Get And Set Methods For Instantiated Object?
Oct 17, 2014
I am being told to (assignment) create a new Bread Object in another class than the original. But after that it is asking for get and set methods. Get and set methods of what? It's parameters?
class Bread
{
private static String breadType; //private field to hold bread type
private static int numberOfCaloriesPerSlice; //private field to hold calories per slice
public static String getBreadType() //get method
{
return breadType;
[code]....
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Dec 1, 2014
I have a Member class and a Player class. Players extends Members. I know that player will have all the methods of Member but I was wondering how I could link a player object directly to a member object.
public class Member(){
String name,surname;
public Member(String name, String surname){
this.name = name;
this.surname = surname;
[Code] ....
What im looking for is the p1.getName() to return John. Can I do something within the Player class for it to inherit from a Member object...
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Feb 14, 2014
Interfaces are 100 % abstract classes.They cannot be instantiated.Their sole purpose is to be implemented.So why does the following code works just fine while it is attempting to instantiate an interface.
interface TestA { String toString(); }
public class Test {
public static void main(String[] args) {
System.out.println(new TestA() {
public String toString() { return "test"; }});
}
}
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Jun 5, 2014
I have a JSF bean which is request scope and corresponding JSF UI page. when user tries to open this page, we are getting exception 'Cannot instantiate user.java class <default constructor>'. This does not come always. It comes very rarely. JSF version is 1.2
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Mar 19, 2014
Let's say I have a Junit4 class FooTest.java and variable token. At some point in class the token gets instantiated.
Java Code:
public class Foo {
private String token;
@Before
public void setUp() {
// serious is steps to get the application to a certain state where token can get extracted
....
token = extractToken();
}
} mh_sh_highlight_all('java');
Now I have another class User.java where I need to use this token. Can I inject this token somehow into that class? There is no relation between Foo and User. I can't use Provider method in the configure file because extraction of the token depends on certain system's state and can't be called anywhere anytime.
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Jan 16, 2014
We know that all classes in Java extend the Object class. But methods in Object class are declared as public.I think if they were declared as protected, then also there wont have been any issue. So, what is the reason behind making them as public?
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Oct 14, 2014
Scanner in = new Scanner(System.in);
ArrayList<rand> selectedRand = new ArrayList<Rand>();
selectedRand.add(new Rand(in.nextLine()));
I have created the most minimal code for creating an array list. I was wondering what the basic syntax of accessing objects methods that are within an Array List. So if I was to trying and get a method such as [.returnValue,] how would this look within a Rand object that is declared in a Array List Since you cannot simply declare a new Rand object and say:
newRandObject.returnValue();
And you must go through the actual slotted portion of the array list. I have searched the web and my text book for an example however none are provided.
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Jun 30, 2014
so, i was reading my java book and learning about objects and methods and it starts talking about Encapsulation and mentions that it's good practice to set instance variables as private and instead of accessing the instance variables directly, we should create a set method and get method to get and set the stuff we want to pass to the class containing the object...
for example, in this class, we're passing the integer 70 for object dog one and integer 8 for object dog two for the dog class... and these these 2 integers are sent to the setsize method so we're not accessing instance variable size directly.
i dont quite get it though....if we the programmer are the one deciding what size the integer is for the dog, and the setsize method takes the one.setSize(70) or (8) and puts them in setsize(int s) as s... but only to copy that integer stored in s back to private int size.... why do we even need to bother with making these two extra methods such as setSize, getSize?
in the book it says that... well what if the code gets into the wrong hand and someone writes something like one.setSize(0) then you would get a dog with size 0 which is essentially illogical. but then again, i'm the programmer, and i am the person who writes the code and passing the right integer.The reason for public and private... that part i understand... i can see why if a variable's data can get changed amidst the code during calculations and you dont want it to directly change the original variable and have it mess up the code, but this code from the book just a bad example of demonstrating the reason? since we manually pass the information ourselves and passing it to method setSize... and all setSize does is stores it in another integer, only to copy it right away to size (which is the original private variable we were tryign to protect?
Any simple code to demonstrate how the code might end up changing an instance variable and why we would want to protect it by using private?
class GoodDog {
private int size;
public int getSize() {
return size;
}
public void setSize(int s) {
size = s;
[code]...
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Jun 15, 2014
Check out the following basic code (assume that dog has a method called bark):
Dog d = new Dog();
Object o = d;
o.bark(); // error
But why? Isn't o just a pointer to a memory address which has the dog object? If so, why can't the compiler see that the object has a method called bark? Or, to ask the question another way, why is Java designed to check the object reference to see if the method exists instead of the object itself?
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Jan 8, 2014
why interfaces inherit prototype of all the non final methods of the object class in itself? Object class is parent class of all the class and Interface is not the class.
