String[] args) {
in my progrm there are three diff array of objects...namely garments..gadgets and home app...now one who buys from each of these sections will have to make a bill at last...when he choses to make the bill he will be shown the list of products he bought and their details (like price...brand...etc)...so i thought that while he orders each product(which is done in a previous method called purchase()...)....(each product is stored as an object in there diif arrays namely garments...gadgets ...appliances)....each of those object will be copied in a new array in a diif class...then that array print will give me the desired result...
is this approach correct...?and if its correct then how can i pull out a specific obj frm a stored array of object and then save it in a new array....?
I wish you could share some methods for securing access to webpages of websites you had had a hand on? I know of:
- asking for user credentials from an entry page and processing them inside a javabean to confirm they are equal to those kept in the system before granting further access. - masking servlets paths in web.xml - hiding client scripts in libraries that are kept on server
I have been assigned to write a program that has a user input random numbers then the program is to sort them in different ways. I have the coding for the different sorts but, I have an error saying that I am missing a return statement in the "Bubble" method. I am trying to return "arr[i]" in the "for loop" which gives me this error, and when I try to take the "return arr[i]" outside of the "for()" loop the error reads the it cannot locate variable "i".
import java.awt.* ; import java.awt.event.*; import javax.swing.*; public class SwingSorts extends JFrame implements ActionListener { JRadioButton bubble; JRadioButton selection;
I am going through Thinking in Java, 4th Ed and I came across the section that talks about overloading variable arguments. I tried out a piece of code from the book. (Method and class names not exactly the same).
public class Varargs { public static void m1(Character... args) { System.out.println("Character");
[code]....
In the above code, the compiler throws an 'Ambiguous for the type varargs' error. The error goes away if the first method is changed to:
public static void m1(char c, Character... args)
why there is ambiguity in the first piece of code and not the second.
Now everything works in Netbeans but running it from the command line, i get an error message ".java uses unchecked and unsafe operations".I have added a bit more code to the code above
for (int i = 0; i < args.length; i++) { System.out.println("args[" + i + "]: " + args[i]); }
Just not sure how to run it from the command line,
I am new to JAVA. I need to execute a program, based on the OS. If I am on Mac, the program is a .x and if It is on Windows the program is .exe. The program also requires a line of commands attached to it (i.e. relap5.(x) or (exe) -i inputFile -o outputFile -r restartFile -s stripFile
Here is my coding
String in = " -i ", tfIntdta.getText(); String rst = " -r ", tfRstplt.getText(); String out = " -o ", tfOutdta.getText(); String strp = " -s ", tfStpdta.getText(); if tfStpdta.contains(".csv") String run = in, rst, out, strp; else String run = in. rst, out; // I want to execute either a .x file or .exe file, depending on if I am // running the app on windows or mac run relap5.(x) or (exe) (string run goes here)
I am writing a simple program in Java, where I call a method and pass some variables (namely, min and max) as arguments. This method is recursive, so the same arguments are again passed on in each recursive call.
I need to update these variables in recursive calls so that when the calling method uses them, it uses updated values. As it might sound confusing, here is sample code :
// Function 1. void func1() { //Call func2. func2 (int hd, int min, int max, Map<String, String> map); //Other stuff. } // Function 2.
[code]....
As you can see, min and max are updated after each recursive call returns, based on conditions. However, these changes aren't reflected in original min and max, which were used by func1 while calling func2. As far as I know, this happens due to call by value mechanism being used by Java while passing arguments. If I declare min and max as instance variables in the class, my problem is solved. But, I want to know whether there's any other way to update these variables so that changes in original min and max are reflected. Yes, I can return them as an array of 2 elements each time while returning, but it didn't seem a good solution to me.
In Java code, write class called Student with the following features:
• a private instance variable int studentNumber that is initialized to zero. • a private instance variable String firstName; • a private instance variable String lastName; • a constructor which takes an integer argument and two String arguments to initializes the three respective data items. • a public method with signature equals(Student s) . . .
So far this is my code :
public class student { private int studentnumber = 0; public student () { firstname= "forename": lastname="surname": public student (integer studentnumber, string firstname, string lastname) { this.firstname= firstname this.lastname= lastname:
My question is how do i add the integer in the argument do i have to use int =? and how would i go about doing the public signature equals...
I am trying to create an array where each object includes a service description, price, and time in minutes. I have a Service class and a SalonReport class:
import java.util.*; public class Service { public String serviceDescription; public double servicePrice; public int timeMinutes;
[Code] ....
When I compile this, I get an error message that says:
SalonReport.java:8: error: constructor Service in class Service cannot be applied to given types; salonServices[0] = new Service("Cut", 8.00, 15); ^ required: no arguments found: String,double,int reason: actual and formal argument lists differ in length
What this error message means and how I can correct it? I am confused because my SalonService() method has (String service, double price, int minutes), and each object is listed in that exact order.
What I'm supposed to do is use the time class and take the command line arguments and print them as the start and end times and then calculate the elapsed time between the two. My issue (hopefully my only as I have been working on this all day now) is that I cannot call the command line arguments using LocalTime. Below is what I have so far.
public class Clock { private LocalTime startTime; private LocalTime stopTime; //default constructor-initialize startTime to current time public Clock(){ this.startTime=LocalTime.now();
I am totally new to Java. What is the purpose of this method?
Flow of the int x=3; like where does the 3 go step by step?
Passing Primitive Data Type Arguments (from oracle java tutorials)
Primitive arguments, such as an int or a double, are passed into methods by value. This means that any changes to the values of the parameters exist only within the scope of the method. When the method returns, the parameters are gone and any changes to them are lost. Here is an example:
public class PassPrimitiveByValue { public static void main(String[] args) { int x = 3; // invoke passMethod() with // x as argument passMethod(x);
I have a method that draws a polygon on the screen:
public void poly(List<Point> points) { //code }
For the usage of the method, it makes no difference whether points is an array or a List. In fact, switching doesn't even change any of the code in the method since I use a for-each loop. So, my question is, is it a better practice to use a List as an argument, or an array when the method itself doesn't care about which to use?
Primitive arguments, such as an int or a double, are passed into methods by value. This means that any changes to the values of the parameters exist only within the scope of the method. When the method returns, the parameters are gone and any changes to them are lost.
Reference data type parameters, such as objects, are also passed into methods by value. This means that when the method returns, the passed-in reference still references the same object as before. However, the values of the object's fields can be changed in the method, if they have the proper access level.For example, consider a method in an arbitrary class that moves Circle objects:
public void moveCircle(Circle circle, int deltaX, int deltaY) { // code to move origin of // circle to x+deltaX, y+deltaY circle.setX(circle.getX() + deltaX); circle.setY(circle.getY() + deltaY);
// code to assign a new // reference to circle circle = new Circle(0, 0); }
Let the method be invoked with these arguments: moveCircle(myCircle, 23, 56)
Inside the method, circle initially refers to myCircle. The method changes the x and y coordinates of the object that circle references (i.e., myCircle) by 23 and 56, respectively. These changes will persist when the method returns. Then circle is assigned a reference to a new Circle object with x = y = 0. This reassignment has no permanence, however, because the reference was passed in by value and cannot change. Within the method, the object pointed to by circle has changed, but, when the method returns, myCircle still references the same Circle object as before the method was called.