How To Create Object To Be Null If Class Constructor Parameter Is Int
Mar 8, 2015
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?
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Mar 4, 2014
Instructions
Create a WordCounter class with a constructor that takes a file name as a parameter
The class should have two fields: one for the file name and one for a HashMap to store word count information
The constructor should call a private method, countWords, that reads in the file and counts the word frequencies
The class should contain a get method for each field, as well as a print method that prints out the map in the following format:word:frequency
When printing, the map should be sorted by either the word order or frequency (Hint: see Collections.sort)
You should include the sample text file on Blackboard. This is what i got so far
Java Code:
import java.io.File;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.Scanner;
public class WordCounter
[Code] ....
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Mar 12, 2014
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?
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Dec 13, 2014
Assuming that we have two classes B and C which inherit from class A. What is the best way to pass a parameter from an object of class B to an object of class C by the use of class A without using static variable and without defining a get function in B?
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Apr 19, 2014
I was practicing my java skills and came across an exercise in which a non parameter constructor calls a two parameter constructor. I tried a few searches online but they all came back unsuccessful. This is the part I am working on:
public PairOfDice(int val1, int val2) {
// Constructor. Creates a pair of dice that
// are initially showing the values val1 and val2.
die1 = val1; // Assign specified values
die2 = val2; // to the instance variables.
}
public PairOfDice() {
// Constructor that calls two parameter constructor
}
I tried calling the two constructor using the line "this(val1, val2)" but I get an error because val1 and val2 are local variables.
Then I tried to use the same signature: "this(int val1, int val2)" but that didn't work either.
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Mar 30, 2014
what have I done wrong n the following code? I'm trying to create a new instance carte of object Carti using the constructor and then to insert a row into a table created with SQL.The error I'm getting is:
Exception in thread "main" java.lang.NullPointerException
at Carti.Carti.InsertCarti(Carti.java:103)
at Main.main(Main.java:37)
Java Result: 1
BUILD SUCCESSFUL (total time: 28 seconds)
The line Main.main(Main.java:37) is when I try to insert the row.
The line Carti.Carti.InsertCarti(Carti.java:103) is when I do the
PreparedStatement st = conn.prepareStatement("insert into Carti (Id,titlu"
+ ", descriere, autor, editie, anPublicare) values (?,?,?,?,?,?)");
Here is the code (Main and Carti Classes)
import Carti.Carti;
import Imprumut_Carti.Imprumut_Carti;
import Membrii.Membrii;
import static com.sun.org.apache.xalan.internal.lib.ExsltDatetime.date;
import static com.sun.org.apache.xalan.internal.lib.ExsltDatetime.date;
import java.sql.SQLException;
import java.text.DateFormat;
[code]....
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Aug 28, 2014
can we pass private final class object to another class constructor?
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Feb 28, 2014
The one problem in my book was to create a constructor for different shirt features, which I did and ran successfully. Out of curiosity, I also added other methods to see if it would run if the parameters were different from the constructor. It keeps giving me a constructor error. So, my question is, am I able to create a class that uses a constructor with parameters and other methods without errors? I'm guessing there's no reason to since it would be wasted space since the constructor could do it but was just curious if it's possible.
Is everything from the constructor down (in the class) and Shirt.oneShirt (in the main) just a waste of time?
Here's my example:
public class Shirt//class name.
{
int collarSize;//data field.
int sleeveLength;//data field.
int pocketNumber;//data field
public final static String MATERIAL = "cotton";//final data field for material.
public Shirt(int collarSize, int sleeveLength, int pocketNumber)//start of constructor.
{
[Code]...
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Apr 22, 2015
How to create object for "class B" and call the "function_B" from other different class D where class D has no connection with class A? Here is my program.
public class A(){
void print(){}
}
class B{
void function_B(){}
}
class C{
void function_C(){}
}
Here, A, B, C are in the same package. But class D is in different package.
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Jun 10, 2014
Design a class named Person and its two subclasses named Student and Employee. Make Faculty and Staff subclasses of Employee. There is also a MyDate class as explained below. A person has a name, address, phone number, and email address. A student has a status (freshman, sophomore, junior, or senior). Define the status as an integer which can have the value 0 (for "Freshman"),
1 (for "Sophomore"),
2 (for "Junior"), and
3 (for "Senior"),
but don't allow the status to be set to any other values. An employee has an office, salary, and dateHired. The dateHired is a MyDate field, which contains the fields: year, month, and day. The MyDate class does not explicitly inherit from any class, and it should have a no-arg constructor that sets the year, month, and day to the current year, month, and day. The MyDate class should also have a three-argument constructor that gets three int arguments for the year, month and day to set the year, month and day.
