I am very Java illiterate and I need to know how would i set all the variables in the first class to null or 0 to make a new method to clear everything.
import java.util.Arrays;
import java.util.Scanner;
public class studentMethods
{
private double totalScore;
private int count;
[Code] ....
package com.example.imc;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
[Code] ....
After installing JDK, I extended my system path to include C:Program FilesJavajdk1.8.0in. However, javac is only recognised if im in directory C: but that doesn't apply to the Java (run) command which works when Im in the sub-directory that has my .class file. Is there a way to make javac work when Im in a sub-directory?
View Replies View RelatedI have wrote the method delete turtle below. Which is part of turtle collection (Hashmap)
public void deleteTurtle(String name) {
Iterator iterate = turtles.keySet().iterator();
while(iterate.hasNext()) {
String key = (String)iterate.next();
if(key.equals(name)) {
iterate.remove();
} else {
setErrorMessage("notFound");
}
}
}
I need to now modify it so the method ensures that the turtles shape collection is cleared before the Turtle object is deleted.
Take a look at this screenshot... my java integrated devlopment envirnment is telling me I have a null pointer on a line with three variables ALL which were initialized.
I thought a null pointer was called when a variable doesn't get initialized.
Edit: Here is the java file and resources being used: [URL]
I'm writing a simple program in which I have a super class Person, inherited by the subclasses Customer and Employee (they inherit the variables ID, name and surname).
Java Code:
public class Person {
int id;
String name;
String surname;
public Person () {
[Code] .....
However the problem is here: when I try to get the variables ID, name and surname through my main class, they fail to return (0,null,null). Why is this? I have get-Methods in my subclasses which should return the super variables, but they are not.
Java Code:
public String getUser() {
return username;
}
public String getName() {
return super.name;
} mh_sh_highlight_all('java');
import javax.swing.*;
import java.awt.Container;
import java.awt.FlowLayout;
import java.awt.GridLayout;
import java.awt.event.*;
[code]....
My issues is at the bottom, I can't get the clear button to clear, well it clears but it also show the JOptionPane. I couldn't find the edit button on the page
Why 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've looped a method 14 times, each time it focuses on a different person and how many oranges he/she has eaten. I now want to calculate the total amount of oranges eaten and exactly how many oranges are eaten on average, how can I do that?? the amount of oranges eaten is variable, they are determined by what number the user types in.
View Replies View RelatedAlright, 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'm having trouble setting up a test for my combination method.Here's the method (It basically finds the most amount of characters that both substrings share and combines the two using the number of shared characters as a breaking point):
public static String combination(String str1, String str2, int overlap) {
assert str1 != null : "Violation of: str1 is not null";
assert str2 != null : "Violation of: str2 is not null";
assert 0 <= overlap
&& overlap <= str1.length()
&& overlap <= str2.length()
&& str1.regionMatches(str1.length() - overlap, str2, 0, overlap) : ""
+ "Violation of: OVERLAPS(str1, str2, overlap)";
[code]....
package com.simbaorka101.te.gui;
import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JScrollPane;
import javax.swing.ScrollPaneConstants;
import javax.swing.event.DocumentListener;
[code]....
This is my frame class, now I want to be able to change the name of the frame, and get the name with frame.getName() in another class. But I'm not sure how to do this, i tried making a new frame in that class but i feel it's just another frame and not the one i made, also tried something like
public JFrame getFrame(){
this.getFrame();
}
and few variations but it was wrong.
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?
I am working on a project which manages an airport's airplanes and flights based on user input. The method printFlights() - lines 133-134 - is returning null and I can't figure out why. The method is supposed to print information about each flight. The logic is identical to the printPlanes() method which is working successfully.
View Replies View RelatedI am trying to return an array and I keep getting a null error. The below class sets the material numbers into an array and should return that array if called :
public class Jobs {
private int[] materialsNumber;
//change to parts and create another class that gets the materials for the parts
public int[] job1() {
materialsNumber[0] = 11960120;
[Code] ....
I later try to call the method. The program executes but stops after I println "test in loop"
public class PurchaseOrdersToParts {
private Jobs job = new Jobs();
int[] getPartsForPurchaseOrder(BigDecimal purchaseOrder) {
System.out.println("inside getparts");
BigDecimal testNum = new BigDecimal(123.0);
[Code] ....
This is the method that is calling the method in the GenerateOrdersToParts class
private PurchaseOrdersToParts purchaseOrdersToParts = new PurchaseOrdersToParts();
@Inject
PoRepository poRepository;
public GenerateShopJobTickets() {
[Code] .....
