User Inputting Objects Into ArrayLists
Feb 25, 2014
I'm new to java and up until now whenever I have created an object it has been via the BlueJ interface. I would make an object manually and then manipulate it with my methods.
I have made a basic program which adds objects into arraylists via the BlueJ interface. However I now need to prompt a user to enter a string which should create the specific object and add to its ArrayList.
Is there a way to create objects without manual specifying the parameters? I can provide some of my code if it is needed I am trying to make a crude version of Plant vs Zombies for an assignment.
I am aware of the scanner class but I only know how to prompt a user but I feel like if I can figure a way to create the objects I can dynamically I can associate the string inputs to the proper arraylists.
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Jun 27, 2014
I have to make ask for 2 houses or more (INSTANSED CLASS, with 2 ints ) with the same size(int ), but i they cant use the same door number(int). how do i check in my ArrayList that they have different numbers while not caring about different size? .
The ArrayList is in a class called system. I dont know if i should try to Override the equal or try something else.
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Jan 22, 2015
IDE: BlueJ
I'm creating a small program to count the number of mouse clicks the user is inputting into a BlankArea for a school assignment. I just finished with making the program look nice and all so I was putting in a MouseListener to detect the clicks. However, when I tried adding a MouseListener to the code, the error in the title appeared.
Java Code:
import javax.swing.*;
import java.awt.*;
import javax.swing.border.*;
import java.awt.event.*;
public class CountClick
{
JTextArea textArea = new JTextArea();
[Code] ....
Here's what's going on:
Compiling causes error as described in Title Java Code: createAndShowGUI() mh_sh_highlight_all('java');
cannot be referenced from a static context appears Java Code: public static void main(String [] args) mh_sh_highlight_all('java');
It contains the thread safe and program previously launched without mouse functionality(program appeared when there were no MouseListener components and thread safe had all static method stuff).
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Dec 7, 2014
I have a class with static ArrayLists to hold objects such as Members,Players etc.I want to save the class with the arrays so as to reload them again and hold onto the list of objects within those ArrayLists.
The ArrayClass
import java.io.Serializable;
import java.util.ArrayList;
public class ArrayClass implements Serializable {
[code]....
The arrays within the ArrayClass are empty when i reload the application.I cant tell if the arrays are being properly saved or is it in the reloading from file???
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Mar 9, 2014
I'm writing a java program in eclipse of a tic-tac-toe game. I have to create it using JTextField's only I'm having trouble where the JTextField will only accept one letter and will only accept X and O is there any particular way to do this I started off with this piece of code
String text=tf1.getText();
if(text.length()>1) {
System.out.println("this is not allowed");
tf1.setText("");
But it doesn't work so is there something I'm missing....
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Jan 27, 2015
I am new to the java computer programming world. i am having basic trouble making the statement full and complete. i am trying to get it to say "The speed of the car is <answer> ft/sec" i have tried reading in the my programming book from school but it doesn't tell me how to fix it. the errors I am getting :
cannot find symbol
I have this error twice ....
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Jun 30, 2014
how many types of inputting method in java?can you explain with examples?
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May 6, 2014
Create an application that allows a user to enter values for an array of seven Salesperson objects. Offer the user the choice of displaying the objects in order by either ID number or sales value.
import java.util.*;
public class SalesPersonSort
{
public static void main(String args[]) {
int[] id = new int[7];
int[] salesValue = new int[7];
final int END = 999;
[Code] ....
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Sep 15, 2014
The question states:
>Suppose that aList and bList are instances of java.util.ArrayList. Use two iterators to find and display all the objects that are common to both lists. Do not alter the contents of either list. Write the segment of code assuming that the objects are of type String.
If my understanding is correct, I need to create two Iterators (one for aList and one for bList) to compare both ArrayLists and I should output any value that appears in both lists.
