Accepting User Input Of Reference Type
Nov 16, 2014
I have a Homework that's on Polymorphism and inheritance. The problem is of a triangle class. The super class is GeometricObject and the subclass Triangle. I have the parent and child classes compiling, now it's the test program.
The problem is the examples in the book don't show anything about prompting input for objects. The objects in the Triangle class are: side1, side2, and side3 and so I created objects in the test: Triangle sideOne = new Triangle(); . I've tried to compile but jGrasp doesn't like anything I do and the instructor in my class hasn't shown us examples yet. Can I prompt input for reference type and not just primitive type?
View Replies
ADVERTISEMENT
Apr 7, 2014
I have been asked to write a library program that will keep record of books and the year it was published. The program should ask the user how many rows he wants accept the string input from the user and display them in rows and columns. This is how i code it
package multidimension;
import java.util.Scanner;
public class bookrecords {
public static void main(String[]args){
//declaring a scanner variable
Scanner input =new Scanner(System.in);
[code]....
View Replies
View Related
Jan 24, 2015
I don't really know what this means and it is sending an error when I try to run my program I am trying to set the x and y value (Int x and int y) to setVisible false at a specific time in my game but it keeps sending the error that int is not a reference type.
View Replies
View Related
Mar 29, 2014
When I write a statement such as:
myType x;
This means that x is a reference to objects of type, "myType" and no memory has been set aside for an instance of this object. I think it's true that x also has the starting memory address of this object.
What I feel uncertain about is if x is telling the JVM(?) where it can find the starting address of this object, why do we care about the type that x is?
i.e., if we assign x to an object totally unrelated to this type then the compiler would complain - correct? If so, how come, since all x is doing is telling the JVM(?) where to find your object (via the address it contains).
I suppose all, hy a reference has a type associated with it if all the reference does is point you to the object?
View Replies
View Related
Oct 21, 2012
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.
View Replies
View Related
Jul 26, 2014
I have the following code:
public class CollisionManager<T> {
private boolean collision = false;
private T mainEntity;
public <T extends Entities> void handleCollision(T mainEntity, T secondEntity){
this.mainEntity = mainEntity; // This is illegal.
}
}
Why "this.mainEntity = mainEntity" is incorrect and also show me the correct way to achieve this?
The error I am getting is "Type mismatch: cannot convert T to T"
View Replies
View Related
Jan 16, 2015
I am trying to implement the following example to override the equality and hashCode method if the class has reference type member. I do get the expected result "true" for equal and "false" for non-equal objects. But the print statement in the Circle's equal method is not executed when the objects values are not equal. I don't know what i am missing, though i get the equality result "false" as expected for non equal objects.
class Point{
private int x, y;
Point (int x, int y) {
this.x =x;
this.y = y;
[code]....
View Replies
View Related
Aug 14, 2014
class Passenger{
String name;
int age;
char gender;
int weight;
public Passenger(){
[Code] ....
This is showing error.....error it gives isthat it cannot change from string type to passenger type......... How to do it??????
View Replies
View Related
Apr 17, 2014
public class {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
double[] numbers = new double[10];
System.out.println("Enter " + numbers.length + "numbers");
for (int i = 0; i < numbers.length; i++) {
numbers[i] = input.nextDouble();
[Code] .....
I am trying to reference the input "numbers[i]" to my mean method, how do i do that?
View Replies
View Related
Mar 26, 2015
This is my code inside the method:
@Post
public static String getDetails(Representation entity) throws Exception {
String customerId = getQuery().getValues("cus_id");
}
I use this code in Restlet Representation. I try to get the value from the Request API. But I am facing the problem as "Cannot make a static reference to the non-static method getQuery() from the type Resource".
View Replies
View Related
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'.
View Replies
View Related
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]....
View Replies
View Related
Apr 27, 2014
I am writing the following program in Java SE 7. It throwing "Cannot make a static reference to the non-static type String" . However if I write parameterised String inside main method as java.lang.String[] args, it compiles fine.
class MainClass<String> {
<T> MainClass(T t) {
System.out.println(t.getClass().getName());
}
public static void main(String[] args) {
System.out.println("asdasd");
new MainClass<>("");
}
}
I mean following programs compile fine in Java SE 7 :
class MainClass<String> {
<T> MainClass(T t) {
System.out.println(t.getClass().getName());
}
public static void main(java.lang.String[] args) {
System.out.println("asdasd");
new MainClass<>("");
}
}
View Replies
View Related
Jan 25, 2014
I had to use scanner to receive input from the user for a formula and everything compiled and worked correctly except when I entered a double into the Scanner, it only accepts ints and gives me this error every time I enter a double:
java.util.InputMismatchException
at java.util.Scanner.throwFor(Unknown Source)
at java.util.Scanner.next(Unknown Source)
at java.util.Scanner.nextDouble(Unknown Source)
at TestA1Q2.main(TestA1Q2.java:36)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at edu.rice.cs.drjava.model.compiler.JavacCompiler.runCommand(JavacCompiler.java:272)
I know that you usually get that error when the Scanner expects something else that is different from what you type and I have looked over my code time and time again and cannot find anything. I created a test program to see if it was just that problem and not something else in the code and I still got the same error but when I tried compiling and running it here browxy.com everything worked and I got the right answer for the formula. Here's the test I used:
import java.util.Scanner;
public class TestA1Q2 {
public static void main(String[] args) {
Scanner keyboard = new Scanner(System.in);
System.out.println("Enter a double");
double velocity = keyboard.nextDouble();
}
}
At this point I'm thinking it might be a problem with my install of DrJava and I've tried re-installing but nothing changed.