The getGraphics() method in my constructor is returning a nullPointerException and I can't figure out why. This class is extending a JPanel and I thought calling super() would fix it because it makes sense that the JPanel would initialize its graphics object in the constructor, but that didn't fix it. The line that produces the error is in bold. I've narrowed it down to the getGraphics() method is returning null, so the next line that calls the graphics object is actually the one that produces the error.
int leftMargin = 2, rightMargin = 2, topMargin = 2, bottomMargin = 2;
int lineSpacing = 1;
int currentX = leftMargin, currentY = topMargin;
Font defaultFont, customFont;
public HTMLFrame(){
super();
[Code] ....
print(String) is a method I made that draws lines of text on the graphics object, similar to System.out.println(String) in the command prompt.
I just want to be able to read type and weight in the Letter class I created (I created read out messages to check in the Letter class). I am able to read it with in the Mail class.
package org.mailprice.postage;
import java.util.Scanner;
public class Mail {
static Letter letter;
[code]....
I'm trying to call the grade.processFile method from the main method but I'm getting this Error below. I'll post my code which includes the main method and the class underneath the error message:
Exception in thread "main" java.lang.NullPointerException
at java.io.FileInputStream.<init>(FileInputStream.jav a:130)
at java.util.Scanner.<init>(Scanner.java:611)
at MyGrades.processFile(MyGrades.java:49)
at myGradesMain.main(myGradesMain.java:19)
import java.util.Scanner;
import java.io.*;
[code]...
I have a class of Date with a constructor with 3 parameters in it. Those 3 parameters are int data type just to enter month, year, day.
I have another class called Author which has a constructor of Date diedDate; as a parameter passing to the Author constructor.
I was asked to call the Date parameter is null, call the default constructor but I thought for the Date parameter I could only enter something like 0,0,0 instead of typing in null, null, null because null is for String data type isn't it?
Now that I have figured out how to return a single variable from a method I am on to the next step, I need to return 2 or 3 variables from a method. I have searched the internet on how to do this to no avail (am I doing the wrong search? I do not know) but what I need to do is return a second (and eventually a third variable)
Here is what I have
private static String Engine() {
String engine = "";
int enginePrice = 0;
System.out.println("Choose a engine size:");
System.out.println("[4] cylinder");
[Code] .....
Which does not work.
Can method variables be shared between users?
I was asked this on an interview and I didn't know what to make of it.
I will like to add to the questions about constructors and its this. I have a class A with a constructor, i have a class B which initialize the constructor. also i have a class C which needs a variable in class A but doesn't need to initialize the constructor of A. the question how do i access the variable of class A without initializing the constructor.
View Replies View RelatedI wanna know which is the best way to access a variables within a class ...
Using direct access or using the variable accessor ...
Example :
public class Numbers{
private int n1;
private int n2;
public void setN1(int n){
n1 = n;
[Code] ....
I've a vertical-bar-delimited file where most elements contain text, some contain whitespace, and some are empty. Examples:
62RG|fe|Pencil Financial Group, LLC||doug@pencil.com|||85637889|Cross, Ben|bcross@godaddy.net|Bernard|Cross|Ben||315 One Tree Hill Terrace|Lafayette|LA
62RG|fe|Pencil Financial Group, LLC||tracy@pencil.com|||13658734|Dustin Cardwright|dcart@motorola.com|Dustin|Cartwright|||| |LA
which I parse and store with
String str_arry = innline.split( "|", 17);
lisst.add( new Contact( str_arry));
and my Contact class has the constructor
public Contact( String[] str_arry) {
for( int ii = 0 ; ii < str_arry.length ; ii++ ) {
if( str_arry[ii].matches("^s+$")) {
str_arry[ii] = null;
System.out.println("hit a null");
[Code]...
I expect the for-loop in the constructor to find any elements containing whitespace characters and set them to null for subsequent assignment.And when the code runs I do see some hit-statements pop up, so the detecting part is working.
But when I then process the list and access a Contact object and test fields for nulls I don't find any ie
if( aContactObj.getfFCity() == null) System.out.println("city is null");
never prints when it should.
What's the trick? Or is my approach wrong and if so what should it be?
This program should create a GUI that has 5 classes together on a grid layout. The problem that I am having is that the user input class has the input for kwh, hours, and gallons. I am having problems getting that information from the user input class to the totals class.
user input class:
package applianceutilitycalculator;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.Scanner;
import javax.swing.*;
[code].....
The totals class should take the info from the kwh hours and gallons and do the math to get a total and display it in a JTextField(?).
When creating a class with a constructor, why does one have to create private variables (attributes) to be used as parameters by the object? The object's parameters will be set to be exactly equal to the private variables (attributes), so what is the point of having the private variables (attributes) Why are both private variables (attributes) and parameters needed when they are set to be equal each other anyway?
View Replies View Related