Non-Parameter Constructor Calls Two Parameter Constructor

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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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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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 30, 2014

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I know that if you put something like ?x=1 and then getParameter("x") on the servlet page would work, but then all the IDs would have the same parameters since I'm using a for loop to print out my ArrayList of objects.

My code for the jsp part is below.

for (int count=0; count<list.size(); count++) {
%>
<tr>
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[Code] ....

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Apr 30, 2014

I'm using Java in BlueJ where I'm trying to write a class to store cycling club membership details in a map. I'm trying to pass a map as a parameter to a function that will iterate over the map and print out the member details. My code is:

public class CtcMembers
{
//instance variables
private Map<String, Set<String>> memberMap;
/**
* Constructor for objects of class CtcMembers

[Code] ....

When I execute the following in the OU workspace:

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c.addCyclists();

I can see a map populated with the expected details.

When I execute the following in the OU workspace:

c.printMap(c.getMap());

I get the following error:

java.lang.ClassCastException: java.util.HashSet cannot be cast to java.lang.String
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in (OUWorkspace:1)

I wasn't aware I was trying to cast anything so this has got me baffled.

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May 18, 2014

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Here is the code:

package javaapplication5;
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{

[Code].....

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JSP File

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in the java file I am setting a parameter to session

request.getSession().setAttribute("replaceVal", "Value headline");

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The replacement should happen on an event.

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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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Mar 23, 2014

Is it possible to pass column name as a parameter using servlets?

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String sql="alter table cs1_cn add " +date+ " boolean";
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Mar 25, 2015

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Java Code:

public ArrayList <Customer> getMailingList(String keyword){
ArrayList <Customer> key = new ArrayList<Customer>();
keyword = keyword.toLowerCase();
for(Customer c : data){
if(c.getState().contains(keyword) || c.getCity().contains(keyword)){
key.add(c);
}
}
return key;
} mh_sh_highlight_all('java');

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How to write a new file:

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import java.io.*;
import java.io.PrintWriter.*;
import acm.util.*;
import javax.swing.*;
public class PrintWriter extends ConsoleProgram {

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try {
PrintWriter wr = new PrintWriter( new FileWriter ("hello.txt") ) ;
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wr.close();
} catch (IOException er) {
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}
}
}

(I added the imports at top myself.) However, I am getting compiler errors for the lines: PrintWriter wr = new PrintWriter( new FileWriter ("hello.txt") ) , which says that the constructor PrintWriter( FileWriter ) is undefined, and
wr.close();, which says close() method is undefined.

Pretty sure the only real problem is that PrintWriter is not accepting the FileWriter as constructor, but I don't see why. I have tried this on machine with JRE 1.4 and it worked as expected, creating new file titled "hello.txt", prints line of "Hello world!" in that file, and saves it to the directory I picked in the dialog. But I can't get it to work on this machine that uses Compiler 1.6, Java Runtime v8u25.

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public void invia(OiStorto invioaca) throws Exception {      
         Long id=0L;
        try {
               //some code
     for (VElenpere elenpere : elenperes) {

[Code] ...

The method called in the for:

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[Code] ....
   
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try {
//some code
} catch (NullPointerException e) {
            e.printStackTrace();
            //return id;
        }
       
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I use :

ResultSet rs = null;
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<img >
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Now this is JSP page content

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Mar 6, 2014

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[code]....

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I want to populate the array pergunta in a previous class and use in this one.

import javafx.application.Application;
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Java Code:

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......
} mh_sh_highlight_all('java');
{

So, how does Scanner calculates a passed String? I just want to know the way it calculates/reads.

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