A faculty member has office hours and a rank. Define the rank as a String (for values like "Professor" or "Instructor"). A staff member has a title, which is also a String. Use data types for the fields as specified, or where one is not specified, use a data type that is appropriate for the particular field. Write a test program called TestEveryone.java that creates a Person, Student, Employee, Faculty, and Staff object, and invoke their toString() method (you don't need to call the objects' toString() method explicitly).
Note: Your MyDate.java class is the object class that your dateHired field is created from in the Employee.java class.
Do not use the Person, Employee or Faculty classes defined on pages 383 and 384 of the book. Create new ones.Here is the code I have so far concerning the employee and MyDate.
public class Employee extends Person {
private String office;
private double salary;
//private MyDate dateHired;
//7 argument constructor for employee
public Employee(String name, String phoneNumber, String email, String address, String office, double salary /*MyDate dateHired*/) {
super(name, phoneNumber, email, address);
[code]....
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Jan 2, 2014
So, I am learning Swing, and Swing Layouts. I just came across a really confusing (for me) line of code.
Java Code:
setLayout(new BorderLayout()); mh_sh_highlight_all('java');
So, this is weird for me because I don't really understand why the BorderLayout class constructor is being initialized as a parameter for the setLayout..
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Jul 18, 2014
Why we can't create object of abstract class ,when we can create its constructor?
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Dec 11, 2012
I know that System is a final class and it cannot be instantiated, out is a static final variable of type PrintStream in System class and println is a method in PrintStream class.Still I don't understand why we use System.out to call println() method.To my knowledge a method can be called using an object reference, in case of static behaviors we use classname. Then why here we are using System.out.println? Can't we just create an object of PrintStream class and call the println() method as PrintStream class can be instantiated.Are there any ways of calling a method apart from those I know(I have mentioned above what I know)?
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Oct 5, 2014
Animal ob1=new Lion();
Here we create ob1 for Animal class or Lion class.
public abstract class Animal {
public abstract void eat();
public void breathe(){
[Code] ....
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Apr 16, 2014
I'm curious why ACM isn't letting me create an object from a different class, maybe I am missing something?
my main class:
import java.awt.Color;
import acm.program.*;
import acm.graphics.*;
public class MyClass extends GraphicsProgram {
private static final int WINDOW_W = 500;
private static final int WINDOW_H = 500;
[code]....
I have also noticed when trying to extend 'ConsoleProgram' it does the same thing with line printing (except when using system.out).
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Mar 29, 2014
public Unit(String code, String name)
{
enrolStudent(student);
this.unitCode = code;
this.unitName = name;
}
public void enrolStudent(Student newStudent){
students = new ArrayList<Student>();
newStudent = new Student(24662496, "Kingsley", " Iwunze");
students.add(newStudent);
}
how can I call this enrolStudent() method on this Unit constructor in another class when I create a new Unit. all I need is to enroll students in units when units are created. below is my create unit method.
public void createUnits( ){
units = new ArrayList<Unit>();
units.add(new Unit("FIT2034", "Java Programming 2"));
units.add(new Unit("FIT2024", "Software Engineering"));
units.add(new Unit("MAT1830","Discrete Maths"));
unit.enrolStudent(new Student(25486321, "Julia", "Garcia"));
unit.enrolStudent(new Student(44589736, "James", "Olivia"));
unit.enrolStudent(new Student(47852103, "Lucky", "Thyriod"));
}
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Feb 26, 2015
I've been writing classes over and over for school. So I create a class outside of my main class. I create a new constructor and then create objects from my main class. I hope that makes sense. So i use methods in that class to work with the object. So I have an object name I've created <dot> method name. So I can create objects and then use methods from the class, but I'm wondering can I create a method in my main class and use it on that object? I don't understand how to do that.
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Sep 7, 2014
I'm getting constructor null pointer exception but i don't know what has gone wrong...
private int capacity; // maximum capacity of the board
private double minimum; // minimum distance of the flyer
private SortedLinkedList sortedList;
private int size = 0;
public ScoreBoard() {
capacity = 10;
minimum = 0.0;
sortedList = new SortedLinkedList();
[Code] ....
