I can call a child method from a main method. If I have a parent called "Assessment", a child called "Quiz", and another child called "test". Can I instantiate an object like Assessment a = new test(); and call a method in test.
I know the method can be called if I instantiate the test t = new test() but that defeats the purpose of inheritance...
This current one is to calculate a planes holding pattern. I have to write a method to prompt user to enter speed in knots, then it converts it to km/hr. Another method to calc. pattern width using the speed, another method to calc. pattern length, than a main method which would call and print out the speed in knots, speed in km, pattern width and length.My current problem is on the second method. It works in that I can enter the values and it gives me the correct answers, however it's asking me to enter the speed twice, instead of just once. Anything I try just results in errors and won't compile.
import java.util.Scanner ;
//main method
public class TitleRemoved {
public static void main(String[] args) {
double airSpeedKm = airSpeedOts () ;
System.out.println("That speed is " + airSpeedKm + " km/hr.") ;
[code].....
I want my code to not only work, but be organized and easily readable as well, so I want to avoid bad habits.
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 have created two(displaypanel & buttonpanel) main panels in a JFrame and many child panels,one of the panel is for holding buttons and displaypanel mainly swap child panel as directed from buttonpanel, but the problem arises i cannot navigate from child panel to another child panel,
as i have made a button on one of a child panel and from button panel i add the childpanel to displaypanel.it is working but when i tried to navigate from the button which is on child panel nothing happened. "i have made a function in main form which swap the content of mainpanel (displaypanel) and in childpanel i have acces the function through object of mainform"
I can call a child method from a main method. If I have a parent called "Assessment", a child called "Quiz", and another child called "test". Can I instinate an object like Assessment a = new test(); and call a method in test.I know the method can be called if I instinate the test t = new test() but that defeats the purpose of inheritance which I'm learning in class.
View Replies View RelatedRegarding the lifecycle of servlet , in headfirst servlet i can find :
You normally will NOT override the service() method, so the one from HttpServlet will run. The service() method figures out which HTTP method (GET, POST, etc.) is in the request, and invokes the matching doGet() or doPost() method. The doGet() and doPost() inside HttpServlet don’t do anything, so you have to override one or both. This thread dies (or is put back in a Container-managed pool) when service() completes.
How can I call the doGet method of the subclass from the superclass. i am not getting this .
The idea is to create a program to add plants and retrieve plants from a Nursery. I created a class with the properties of the plants and also there is the class an Array list to keep track of the plants entered ( they will have to be printed later) (I am not too sure if adding a public class there is the best option.
The program will allow the user to pick and action and from there the code will do something. I don't want to have all the code inside 'main' The problem is in line 114.This is what I have so far.
Java Code:
package plant.nursery;
import java.util.ArrayList;
import java.util.Scanner;
/**Class to create a plant for a nursery.
public class PlantNursery
[code]....
How do I call a class within the main. For example, this is what i have in my code right now. I am trying to call the class BlackJackGame.
package blackjack
public class BlackJack {
public BlackJack() {
BlackJackGame();
}
}
I'm trying to call a method to my main method, but I can't seem to get it to work and it keeps resulting in a compile error.
import java.io.*;
import java.awt.Point;
import java.text.DecimalFormat;
import java.util.Random;
public class Chase {
public static void main(String args[]){
[Code] .....
I have been reading about methods and I do have a beginner level understanding on how they work. I was trying to mess around and make a dog calculator using methods. I ran into a small snag; I cannot get the method to call to the main or the program to compile correctly. The first code below is the original. To me it looks like (based off of some examples I looked at) there should be no problems, but NetBeans gives me a few errors. 1) line 8- "cannot find symbol, variable dogYearCalc; 2) line 18 illegal start of expression; and 3) line 22 - unreachable statement.
import javax.swing.JOptionPane;
public class KrisExample {
public static void main (String[] args) {
double dogYears = 0;
JOptionPane.showInputDialog (null,"Please enter you dog's age in human years:");
[Code] ....
