Are Terms Local Variable And Member Variable Comparable
Oct 27, 2014
The term "Local variable" is related to scope. That is a local variable is one which is defined in a certain block of code, and its scope is confined inside that block of code.And a "Member variable" is simple an instance variable.
I read in a discussion forum that when local variables are declared (example code below), their name reservation takes place in memory but they are not automatically initialized to anything. On the other hand, when member variables are declared, they are automatically initialized to null by default.
Java Code: public void myFunction () {
int [] myInt; // A local, member variable (because "static" keyword is not there) declared
} mh_sh_highlight_all('java');
So it seems that they are comparing local variables and member variables. While I think a member variable can also be be local in a block of code, isn't it?
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May 23, 2015
Java Code:
public class MountainBike extends Bicycle {
// the MountainBike subclass has
// one field
public int seatHeight;
// the MountainBike subclass has
// one constructor
public MountainBike(int startHeight, int startCadence,
[Code] ....
At first,
Java Code: public int seatHeight; mh_sh_highlight_all('java');
tells us that seatHeight is NOT a static field (because of the absence of static keyword).
Whereas in the constructor, the absence of dot notation (like something like this.seatHeight) in
Java Code: seatHeight = newValue; mh_sh_highlight_all('java');
shows that it IS a non-member/static variable.
How does this make sense?
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Mar 9, 2014
I have a Tcr object as a member variable of the JFrame. But When ChangeListener swings into action, the variable inside it are all nulls. the TcrPanel is created before the ChangeListener is triggered.
Tcr tcrPanel;
tabbedPane.addChangeListener(new ChangeListener() {
@Override
public void stateChanged(ChangeEvent e) {
if (e.getSource() instanceof JTabbedPane) {
CloseButtonTabbedPane pane = (CloseButtonTabbedPane) e.getSource();
[Code] ....
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Jun 19, 2014
I am reading input from a file that has following information:
line 1 = numbers of integers in array,
line 2 = elements in array1,
line 3 = elements in array2.
These lines constitute a test case. There are 1000 test cases in the input file.
So basically, I read the length of arrays, populate the arrays by reading from the file.
The code is below ( I have not included reading input code):
while(test_case<1000){
if (count == 1){ //count keeps track of lines in input file
vec_length = Integer.parseInt (tokenizer.nextToken());
count++;
continue;
}
if (count == 2){ //populates array1
vector1 = new int[vec_length];
for (int i = 0; i < vector1.length; i++)
vector1[i] = Integer.parseInt (tokenizer.nextToken());
count++;
continue;
}
Array2 is populated using the same as above code. However when I use the following code:
for (int i=0; i<vec_length; i++)
temp += vector1[i]*vector2[i];
I get " local variable vector1 and vector2 have not been initialized error". But both arrays have been initialized in the if{} block. Is it because initialization was local to if block?
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May 12, 2015
As a studyproject I'm currently writing a class the allows me to get al fun dates (like when eastern is in a given year, what day a given date has, calculate the date of tomorrow).
While working on the following method:
public String getNextDate (int day, int month, int year) {
String nextDate;
int nextDay = getNextDay(day, month, year);
int nextMonth = getNextMonth (day, month, year);
int nextYear = getNextYear (day, month, year);
return nextDate = "the day after " + month +"-" + day + "-" + year + " is " +
nextMonth + "-" + nextDay + "-" + nextYear + ".";
}
I get a notion in my lovely IDE (eclipse) reminding me I'm not using nextDate ("The value of the local variable nextDate is not used"). But I feel I really do use nextDay here. So either I'm making a coding(style) mistake giving me this notion or I should just ignore this notion.
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Feb 3, 2014
Here, I have just tried out to take a value from the database and storing it into local variable then I want to have that value in the value attribute of <input> tag but somehow, I can't get it..
Here, below is my code..
<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
pageEncoding="ISO-8859-1"%>
<%@ page import="java.sql.*" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "[URL]....">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
[Code]...
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May 13, 2014
public class Apples{
public static void main (String args[]){
int array[]={21,16,86,21,3};
int sum=0;
int average;
[Code] .....