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Mar 9, 2014
I have a project where I must sort a collection of songs by a number of fields: year, rank, title and artist. in the project, we must use certain methods and we cannot add others without getting marked down. Here are the specific requirements:
Sorting
The -sortBy option will cause the output to be sorted by a particular field. If this option is specified, the output should be ordered according to the field named. If there are ties, the tied songs should appear in same order in which they were in the input file. If no -sortBy option is specified, the output should maintain the order of the input file.
public void sortYear()
Order the songs in this collection by year (ascending).public void sortRank()
Order the songs in this collection by rank (ascending).public void sortArtist()
Order the songs in this collection lexicographically by artist (ascending, case-insensitive).public void sortTitle()
Order the songs in this collection lexicographically by title (ascending, case-insensitive).
Here is the relevant code:
SongCollection Class
Java Code: import java.io.File;
import java.io.FileNotFoundException;
import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;
import java.util.*;
[code]....
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Feb 24, 2014
I've tried a couple ways to do it, and they don't work. I'm aiming for functionality like I got with the regular for loop, but from an enhanced for loop. Is this simply beyond the scope of an enhanced for loop, or am I just not getting the right syntax?
TestObject to1 = new TestObject("first", 11);
TestObject to2 = new TestObject("second", 12);
TestObject to3 = new TestObject("third", 13);
TestObject to4 = new TestObject("fourth", 14);
TestObject to5 = new TestObject();
List<TestObject> testList;
testList = new ArrayList<TestObject>();
[code]....
The TestObject class is simply an int and a String, with getters getInt and getString. It all works fine with the regular for loop.
edit: I should probably mention that I know what I have in the enhanced for loop now will only display the class name and the hash. I've tried adding the .getString and .getInt, and tried a few other ways to make it work. I just reverted to this because it compiles and runs
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Dec 10, 2014
This program is basically complete. It compiles and runs. It is a college course assignment that I pretty much completed but for the last part in which I'm suppose to change the values of all fields and display the modified values using a toString method. Modifying the values of the fields is where I am stuck. I don't think I need to create a new text data file to do this. The instructor only asked that all the values of fields be changed and this was the last part of the assignment so I don't think it involves creating additional ObjectOutputStream and ObjectInputStream objects. I'm getting a NullPointerException error on line 161.Here is the code. I'm also including the input data file.
//create program so that objects of class can be serialized, implements interface Serialiable
//create constructor with 4 parameters with accompanying get and set methods, Override toString method
//create text file with 5 records, create Scanner object,ObjectOutputStream, and ObjectInputStream
//create new ItemRecord object, change values of all fields in ItemRecord object using object's set methods
//modify ItemRecord object using toString method
[hightlight =Java]import java.io.Serializable;
public class ItemRecord implements Serializable
[Code] .....
This is the error message:
----jGRASP exec: java ItemRecordReport
Item Cost Quantity Description
Number
A100 $ 99.99 10 Canon PowerShot-135
A200 $149.99 50 Panasonic-Lumix T55
A300 $349.99 20 Nikon- D3200 DSRL
A400 $280.99 30 Sony- DSC-W800
A500 $ 97.99 20 Samsung- WB35F
Exception in thread "main" java.lang.NullPointerException
at ItemRecordReport.main(ItemRecordReport.java:161)
----jGRASP wedge2: exit code for process is 1.
----jGRASP: operation complete.
Here is the data file:
A100 99.99 10 Canon PowerShot-135
A200 149.99 50 Panasonic-Lumix T55
A300 349.99 20 Nikon- D3200 DSRL
A400 280.99 30 Sony- DSC-W800
A500 97.99 20 Samsung- WB35F
Here is the data file for the modified field values.
B100 98.00 10 ABC1010
B200 97.00 15 DEF1020
B300 96.00 10 GHI1030
B400 95.00 05 JKL1040
B500 94.00 01 MNO1050
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May 24, 2015
The question pretty much says it all, but I tasked myself with creating a program about lemurs. There are multiple class files in this program. In the below code snippet, I have my TreeLemur.class which extends to the Lemur.class which extends to the Mammal.class. However, when I create a Tree Lemur object in the main program, it is returning null consistently from certain methods. What am I doing wrong here?
TreeLemur.class :
public class TreeLemur extends Lemur {
private String groupSize;
private String diet;
private String fur;
public void setGroupSize() {
groupSize = "
Group Size: Large";
}
[Code]...
As of yet, I'm just trying to get Tree Lemur working properly to continue with creating the other if-branches within the main program.
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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.
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Mar 28, 2014
Create an equals method that takes an object reference and returns true if the given object equals this object.
Hint: You'll need 'instanceof' and cast to a (Geocache)
So far I have:
public boolean equals(Object O){
if(O instanceof Geocache){
Geocache j=(Geocache) O;
if (this.equals(j)) //I know this is wrong... but I can't figure it out
return true;
}
else return false;
}
I think I have it correct up to the casting but I don't understand what I'm suppose to do with the this.equals(). Also I'm getting an error that I'm not returning a boolean... I get this all the time in other problems. I don't get why since I have to instances of returning booleans in this. "returns true if the given object equals this object" makes no sense to me. I assume the given object, in my case, is 'O'. What is 'this' object referring to?