Someone told me that I was calling dogYearCalc without any arguments in your main method. I take that to mean that I needed to add it to the main, so I did here:
public static void main (String[] args, double dogYearCalc) {
That got rid of my first error, but then when I tried to run the program NetBeans said that I have no main class, so switched back to the original program above.
I thought that when I calling the dogYearCalc method on line 10 was the whole purpose of using a method. It seems to me that putting it somewhere in the main is counter productive.
Can we recall the main method? I'm trying a code to recall main method (after the calling of JVM). I know this doesn't make any sense but I'm trying this just like that.
Code:
class derived {
public static void main(String args[]) {
System.out.println("Main Method class");
show();
}
static void show()
[code]....
When I try to call an object it can't find the symbol in the argument list. NetBeans says that it cannot find the movieCategory symbol when I try to call it. When I compile it to test a popup comes up that states "One or more projects were compiled with errors. Application you are running may end unexpectedly. I ran it anyways and everything runs up to the point of where it should call the object.
At this point it should get the Movie object and run the code within that, but if I put one of the categories it throws. "Exception in thread "main" java. lang.RuntimeException: Uncompilable source code - Erroneous tree type: <any>at MovieApp.main(MovieApp.java:33)Java Result: 1"
From my understanding to call an object it requires objectName.methodName(argumentList). Here is my Main method
/**
*This application will store a list of 100 movies and display them by category
*/
import java.util.Scanner;
public class MovieApp
{
public static void main(String args[])
{
//Displays <code>String</code> welcome message
System.out.println("Welcome to the Movie Application.");
System.out.println("There are 100 movies in the list.");
System.out.println("What category are you interested in?");
System.out.println();
[code].....
I have a frame which I want to load an applet inside it. Here is the code i have in my main method:
MyApplet myApplet = new MyApplet();
myApplet.init();
myApplet.start();
javax.swing.JFrame window = new javax.swing.JFrame("myApplet");
window.setContentPane(myApplet);
window.setDefaultCloseOperation(javax.swing.JFrame.EXIT_ON_CLOSE);
window.pack();
window.setVisible(true);
But I get an exception:
Quote
Exception in thread "main" java.lang.NullPointerException
at java.applet.Applet.getCodeBase(Applet.java:169)
at MyApplet.init(MyApplet.java:78)
at Intro.main(Intro.java:68)
Java Result: 1
I'm working with Libgdx but I have a basic java question. I'm trying to access the overridden methods from and interface in another class via a call but I'm not sure how. This is what I've got so far :
Java Code:
public interface Controller {
public void show ();
}
public class MainActivity extends AndroidApplication implements Controller {
@Override
public void showAd(boolean show) {
System.out.println("TEST");
[Code] ....
Right now this code returns a null pointer at the call.
I have two classes, MonsterGame (shown below) and Monster. Monster has a public accessor method to get it's private character variable, which represents the first character of the name of the Monster in question.
I'm just a bit confused as to why am I unable to cycle through the array of Monsters I have in the MonsterGame class and call
m.getCharacter(); (pretty much the last line of code)
public class MonsterGame{
private static final char EMPTY_SQUARE = ' ';
private char[][] gameBoard = new char[10][10];
private Monster[] monsters = new Monster[4];
private int maxXBoardSize = gameBoard.length -1;
private int maxYBoardSize = gameBoard[0].length -1;
[Code] ....
I understand that there need to be instances of objects to call methods, but is that not the case here? the Monster objects are have already been created, no? Do I need to create an index for the array? is the for loop not enough?
So I'm just a little unclear about this, but how would I call methods from the 'top' of an inheritance chain? I say 'top' because Object is the top... E.g.:
public class AClass {
public void myMethod() { ... }
}
public class BClass extends AClass {
public void myMethod() { ... }
}
public class CClass extends AClass {
public void myMethod() { ... }
}
Assuming that BClass.myMethod() completely overrides AClass.myMethod() (so that there is no call to super.myMethod() in BClass.myMethod()) How can I call AClass.myMethod() from CClass.myMethod()?