View Replies
View Related
Apr 9, 2014
Write a java program that will ask a user to input grades until the user inputs the sentinel value -1. The program should test each input to determine whether 0<=grade<=100. If the grade entered is within this range, the program should print "Grade accepted;" if not, the program should print "Invalid input".
View Replies
View Related
Nov 4, 2014
I have been struggling with this program for weeks. This program is supposed to take a user's inputted odd number and then print out all prime numbers lower than that number.
public class PrimeNumber
{
Scanner scan = new Scanner(System.in);
int userNum;
String neg;
public void getUserNum()
[code]...
View Replies
View Related
Apr 9, 2015
Where do I input this segment?
Scanner user_input = new Scanner( System.in );// This line goes at the top with the other global variables
public void getUserInput(){
System.out.print("Enter litres: ");
litres = user_input.nextDouble( );
System.out.print("Enter mileage: ");
mileage = user_input.nextDouble( );
System.out.print("Enter speed: ");
speed = user_input.nextDouble( );
[Code] ....
This is my client file.
class Client{
public static void main(String []args){
Bike R1=new Bike(5.0, 60.0,30.0);//create bike object with params
Bike R2=new Bike();//without params
System.out.println(R1.increaseSpeed());//calling methods
System.out.println(R1.maxDistance());
System.out.println(R2.increaseSpeed());
System.out.println(R2.maxDistance());
}
}
View Replies
View Related
Apr 26, 2015
I can't figure out what this error message "Cannot make a static reference to the non-static method getEndUserCharge(long, long, long, long) from the type UpdateUserWS" actually means.
The error is coming from:
public void updateDetailsPackage() {
some unrelated code
long zero=0;
double endUserCharge=0;
endUserCharge = UpdateUserWS.getEndUserCharge(long zero, long zero, long zero, long zero); <-------- error is here
[Code] ....
View Replies
View Related
Mar 10, 2015
I am trying to get through JSF /PF tag for h:inputSecret but its not taking or displaying value. Please see the code snippet below
demo.xhtml
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml"
xmlns:h="http://java.sun.com/jsf/html"
[code]....
I am using JSF 2.2.
View Replies
View Related
Sep 23, 2014
I don't understand how i'm supposed to define a variable when the user has to type it into the program so it can be converted. This program i'm working on is supposed to convert from meters to feet (meter = feet * 0.305) but the user has to type in the meters they want converted. how do i solve the problem that keeps coming up that says "variable meter symbol cant be found" ? I keep trying different lines to no avail
public class Lab2
{
public static void main(String[] args) {
double feet = meter * 0.305;
double meter = feet/0.305;
System.out.println("Enter in feet for conversion to meters");
meter = meter * 0.305;
[Code] .....
View Replies
View Related
May 21, 2014
Ok, so I have to make a program that tells the user to type a sentence and at the end of the sentence a "." must be put to end the program. If a "." period is not entered, it must re-prompt the user to enter a period. On top of all this, the program has to count the number of letters in the sentence. I cant seem to get the while loop working and I cant find anywhere how to make a counter count the number of letters.
import java.io.*;
class Sentence
//The purpose of this program is to
[Code]....
View Replies
View Related
Nov 13, 2014
I have been coding in my class at school (Grade 11 Computer science) and i just downloaded the program on my computer at home, unfortunately i cannot access my computer notes at home and i also dont remember certian specifics of coding, so my question is how would i get user input to create a program. The comments are the parts i dont remember. (I am trying to slowly build my memory with this stuff)
Here is my code so far:
import java.util;
[highlight=java]
public class hello_world {
public static void main(String[] args) {
string name;
//WHAT DO I PUT HERE????
[code]....
View Replies
View Related
Apr 19, 2014
I'm working on creating a dice game and getting the users input is giving me a really hard time. I have the main game working but this part I'm stuck on. The problem is that it's not giving me the chance to enter the second input when I ask for the game.
//Create Scanner object
Scanner keys = new Scanner(System.in);
//Get chips
[Code]....
*****This is what I get when I run it
run:
How much money would you like to change? 50
You now have $50 in chips.
What game do you want to play? You did not pick dice.
View Replies
View Related
Oct 11, 2014
Is there a way you can control user input?
For example, is it possible to only allow the user to enter digits?
View Replies
View Related
Feb 4, 2014
I have been given a piece of work to do for College that requires me to format user input. For example: This is an example of text that will have straight left and right margins after formatting
will transform into:
This..is..an.example
of..text..that..will
have..straight..left
and...right..margins
after.....formatting
The user inputs the width, in the case above being 20. Each line has to therefore be 20 characters long. All spaces are to be replaced with full stops.
This.is.an.example.o
f.text.that.will.hav
e.straight.left.and.
right.margins.after.
formatting..........
public class Main {
public static void main ( String args[])
[code]....
View Replies
View Related
Jul 2, 2014
Goal is to get user input and sum together. I've tried it different ways. This is the one with the least amount of problems.
Exception in thread "main" java.lang.RuntimeException: Uncompilable source code - Erroneous sym type: java.lang.Integer.parseInt
ArrayList<Integer> leftCU = new ArrayList<>(); {
System.out.println
("Please enter one at a time the number of CU's for each class that is left to complete. Enter Q when done.");
leftCU.add(in.nextInt());
[Code] .....
View Replies
View Related