This is my attempt at it:
import java.util.ArrayList;
public class Test {
public static void main(String[] args) {
ArrayList<String> aList = new ArrayList<String>();
ArrayList<String> bList = new ArrayList<String>();
aList.add("One");
aList.add("Two");
[Code] ....
The output:
`One`
`Two`
It stops there. It's clear that my loop is wrong, but I don't really know how to go about fixing it.
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Sep 9, 2014
I have two arraylists. One is personalContactList. The other is businessContactList.
1. I want to take user input that references an object attribute (int),
2. Use it to determine which object is referenced,
3. Find the "type" attribute of that object,
4. Determine which arraylist the object belongs to, based on that type,
5. Use the if else/statement to print out some attributes that depends on which arraylist the object is in.
I believe the code successfully does 1-3, and probably 4. But there is a hangup on 5. I get an indexoutofbounds execption. Which I'm not sure I understand very well.
Here is the code--it's part of a switch statement:
case "c": {
//some code here prints out a list
boolean b = false;
int g;
while (b == false) {
Scanner detailScanner = new Scanner(System.in);
System.out.print("Enter a number to see details: ");
[Code] ....
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Apr 6, 2015
I have two ArrayLists and I want to compare them for common elements, and based on the result I want to update the first Arraylist to only have these elements. sort of like the opposite of RemoveAll() which removes elements in common and keep the ones that are unique. so far I thought of using for loop and .contains() in case it was fault,element not present, remove from list. but I was wondering
in what other ways, perhaps APIs i can use to do that?
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Jan 27, 2014
I have this piece of code, which adds marks into 2 different arrayLists, one for homework marks, and one for examination marks..
ArrayList<Double> homeworkMark = new ArrayList<Double>();
ArrayList<Double> examinationMark = new ArrayList<Double>();
boolean markCheck = true;
do{
//
the purpose of this try catch is to make sure that the entered mark is a valid number. If the program encounters an exception markCheck will become true and the loop will begin again asking the user to enter the marks. If the marks are all encountered correctly markCheck will be false and the loop will end.
try{
for (int i = 1; i <= amountAssignment; i++ ) {
sc.reset();
System.out.print("Homework Mark for Assignment " +(i) + ": ");
homeworkMark.add(sc.nextDouble());
System.out.print("Examination Mark for Assignment " + (i) + ": ");
examinationMark.add(sc.nextDouble());
markCheck = false;
[code]....
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Jul 8, 2014
So I am learning HashMaps/Arraylists and I can't really understand the diamond operator or what it's for. Take the following code for example: Why could we not just do this without the diamond?
Java Code:
import java.util.HashMap;
class Untitled {
public static void main(String[] args) {
HashMap<String, String> map = new HashMap<String, String>();
map.put("California","Sacramento");
map.put("Oregon","Salem");
map.put("Washington","Olympia");
System.out.println(map);
}
} mh_sh_highlight_all('java');
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Apr 15, 2015
So I have a program where you can log in and add/remove friends to and from the friends arraylist. Also I can like a certain thing and that thing will be stored into the likes arraylist. I'm asked to make undo and redo options for whichever action I do.I want to add apple as a friend. After that when I select the undo option, I can undo that action so apple wouldn't be my friend. How I can approach this with a Command Pattern when the input is whatever name or word I inputted to store into the friends arraylist?
I did some research and found that using a command pattern could be my best bet since this has to be done under the Facebook Class I already have. I decided to add parts of what I have ...
In the driver program
Facebook facebook1 = new Facebook();
if (userInput == 6) {
System.out.println("Login");
String operand1 = getOperand("What is the Username? ");
String operand2 = getOperand("What is the Password? ");
System.out.println("Enter a friend to be added. ");
String operand3 = getOperand("What is the Username? ");
facebook1.friend(operand3);
[code]....