How should I call my findSmallest method in the main class.. Here is the code:
public class Tester {
public static void main(String[] args){
try {
BinaryTree<Integer> myTree2 = new BinaryTree<Integer>();
myTree2.insert(5);
myTree2.insert(2);
myTree2.insert(7);
[Code] ....
So the question is what kind of parameter I should pass in myTree2.findSmallest()??? Here is my findSmallest method..
public E findSmallest(Node<E> parent){
if(parent.left.left == null){
E returnValue = parent.left.data;
parent.left = parent.left.right;
return returnValue;
} else {
return findSmallest(parent.left);
}
}
Does child class gets a copy of the methods and variables of parent class?
public class test1 {
public static void main(String a[]) {
Child c = new Child();
c.print();
[Code] ....
why is the output 1?
Basically I'm trying to code this program but I keep getting error can't be applied to given types. I know it has to do with my method trying to be called by an array, but I'm just kinda lost.
Write a program that prompts the user to input cash amounts and use a method to calculate the average amount for a week given 7 inputs of daily cash intake amounts for a cash register. Use an array to store the values. Recall that average is the sum of the values divided by the number of values. The method should take argument(s) of type double and return average weekly cash amount as a double.
Make sure you test your program using the test data given below and calls the averageCash() method defined above passing in the values. Verify that the input values are greater than or equal to 0. Negative numbers are not allowed. Output the values used and the averageCash value.
import java.util.*;
public class ArrayHandout {
public static void main(String args[]) {
int[] a=new int[6];
Scanner sc=new Scanner(System.in);
[Code] ....
eg: "Sourdough".toUpperCase();
I guess this is actually a 2-part question:
- How does this work? (nothing seems to be passed through the parameter, so how is it that the value or variable is manipulated in this fashion?)
- How would I create a method that does something similar? (ie. adjusting a variable without having it passed through the parameters)
I am confused when it is proper to use an application with multiple entry points, or I guess an application with multiple interconnected modules. I have a network application (Netty) as well as a web application (spring). I can bundle them together, in effect tightly coupling them together, or I can modularize them to operate interdependently of each other while still working together to make the application whole.
Is there any specific reason for making an application a single entity vs multiple entities? Is it "desired" to have a self contained application (eg. One main method)?
In this project each individual will create a data analysis program that will at a minimum,
1) read data in from a text file,
2) sort data in some way,
3) search the data in some way,
4) perform at least three mathematical manipulations of the data,
5) display results of the data analysis in numeric/textual form, and
6) display graphs of the data. In addition,
7) your program should handle invalid input appropriately and
8) your program should use some "new" feature that you have not been taught explicitly in class.
(Note: this is to give you practice learning new material on your own - a critical skill of today's programmer.) If you do not have a specific plan in mind for your project, below is a specific project that meets all of the qualifications as long as 7) and 8) are addressed in the implementation.
Everything is done except I need to call my methods in my GradeTester.
GradeBook:
/**
*This class creates an array called scores.
*This class determines the length of the array scores and determines the last grade in the array scores.
*This class sorts the array using a bubble sort, and searches the array.
*This class calculates the mean, standard deviation, and the median of the grades in the array scores.
*Once the grades in the array is sorted, the class then calculates the highest and lowest grades in the array.
*/
public class GradeBook {
public final int MAXARRAY_SZ = 20;
double [] scores = new double [MAXARRAY_SZ];
int lastGrade = 0;
double mean = 0;
[Code] ....
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]....
a. Create an application named ArithmeticMethods whose main() method holds two integer variables. Assign values to the variables. In turn, pass each value to methods named displayNumberPlus10(), displayNumberPlus100(), and displayNumberPlus1000(). Create each method to perform the task its name implies.
b. Modify the ArithmeticMethods class to accept the values of the two integers from a user at the keyboard.
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]...
I am assigned to create a program "Simpletron" that the only language understands it is Simpletron Machine Language or SML. I figured out the most but I get the message "No main methods, applets, or MIDlets found in file" when compiling the program. I pasted my program so that you can see.
//A Simpletron computer simulator */
import javax.swing.*;
import java.text.DecimalFormat;
import java.awt.*;
import java.awt.event.*;
[code]....