Why Parameter Types Declared With Final Modifier

Jan 7, 2014

I have come across some code where the method signature is like,

public methodName(final String argument) {
...
}

I fail to grasp why final is needed here. Is it only because of the field immutabilty? What big picture am I missing in this case?

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Declaring Static Int - Illegal Modifier For Parameter

Feb 15, 2014

I accidentally wrote a code differently than what I should've, and I got these errors :

"Illegal modifier for parameter a; only final is permitted"
"Illegal modifier for parameter b; only final is permitted"
"Illegal modifier for parameter c; only final is permitted"

The code that I wrote and gave these errors:

Java Code:

class Math {
public static void main(String[] args) {
static int a = 11;
static int b = 35;
static int c = 29;
//the rest of the code below

[Code] ....

I noticed that I can declare "static int" only under "class Math" and not under "public static void main".(I had to remove "static" if declaring int under "public static void main");

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Creating Final Arrays With Final Elements

Aug 2, 2013

I want to create a final array with final elements
 
{code}
final int[] array = {0, 1, 2, 3, 4, 5};
{code}
 
But here only the reference of the array is final , not it's elements ... So how can I do that??

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Default Access Modifier

Mar 21, 2014

class Course
{
String courseName;
}
class Entry
{
public static void main(String[] args)
{
Course c = new Course();
c.courseName="java";
System.out.println(c.courseName);
}
}

I have defined these two classes under same java project in Eclipse IDE with no package. Above two class are having default classes. class Course is also having a instance variable courseName with default access. So when we try to compile the Entry class it will give the errors while accessing the instance variable courseName on Line 6 and 7. As both the classes are having default access modifier. class Course is not visible to class Entry, then why we do not get any compilation error while creating the object of class Course on line 5?

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Cannot Access Field Even Though It Is Declared As Private?

Jul 9, 2014

I think the following code should trigger a compiler error.

public final class IPoint3D {
private double x;
private double y;
private double z;
public IPoint3D(double x, double y, double z)

[Code] .....

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Servlets :: Session Attribute Keeps Reverting To Declared Value

Dec 29, 2014

Being new to java I am a bit lost as to why my session attribute for this banking app wont add the deposits to the session var... it just keeps going back to the amount I set it to originally - so if I set the beginning balance to 3000 then deposit 100 it becomes 3100, but if I then try deposit another amount eg. a extra 200 it becomes 3200 not 3300 like it should be !!

import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
import java.util.*;
import java.net.*;
import java.text.DecimalFormat;
public class SessionBank extends HttpServlet

[Code] .....

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Unreported Exception - Must Be Caught Or Declared To Be Thrown

Oct 4, 2014

I am getting the above error and am not sure which direction to proceed. In the class, the only way we have discussed getting user input is by System.in.read. I have searched and apparently found better methods for getting user input, but wanted to stick with what has been presented thus far.

Assignment Directions:

1. Create a new class named “valuemethod”

2. Create a new method named “Main”

3. In Main Write the code that will call the method EnterPay and YearlySal

4. Create a new method named “EnterPay”

5. In the EnterPay method Write the code that asks the user to input their hourly wage. Use the formula to calculate their yearly salary: wage * 2040. Return the yearly salary to the main method

6. In the main method write the code that will display this: “Your yearly salary is:

Java Code:

package valuemethod;
public class Valuemethod
{
public static void main(String[] args)
//throws java.io.IOException -- moved to EnterPay

[Code] .....

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Instance Variables Can Be Declared In Class Level Before Or After Use

Jun 3, 2014

From the tutorial:instance variables can be declared in class level before or after use.But the code below does not compile. Why?

Java Code:

public class MainApp {
i=5;
public static void main(String[] args) {
System.out.println("Hello World");
}
int i;
} mh_sh_highlight_all('java');

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Method Implementation Declaring Exception Other Than That Declared In Interface

Aug 31, 2014

The 2 minute drill from page 69 SCJP kathy and bert book, says regarding Interfaces, that - "A legal nonabstract implementing class must not declare any new checked exceptions for an implementation method."

When I try the below given code in eclipse , it does not throw any errors . (Here I have tried to throw NullPointerException from testFunc whereas the interface function throws IllegalStateExc)

package abstracttesting;
public class StaticCheck implements check{
public void testFunc() throws NullPointerException{
// TODO Auto-generated method stub
} public static void main(String[] args) {
// TODO Auto-generated method stub
}
}
interface check{
void testFunc() throws IllegalStateException;
}

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Preferential Treatment To Order In Which Variables Are Declared In Java

Jun 25, 2014

public class Ball {
private int a=show();
int b;
Ball()
{
b=20;
}
public static void main(String args[])throws Exception {
System.out.println(new Ball().a);
}
private int show()
{System.out.println(b);
return b;
}
}

I wanted to know when are the objects created ? when are they initialized? and how is show() getting called without any reference or "this" ?

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Why Super Classes Always Declared As Interfaces And Not Abstract Class

Dec 1, 2014

While reading the design patter book, i got one doubt ,There is a List an interface having sub classes ArrayList, LinkedList etc.,

Q1) My question is Why they declared the List as interface rather than Abstract class?

Q2) i read some site -

List l = new ArrayList(); Why it is GOOD line?
ArrayList l = new ArrayList() ; Why it is BAD line?

Answer required with detailed information for Q1 and Q2.