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Jun 13, 2014
I have been doing a program that allows the user to input students names and numerical grade values. I have already completed 3/4 of the program but am stuck on the bubblesort method as this is what it requires:
The program must have an indefinite loop, which prompts the user to select a sorting criterion or to end the program, and must also use bubble sort. Note: The user may either select name or grade as the sorting criteria. The program must use bubble sort to sort that data according to the specific criteria and then use another loop to display the data. This process must continue until the user ends the program.
My problem is, while i can easily do the bubblesort, where to look on how to link elements of the two arraylists I'm using (one for grades, one for names) so that when the user decides what sort they want, the individual's name and grade stays together.
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Apr 19, 2015
[URL] I made a program that takes 2 stock values by URL tickers, and now I need it to draw a graph with the values for the 2 stocks, so they can be compared visually. So far my idea was to create 2 arraylists that consist of the values for each stock, so that I can draw the graph so that x always move with 1 step, and y0 is the first coordinate, and y1 is the second, and after that y1 is the first, y2 second etc.
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Feb 22, 2014
I have come across an issue with arraylists. I am writing a text based RPG game as something to start with ...
Initially I had a single zone which was all stored in an arraylist and everything was working in regards to the player moving around. The problem I now have is how to add further zones to my game. Ideally I would like an arraylist for each zone, and would use the below to create each arraylist
public static ArrayList<RoomsClass> castleMap = new ArrayList<>();
The problem I now have is how to handle the player moving, initially with a single zone/arraylist I could reference that arraylist directly
public void findRoomCoords(int ID) {
for (int i = 0; i < castleMap.size(); i++) {
if (castleMap.get(i).roomID.equals(ID)) {
PLAYER.setCurrentRoomZone(castleMap.get(i).roomZone);
PLAYER.setCurrentRoomX(castleMap.get(i).roomX);
PLAYER.setCurrentRoomY(castleMap.get(i).roomY);
PLAYER.setCurrentRoomZ(castleMap.get(i).roomZ);
}
}
}
My initial thought was to use a getter/setter to remove the reference of castleMap from my movement code in order to access different arraylists, however this is where things have fallen over, I can't seem to work out how to get the arraylist name to change, depending on the outcome of the setZoneMap() method.
public void setZoneMap() {
switch (PLAYER.getCurrentRoomZone()) {
case 0: {
zoneMap = Castle.castleMap;
break;
[Code] ....
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Mar 16, 2015
I have an issue with an IndexOutOfBoundsException. I am trying to populate a db from another using arraylists and arrays. I can get the data but the program fails when trying to run the inserts. I am trying to perform SQL in batches of 5. I have added a comment to the failing line.
/*Set in code at beginning*/
ArrayList<String[]> privacyList = new ArrayList<String[]>();
ArrayList<String[]> statementBuffer = new ArrayList<String[]>();
/*Some sql is performed and the following String array is populated*/
while (rs.next()) {
String[] row = new String[55];
resultSetIsEmpty = false;
row[0] = rs.getString("ID");
[Code] ....
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Jul 27, 2014
I am currently working on a project where I need to return data from a database over RMI to a client who requests it. Some of the fields in the Data Object can not be seen by the client so I need to create another object to send over the network instead. The method I use is this...
public static SerializableObject createSerializableObjectFromDataObject(DataObject dataObject){
SerializableObject serializableObject = new SerializableObject();
serializableObject.setField(dataObject.getField());
serializableObject.setAnotherField(dataObject.getAnotherField());
return serializableObject;
}
Is there a better way of doing this? I am creating many subclasses DataObject which all require this static method to be implemented and I can't push it into the superclass because each one needs custom behaviour.
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Jan 23, 2015
how String objects are different from other objects
part 1:
// creating two objects
Dog mydog1 = new Dog();
Dog mydog2 = new Dog();
// comparing the reference variables
if( mydog1 == mydog2){
System.out.println(" The reference variables refer the same object ");
}
else {
System.out.println(" They refer to different objects ");
}
The above code works as I understand objects , it prints "They refer to different objects " to the screen.
