Java

Re: How to calculating Business Hours in java

22-Sep-11 22:57

jschell wrote:
5. Go to 2.

Go to? You used a 'king go to! Back of the class and write out 100 times "Using GO TO is neither big nor clever and I will not do it again." Mad | :mad:

Panic, Chaos, Destruction. My work here is done.
Drink. Get drunk. Fall over - P O'H
OK, I will win to day or my name isn't Ethel Crudacre! - DD Ethel Crudacre
I cannot live by bread alone. Bacon and ketchup are needed as well. - Trollslayer
Have a bit more patience with newbies. Of course some of them act dumb - they're often *students*, for heaven's sake - Terry Pratchett

jschell23-Sep-11 12:19

jschell

23-Sep-11 12:19

I also used the English language.

Perhaps you were confusing it with a programming language.

Re: How to calculating Business Hours in java

TorstenH.24-Sep-11 7:53

Re: Javascript in livecycle

24-Sep-11 7:53

that was probably a homage to the old days when we all played with our C64's.

regards Torsten
I never finish anyth...

Javascript in livecycle

Incognito121-Sep-11 4:20

Incognito1

21-Sep-11 4:20

How do I add a javascript to an adobe livecycle form that will give me an enlarrged pop up image as I hover the mouse over an image.

Nagy Vilmos21-Sep-11 4:59

Please check my program if it is correct

21-Sep-11 4:59

Wrong forum, ask in JavaScript next-door.

mastdesi20-Sep-11 16:47

mastdesi

20-Sep-11 16:47

I have to do my first assignment for my java class for friday this week. So due in 3 days. I wrote the polynomial class but haven't done the driver for it yet as i don't know if my polynomial class is good. Please check and let me know if i have done correctly according to my assignment details (assignment pdf file can be downloaded here http://www.2shared.com/document/7YITxJL1/A1_online.html[^]). I am missing the numberOfTerms as i can't seem to figure that out.

Please help me out.

Polynomial.java

Java

public class Polynomial
{
	private int[] coeff = new int[5];
	public Polynomial()
	{
		coeff = null;
	}
	// constructor with 5 parameter 
	public Polynomial(int c0, int c1, int c2, int c3, int c4)
	{
		this.coeff[0] = c4;
		this.coeff[1] = c3;
		this.coeff[2] = c2;
		this.coeff[3] = c1;
		this.coeff[4] = c0;
	}
	// copy constructor  
	public Polynomial(Polynomial p)
	{
		coeff = p.coeff;

	}
	
	// Get Method
	public int getCoeff(int i)
	{
		return this.coeff[i];
	}
	
	// Set Method
	public boolean setCoef(int pos, int num)
	{
		if (pos <= 4 || pos >= 0 )
			{
			coeff[pos] = num;
			return true;
			}
		else
			return false;
	}

	// toString
	public String toString()
	{
		return coeff[4]+"X4"+" + "+coeff[3]+"X3"+" + "+coeff[2]+"X2"+" + "+coeff[1]+"X"+" + "+coeff[0];
	}
	
	// Equals
	public boolean equals(Polynomial p)
	{
		if ((p.coeff[4] != coeff[4]) ||(p.coeff[3] != coeff[3]) ||(p.coeff[2] != coeff[2]) ||(p.coeff[1] != coeff[1]) ||(p.coeff[0] != coeff[0]) )
			return false;
		return true;
	}
	
	// Add
	public Polynomial add(Polynomial p)
	{
		return (new Polynomial(p.coeff[4]+coeff[4],p.coeff[3]+coeff[3],p.coeff[2]+coeff[2],p.coeff[1]+coeff[1],p.coeff[0]+coeff[0]));
	}

	// Derivative
	public Polynomial derive()
	{
		return (new Polynomial(coeff[4]*4,coeff[3]*3,coeff[2]*2,coeff[1],0));
	}

	// Evaluate
	public double evaluate(double x){
		return coeff[4]*x*x*x*x+coeff[3]*x*x*x+coeff[2]*x*x+coeff[1]*x+coeff[0];
	}

}

Richard MacCutchan20-Sep-11 21:53

Richard MacCutchan

20-Sep-11 21:53

This forum is here to help with technical problems, not to provide a free program verification service. If your code does not work in some way then please explain where and why and people will try to help you.