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Method Is Declared To Take Three Arguments - Only Two Arguments Pass On Program Call

Jun 9, 2014

A method is declared to take three arguments. A program calls this method and passes only two arguments.Will it take the third argument as

1 null
2 void
3 zero
4 Compilation error

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Why Constructor Cannot Be Final

Oct 27, 2014

"A constructor cannot be abstract, static, final, native, or synchronized."

I understand on why it can't be all of the above, except "final".

Why can't we have a final constructor, i understand constructors are not inherited, hence no chance/case of overriding etc. But why is it not allowed at all ?

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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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Final And Static Method?

Feb 7, 2014

My teacher has asked me one question that "What is difference between the final method and static method".

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Why Are Final And Abstract Called As Modifiers

Feb 8, 2015

I just wanted to know that why are final and abstract called as modifiers ,what is the essence of calling them as modifiers since there are two types of modifiers access modifiers and non-access modifiers so final and abstract come under the second category ,so why are these called as modifiers?

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Final Reference Variables In Java

Feb 28, 2015

I am unable to understand the meaning of this sentence "final reference variables must be initialized before the constructor completes.",What is trying to imply?

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When Final Variable Occupy Memory

Sep 23, 2014

when final variable occupy memory in java?

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Final Static Variables In GregorianCalendar

Oct 27, 2014

why using the get method(c.get(c.HOUR_OF_DAY)); gives me the correct hour(currently 19) but directly accesing c.HOUR_OF_DAY returns 11 ? It shows In the documentation that HOUR_OF_DAY is public.

import java.util.*;
public class calendar2 {
public static void main(String[] args) {
new calendar2().timer();
}
private void timer() {
Calendar c=Calendar.getInstance();
//c.clear();
System.out.println(c.get(c.HOUR_OF_DAY));
System.out.println(c.HOUR_OF_DAY);

}
}

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How To Take Runtime Value For Static Final Variable

Jul 28, 2014

How can i take run time value for static final variable...my lecturer said first time assignment is possible for declared final variable but in my case it shows compile time error..I'm placing my program below with error message

class Sample
{
static final String cname;
void print() {
System.out.println(cname);
}
public static void main(String args[])
{
cname=args[0];
Sample s=new Sample();
s.print();
}
}

Sample.java:11: cannot assign a value to final variable cname.
cname=args[0];

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Grade Input And Final Average

Sep 15, 2014

For this assignment you will be writing a grade book program. The program will work for one student. It will need to take as input the students name. The user will then be asked to input grades into three categories in this order:

1) homework;
2) quizzes;
3) tests.

The grades in a given category will be averaged to one number that is the average of all grades in that category. The final average will be the weighted average of each category, where homework is worth 25% quizzes are worth 25%, and test are worth 50%. Like this:

Homework Grades: 65, 70, 75, 80, 80 Homework Average: 74
Quiz Grades: 75, 80, 85, 80. Quiz Average: 80
Test Grades: 75, 80, 85, 75 Test Average: 78.75
Final Average = 0.25*HomeworkAvg + 0.25*QuizAvg + 0.50*TestAvg = 77.87

But i only have the average and i dont know how to move past that..

Heres my average code :

import java.util.Scanner;
public class Homework3 {
public static void main(String[] args) {
Scanner myScanner = new Scanner(System.in);
int gradeCount = 0;
int grades = 0;
int holder = 0;

[Code] .....

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What Is The Impact Of Declaring A Method As Final

Nov 14, 2014

1 Can method declared as final be overridden and overloading ?

2 if A is static sub class of B. how to access a method in class A ?

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Parsing Error With Final Bracket

May 8, 2014

Im working on a class to add to my final project but im getting a parsing error for the final bracket, i double checked to make sure im not missing any but im still getting an error

import java.util.Scanner;
public class totalprice
{
public static void main(String[] args)
{
scanner keyboard = new Scanner(System.in);
{
DecimalFormat num = new DecimalFormat("#.00");
char meal;
int ammount;
double cost;

[code]....

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Where Are All Keywords Like Final And This Stored In Java

Jan 23, 2014

Which package or class i can find all the predefined keywords in java like "this" etc...

actually i want to know if this operator is itself final in nature or not from its syntax?

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Accessing Variables - What Is The Final Value Of Counter

Mar 7, 2015

While reading head first java i encountered a problem(Pg. 90 chapter 4 - mixed messages).

Suppose in a class(say A) outside main() a counter variable is declared and initialized to 0.

In main() declared the array of objects of the class A.

Consider a while loop in which we increment the counter as follows:

public class A{
int counter = 0;
public static void main(String[] args){
A[] arr = new A[20];
int x = 0;
while(x<4){
arr[x] = new A(); //arr[] is array object
arr[x].counter += 1;
x++;
}
}
};

what is the final value of counter ? will it be the same for all array objects.

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Final Field Initialization With Exceptions

May 11, 2014

consider:
 
class A {
     final Object b;
     public A(C c) {
          try {
               b = c.someMethodThatMayThrowSomeException();
          } catch (SomeException e) {
               b = null; // This line results in compiler error: "variable b might already have been assigned"
          }
     } // take away b=null line and you get "variable b might not have been initialized" on this line
}
 
Why? How could 'b' be assigned if the exception was thrown?
 
Btw, the workaround is to wrap the method call:
 
private final Object initB() {
     try {
          return c.someMethodThatMayThrowSomeException();
     } catch (SomeException e) {
          return null;
     }
}
 
and use b = initB(); in the constructor.  But that seems like it should be unnecessary.

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