Part - 2
// creating two objects ( I beleive, pls correct me if i am wrong )
String a = "haai";
String b = "haai";
if( a == b){
System.out.println(" Reference variables refer to same object");
When i run the above code it prints that a and b refer same object , I don't understand how they refer to same object when i didn't assign " String b = a; ". My question is did java just create one object and stored the same reference values to a and b .
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Feb 24, 2014
import java.util.Scanner;
public class Project_5
{
public static void main (String[] args)
{
Scanner input= new Scanner (System.in);
[code]....
So I'm attempting to have this program take the users input of integers, pressing enter in between each one. If they enter a negative number it lets them know that its invalid. At the end of the program it takes all of the valid integers entered and must add them and average them. I've put the final println in there as a placeholder. If the user types in "6" then presses enter and types in "3" , the output is:
There were 3 valid numbers entered.
The sum of the valid numbers was --- and the average was ---.
There were 0 invalid numbers entered.
It then continues on allowing the user to enter more values. Here is the example output for correct code"
Enter a positive value (EOF to quit): 4
Enter a positive value (EOF to quit): 7
Enter a positive value (EOF to quit): 8
Enter a positive value (EOF to quit): 2
Enter a positive value (EOF to quit): -1
The number "-1" is invalid.
Enter a positive value (EOF to quit): 8
Enter a positive value (EOF to quit): 0
Enter a positive value (EOF to quit): -4
The number "-4" is invalid.
Enter a positive value (EOF to quit): CTRL-D
There were 6 valid numbers entered.
The sum of the valid numbers was 29 and the average was 4.83.
There were 2 invalid numbers.
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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".
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Oct 8, 2014
Basically I need to make a program prompts the user for an integer, check to make sure the length entered by the user is a power of 2 and at least 2. Then I need to convert from base e to base 2 then I need to print the tick marks of a ruler based of the value of the length.
I got the whole converting thing working and the check for a power of 2, that wasn't an issue because it didn't require any recursion. I just don't know how to print out the proper tick mark values.
The way it is supposed to work is that it needs to look like this. Say the user enters 8;
012131210
012345678
Or if the user enters 16;
01213121412131210
01234567890123456
The bottom row is pretty much just the index value, that I print fine.
The top row though is supposed to be the length of the ticks on a ruler, with the middle most value being the value of the conversion from base e to base 2 from above. I can get that printed and what I get just looks like this.
For 8;
000030000
012345678
For 16;
00000000400000000
01234567890123456
As you can see I can get the middle value and the index values below but I don't know how to use recursion to get the right numbers.
Here's my current code.
import java.util.*;
public class TickMarks {
public static void main (String args[]){
Scanner input = new Scanner(System.in);
boolean looping = true;
while(looping == true){
System.out.print("Please enter a length: ");
[Code]...
Now the methods isPowerOfTwo() and printLength() both work fine. However, I'm not sure how to get the left and right side working.
My thoughts were to split the length in half and get a left and right side. I gave both of them arrays so I can keep track of the values. Now as you've seen above I get all zeros and I know it's because that's the default value in an array, I just don't know how to get the proper values.
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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]...
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Mar 3, 2015
I am a first-timer using J2EE and here on coderanch.com and wanted to make a Simple Email-like System which a Registered User can Send Message/Email to another Registered User. how to do it. I have already my register/login process done but I'm stuck on how to make the Email. And I have an sample Bootstrap for my UserInterface which I want to use.
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Sep 29, 2014
I have a requirement to insert the data into xml file . I have used DOM class for doing this. Below is my xml file
<?xml version="1.0" encoding="ISO-8859-1" standalone="no"?>
<deployments>
<applications>
<application>
<name> PCMH</name>
[Code] ....
The thing is if SITA is the name then I have to insert component to the particular envi tabs , if DEVB is the component I have to insert the component there. How can I do this I have done some code its inserting the data at the bottom og the XML .
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