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Aug 8, 2014
i want to pass an object of type Software to assign it to a computer from Computer class...
i should note that computer and software are arrays of objects thats the variable and method to set software in Computer class
private Software[] software;
public void setSoftware(Software software,int index){
this.software[index]=software;}
note: the user choses the a computer from a list and a software as will
for example the program will show the user 2 computers
0 for computer: apple, Model: mac mini, Speed: 2.8
1 for computer: sony, Model: vaio, Speed: 2.2
the user enters the index he wants then the program will show a list of software to add to the computer selected
the error I'm having is run time error Exception in thread "main" java.lang.NullPointerException and it points to these 2 lines
1.comp[Cch].setSoftware(software,Sch);
2. the method setSoftware
every thing is running correctly but this step above
Cch= the chosen computer index
Sch= the chosen Software index
why am i getting an error and how to fix it?
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Jan 3, 2015
I have a method that accepts as a parameter an object:
public void addClient(Client c){ }
Client is a class which has a constructor that has two String parameters:
public Cliente (String name, String lastname){
this.name = name;
this.lastname = lastname;
}
In the main add a Client in this way:
addClient(new Cliente("first", "second"));
Now, i have an array of Client, so I would like to enter within this. Example:
public void addClient(Client c){
for (int i = 0; i<client.length ; i++) { // client is an array of Client object
client[i] = c; // Enter a c in the array, but does not work!
System.out.println("test "+clienti[i]); // print Client@15db9743
}
}
I have used the println for check if worked insertion, but the result shows no
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Mar 8, 2015
I have an object that has an instance of another object class as its parameter :
CombinationLock oneHundred = new CombinationLock(28,17,39);
Locker Mickey = new Locker(100, "Mickey", 3, oneHundred);
This is for a locker, which has a combination assigned to the student. Within the locker class I have the following constructor:
public Locker(int locker, String student, int numberOfBooks, CombinationLock combo) {
this.locker = locker;
this.combo = combo;
this.student = student;
this.numberOfBooks = numberOfBooks;
}
combo is the private CombinationLocker object I created within the Locker class. Do I need to pass the combo object on to the CombinationLock class? For reason, I do not comprehend, the combination password from the main class is not passing through to the CombinationLock class, and the combination values are all zero.
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Oct 29, 2014
I'm working on a method that would parse the value of the array of object that I passed through a parameter. I would like to ask if making Object as a parameter is doable. Let's say I have a class Student and Teacher. I created a class the would handle the sched and name it class Schedule and extend this class to the Student and Teacher. Now I want to have a function that will accept an array of Schedule from either Student and Teacher, what ever object I will pass in the parameter. I know its easy to just make a method with a separate parameter of my classes but im looking for a more dynamic code.
class Student extends Schedule{
//variables here for student
}
[code]
class Teacher extends Schedule{
//variables here for teacher
}
[/code]
private void parseObject(ArrayList<Object> objct){
Schedule temp = objct.get(0);
//there is no error in this part
}
Now when i will try to use the function and pass a data, it will not accept since my parameter should be an array of object. How would I twist dis one?
ArrayList<Student> temp_student = new Array....
parseObject(temp_student); // it will not accept my parameter, how would i make it as an object
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Mar 9, 2015
so i have this question where it wants me to create a recursion method that takes ONLY THE ARRAY as a parameter, and without using loops or static variables inside the method, and then the method returns the smallest value in that array. However, i tried making the simple if statements where i compare the first element of the array with the second element using the length of the array and decreasing it to get the next elements and compare it again by calling the recursion method, but the problem is when i call the method again, the length does not decrease, even if i store it in a variable, the variable will initialize itself again, and the length wont change.
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Feb 7, 2015
In my book for learning java, one of the questions asks us to create a method header named convertTOKM that takes an int parameter, which is the number of miles, and returns a double value for the converted value in kilometers. I made one, but wanted to know if I was right in any way.
Here it is:public double convertTOKM(int miles, double kilometers){
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Aug 1, 2014
So i declared a class in main class but it seems there's error when i compile:
constructor xx in class xx cannot applied to given types
This is my java class:
public class trainer extends person{
String classType;
public trainer(String name, String gender, String address, int id, String classType) {
super(name,gender,address,id);
this.classType=classType;
[Code] ....
And this is the way i declared in main class:
trainer tr = new trainer();
And what i want to do is:
tr.toString();
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Jun 6, 2014
When using Java Code:
Scanner scan = new Scanner(system.in) mh_sh_highlight_all('java');
Why do we put System.in in the constructor? What purpose does it serve and why can't we just not use it?
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