Eclipse: Exception in thread "main" java.lang.Error: Unresolved compilation problem:
The local variable average may not have been initialized
at Apples.main(Apples.java:11)
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Sep 30, 2014
I have a question regarding best practice in using local variables as my method return variable. I have a method like this:
myReturnObject getMyObject(String input) {
myReturnObject myObject = null;
try {
myObject = helperObject.someOtherMethod().getObject(input); //getObject has return type myReturnObject
} catch (Exception e) {
//log any problems
}
return myObject;
}
And I'm wondering if I rewrite like this if I'll see some performance optimization benefit:
myReturnObject getMyObject(String input) {
try {
return helperObject.someOtherMethod().getObject(input); //getObject has return type myReturnObject
} catch (Exception e) {
//log any problems
}
return null;
}
myObject can be quite large -- so I'm wondering if I can omit the myReturnObject local variable instance if it'll save some work from the garbage collector.
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May 21, 2014
Given the case I have an object which is assigned only once. What is the difference in doing:
public class MyClass {
private MyObj obj = new MyObj("Hello world");
private MyClass(){}
//...
}
and
public class MyClass {
private MyObj obj;
private MyClass(){
obj = new MyObj("Hello world");
}
//...
}
Is there a difference in performance or usability? (Given also the case there are no static calls expected) ....
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Jan 11, 2015
Given a reference variable : Car c1 = new Car();
when we create another variable and set it equal to the first : Car c2 = c1;
we're pointing c2 at the same car object that c1 points to (as opposed to pointing c2 at c1, which in turn points at the car). So if we have code like,
Car c1 = new Car();
Car[] cA = {c1, c1, c1, c1};
are we doing the same? Are we creating four *new* reference variables, each of which points at the same car (again as opposed to pointing them at c1 itself)? I think so, but want to make sure I'm understanding this correctly.
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May 23, 2014
I have a JFrame jf and JPanel jp on it. jp has five TextFields named cel1, cel2.. cel5. I wish to construct a String Cel + for loop index and run a for loop to reset the values of all the text fields using a single statement such as cel1.SetText("abc"). Similar things can be done in foxfro. How does one do it in java?
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Feb 17, 2014
How do I use a variable in an if statement to return a public void method from another class? I've tried:
System.out.print("select 1 - 6: ");
Scanner myScanner = new Scanner(System.in);
myScanner.nextInt();
if (myScanner.nextInt()==1) {
carSelection colour = new carSelection();
colour.carSelection();
The method colour in class car selection is just 4 print line statements? I've // out the if statement to see if it is correctly calling the method and displaying the data and it is?
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Oct 6, 2014
What is variable shadowing?When does it occur?
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Feb 7, 2014
Regarding the code examples in Head First Java, this is from Chapter 5, regarding the beginning creation of the dot com game. There are two classes in quesiton
the first is the SimpleDotComTester class:
public class SimpleDotComTester {
public static void main(String[] args)
{
SimpleDotCom dot = new SimpleDotCom();
int[] locations = {2, 3, 4};
dot.setLocationCells(locations);
String userGuess = "2";
String result = dot.checkYourself(userGuess);
}
}
and the second one is the code for the checkYourself () method in the SimpleDotCom class
public class SimpleDotCom {
int[] locationCells;
int numOfHits = 0;
public void setLocationCells(int[] locs)
[code]....
Now I noticed that both classes use a variable called result; the program runs fine, but assume from the example that you can use the same variable name two different classes;
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Mar 16, 2014
i have a datatable with id= tblId#{emp.id}
<c:set var="tableID" value="tblId#{emp.id}">
displaying employee details inside c:forEach
closing dataTable.
[code]...
For ex.Displaying 5 table dynamically.Need to validate check box selected or not.5 table are displayed.But it shows 5th table row id only.It is because of local varible declaration?
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Nov 6, 2014
I'm making a program where the user enters an ID number and can submit the amount of sales that person made for a specific product and write to a file. One of the things I have to do is making a running sum of the sales for each product for all people combined as well as an accumulation of the a persons sales every time he enters data. Everything seems to be working execpt my values like person1Total, person2Total...etx and product2Total.
When I try to write them to the file, they always come out at 0.0 even though they should be the sum of the indexes of the array sales.
import java.io.*;
import java.util.Scanner;
public class SalesReport {
// private static double p1Total, p2Total, p3Total, p4Total;
private static double product1Total, product2Total, product3Total, product4Total, product5Total;
private static double person1Total, person2Total, person3Total, person4Total;
public static void main(String[] args) throws IOException
[code]....
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May 2, 2015
I'm working on a program where the user inputs song information (name, artist, filesize, duration) which is stored in a database. Once the user adds a song, the details should be stored in the first empty song slot (4 song slots total) and then taken back to the menu interface.