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Oct 7, 2014
I am new to Java and have read books, the Java docs, and searched the Internet for my problem to no avail. I have an Array of objects that contains strings. How can I get the object's strings to print in a list so that the user can select that object to manipulate its attributes? For example, the user can select "Guitar 1" from a list and manipulate its attributes like tuning it, playing it, etc. I have a class called Instruments and created 10 guitar objects.Here is the code:
Instrument [] guitar = new Instrument[10];
for (int i = 0; i < 10; i++) {
guitar[0] = new Instrument("Guitar 1");
guitar[1] = new Instrument("Guitar 2");
guitar[2] = new Instrument("Guitar 3");
guitar[3] = new Instrument("Guitar 4");
guitar[4] = new Instrument("Guitar 5");
guitar[5] = new Instrument("Guitar 6");
[code]...
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Mar 27, 2015
can a keyevent in java make the space ship and the laser too ?
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Apr 15, 2014
For example I create an object like this:
BankAccount b = new SavingsAccount();
Now lets say that I want to access a method 'addInterest()' that is in the 'SavingsAccount' class I would have to do: '((SavingsAccount)s).addInterest();'
The question I have is why do I have to cast 'b' to SavingsAccount? Isn't the actual object reference of 'b' already an instance of 'SavingsAccount' class? How does the 'BankAccount' affect the object itself? I'm really confused as to what class is truly getting instantiated and how BankAccount and SavingsAccount are both functioning to make the object 'b'.
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Nov 6, 2014
I don't understand why the object reference variable 'a' cannot be recast from a thisA object reference to a thisB object reference.Is it the case that once a reference variable is linked to a particular object type then it cannot switch object types later on.I am facing the Java Associate Developer exam soon and I am just clearing up some issues in my head around object reference variable assignment,
class thisA {}
class thisB extends thisA { String testString = "test";}
public class CastQuestion2 {
public static void main(String[] args) {
thisA a = new thisA();
thisB b = new thisB();
[code]....
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Nov 19, 2014
I am trying to get this to where I can type in a name and it will search through each object and print back the corresponding object info.
Java Code:
import java.util.Scanner;
public class MyPeople {
public static void main(String[] args) {
Person[] p = new Person[] {
new Person("Chris", 26, "Male", "NJ", "Single"),
new Person("JoAnna", 23, "Female", "NJ", "Single"),
new Person("Dana", 24, "Female", "NJ", "Single"),
new Person("Dan", 25, "Male", "NJ", "Single"),
new Person("Mike", 31, "Male", "NJ", "Married") };
[code]....
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Apr 9, 2014
Task:The main method of the class Things below creates an object called printer deriving from the class PrintingClass and uses that object to print text. Your task is to write the PrintingClass class.
Program to complete:
import java.util.Scanner;
public class Things {
public static void main(String args[]) {
String characterString;
Scanner reader = new Scanner(System.in);
PrintingClass printer = new PrintingClass();
System.out.print("Type in the character string for printing: ");
characterString = reader.nextLine();
printer.Print(characterString);
}
}
// Write the missing class here
Note: In this exercise the solution is part of a conversion unit where many classes have been declared. Because of this the classes are not declared as public using the public attribute.
Example output
Type in the character string for printing: John Doe
John Doe
My Class:
class PrintingClass {
public void print(){
System.out.println(characterString);
}
}
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Mar 23, 2015
If I set a Jlist to contain an array of objects, how can I display properties of each object instead of the object array list itself. Ex:
Instead of:
Person1
Person2
Person3
display values such as each person name within the Jlist:
Mike
Paul
Andrew
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Nov 19, 2014
I have just started working with linked lists. I have a linked list of Objects and I want to be able to search for a specific object. But currently my code continues to return false. Also how would I go about removing the first index of the linked list.
public static void main(String[] args) {
LinkedList<Cookies> ml = new LinkedList<>();
int choice = 0;
while (choice >= 0) {
choice = menu();
[Code] ....
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Dec 27, 2014
I am reading Head First: Java and got to Object References. In the book I got a little bit confused on what happens when two object reference's point at the same object so I wrote a small crude test, the below code. This of course clarified what happens but what I am interested in knowing is in what circumstances would you want to have two separate references for the same object when you could just use the original? Eg. v1
class ObjectValue{
int objVal = 1;
}
class ObjectValueTestDrive{
public static void main(String [] args){
// "Value of v# should be" refers to if it copied the given object values, instead of referencing the same object
ObjectValue v1 = new ObjectValue();
System.out.println("Value of v1 should be 1:" + " "+ v1.objVal);
[code]....
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Aug 18, 2014
Explain anonymous objects with example clearly...i read some where anonymous objects advantage is saving memory...it is benificiable when there is only one time object usage in our program..i can't understand one time usage of object ....i know anonymous objects but i don't know in which context we use them in our programs...i did the anonymous object program with my own example but i can't differentiate this one with normal object..i'm providing my own example below
//anonymous object
public class anonymous {
int x=10;
int y=25;
void display()
{
System.out.println("anomymous");
[code]....
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