What I'm having trouble with is that I can add the first song fine (song1), but when I try to add another song, the information entered into song1 is gone. I've worked out that this is because every time I call upon the addNewSong() method, I'm creating four Song objects that are brand new with the line:
Song song1 = new Song();
Song song2 = new Song();
Song song3 = new Song();
Song song4 = new Song();
How to fix this problem is where I'm stuck because if I move these lines elsewhere, I get a 'cannot find symbol - variable song1' error.
Here is my code:
public class SongDatabase {
Scanner console = new Scanner(System.in);
public void addNewSong() {
Song song1 = new Song();
Song song2 = new Song();
Song song3 = new Song();
Song song4 = new Song();
if (song1.isEmpty()) {
[code]....
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Jul 18, 2014
I trying to display the value of a variable from a method, but I don't know why it will I can't do it.
//Java extension package
import javax.swing.JOptionPane;
public class Palindrome
{
public static void main(String[] args) {
int number = 0;
int palindrome = 0;
[Code] ....
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Oct 24, 2014
I have code that displays 3 game scores the series total and average. For some reason game 3 outputs 0 and game 1 and 2 output correctly. I don't see anything different that game 3 is doing that game 1 and game 2 aren't so I'm not sure what the problem is.
java file
package com.valenciaprogrammers.mybowlingscores;
import java.text.DateFormat;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Date;
public class BowlingScores implements Comparable<BowlingScores>{
private long id;
[Code] .....
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Apr 17, 2014
How can I make variable from table value? Example:
Java Code:
String table [] = {"vara","varb"};
for(int i = 0; i < table.length; i++)
{
int table[i] = i;
} mh_sh_highlight_all('java');
And vara = 0, varb = 1 here.
Is this even possible?
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Apr 23, 2014
i'm new withh java netbeans, and i want to make program where variable from database. how to get value from database to use in variable/
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Apr 30, 2014
I have a problem with my code. When, on strausParser class, i create the new object Beam i give him an array of Node object called "nodiestremi".
The problem is that when a Beam is created, the Beam created before take the Node of new Beam. Why it appends?
public class Main {
public static void main(String[] args) throws NumberFormatException, IOException{
SetFile.setupWindows();
Structure structure = new Structure();
}
public class SetFile {
}
I get an output like this:
Import node complete
0 0 0 1
0 1 1 2
0 1 1 0
0 2 2 4
Import beam complete
and not like this:
Import node complete
0 0 0 1
0 0 1 2
0 0 1 0
0 0 2 4
Import beam complete
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Oct 3, 2014
My code has a method where the users input a bunch of variables and then those variables get added together in a new variable. What I want to know is how do I call the variable that is in the other method to another method?
import java.util.*;
public class Calc{
public static void main (String [] args){
determinevalue1();
determinevalue2();
determineTotalvalue(double value1, double value2);
[Code] ....
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Dec 8, 2014
I have a class Tree in which all the methods to build a tree are in place. But however I would want variable of by Tree which is pointing to the last node being added to the tree.
So basically every time you keep adding a node to the tree you tail pointer gets updated to point to the last node. I have this so far.
public class NonEmptyTree implements Tree {
private Tree left;
private int data;
private int leftleafCount;
private int rightleafCount;
private Tree right;
private Tree tail; // This variable must be shared by all the object. There needs to just one tail pointer to the tree.
public Tree insert( data ) {
tail = // gets updated every time when new node gets added.
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Dec 27, 2014
I am going through Thinking in Java, 4th Ed and I came across the section that talks about overloading variable arguments. I tried out a piece of code from the book. (Method and class names not exactly the same).
public class Varargs
{
public static void m1(Character... args)
{
System.out.println("Character");
[code]....
In the above code, the compiler throws an 'Ambiguous for the type varargs' error. The error goes away if the first method is changed to:
public static void m1(char c, Character... args)
why there is ambiguity in the first piece of code and not the second.
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Mar 3, 2014
My objective is to write a program that calculates the bodyfat of people. The difficult thing is, that the calculations are different for males and females, so I tried to prompt the user to state whether they are male or female, then use and "if" statement to tether their response to the corresponding calculations.
Here's my algorithm:
Here's what I have:
package bodyweight;
import java.util.Scanner;
public class Weightcalc {
static Scanner console = new Scanner(System.in);
public static void main(String[] args){
[Code] ....
It keeps telling me that bodyweight is not initialized, but when I do, I get a hell of a lot more bugs on everything telling me they aren't initialized. I just want the program to transfer the user to select inputs, based on whether they are male or female.
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