Unrequited desire is character building. OriginalGriff

Nagy Vilmos20-Sep-11 23:30

20-Sep-11 23:30

The copy constructor should do a 'deep' copy:

Java

// copy constructor
public Polynomial(Polynomial p)
{
    coeff = (int[])p.coeff.clone();

}

The toString method could be improved:

Java

public String toString() {
    return coeff[4] + "X^4 + " +
        coeff[3] + "X^3 + " +
        coeff[2] + "X^2 + " +
        coeff[1] + "X + " + coeff[0];
}

The override of the equals method is wrong, the signature must be equals(Object), a standard way to do this is:

Java

public boolean equals(Object obj) {
    if (obj == null || this.getClass() != obj.getClass()) {
        // either obj is null or a different types so can't be equal
        return false;
    }
    final Polynomial other = (Polynomial)obj;

    // compare the two arrays:
    return this.coeff.equals(other.coeff);
}

Sums are hard, your evaluate method can be easily improved:

Java

public double evaluate(double x){
    return (coeff[4] * x^4) +
        (coeff[3] * x^3) +
        (coeff[2] * x^2) +
        (coeff[1] * x) +
        coeff[0];
}

Layout makes code easy to read.
Easy to read makes mistakes easier to spot.
Easier to spot mistakes makes better code.

Finally get in the habit NOW of writing JavaDoc comments for all public methods.

David Skelly21-Sep-11 3:44

21-Sep-11 3:44

Nagy Vilmos wrote:
return this.coeff.equals(other.coeff);

Does not work. The easiest way is to use Arrays.equals(a, b);

mastdesi21-Sep-11 8:33

mastdesi

21-Sep-11 8:33

thank you very much everyone for helping me out. I will take everyones suggestions into consideration and I will start working on the driver now.

TorstenH.21-Sep-11 2:03

21-Sep-11 2:03

Nagy, the equals(Polynominal p) is requested that way!

the toString() is supposed to have a bit more functionality:
The method toString method will return the string containing the equation including only the
non-zero term.

...And comments are a requested point too: Include comments in your program describing the main steps in your program.

the "driver" is simply the main-method that rocks the party. You should have that one by now if you've written the rest.

Java

// copy constructor  
	public Polynomial(Polynomial p)
	{
		coeff = p.coeff;
 
	}

That does not work - coeff is a private member. Yu need to use at least getCoeff(int i) - which returns a single int value. So that one can also not be assigned to your Array coeff[5].

Java

public Polynomial()
	{
		coeff = null;
	}

...equals kind of a head shot. Your Array is invalid from that point on as it is null.

Please use decent Hungarian Code conventions:
int iValue
Array oValues
Polynominal oPoly

As Nagy says, good structure is the job half way done.

regards Torsten
I never finish anyth...

Nagy Vilmos21-Sep-11 2:33

21-Sep-11 2:33

TorstenH. wrote:
Nagy, the equals(Polynominal p) is requested that way!

Then the person who set the paper is WRONG. Big Grin | :-D

Seriously, why teach people bad practices it makes it harder for us when they becoming worker droids.

TorstenH. wrote:
the toString() is supposed to have a bit more functionality:

The method toString method will return the string containing the equation including only the

non-zero term.

POP:

Java

public String toString() {
    StringBuilder sb = new StringBuilder();

    for (int c = 0;
            c < 5;
            c++) {
        if (this.couf[c] != 0) {
            if (sb.length() > 0) {
                if (this.couf[c] > 0) {
                    sb.append(" +");
                } else {
                    // the - sign comes for free below
                    sb.append(" ");
                }
            }
            sb.append(this.couf[c]);
            if (c > 0) {
                sb.append("X");
                if (c > 1) {
                    sb.append("^").append(c);
                }
            }
        }
    }
    return sb.toString();
}

[Do you think teacher will notice it wasn't a stoodent who wrote this?]

TorstenH. wrote:
That does not work - coeff is a private member.

You can access the member variables, even private ones, of another instance of the same class.
Also using an array clone is the most efficient way to do it.

I missed the blatant bug in the null constructor; good call.

TorstenH. wrote:
Please use decent Hungarian Code conventions:

I would discourage that. With type safe languages, the need for Hungarian notation is superfluous.

David Skelly21-Sep-11 3:57

21-Sep-11 3:57

Nagy Vilmos wrote:
Also using an array clone is the most efficient way to do it.

It's not a question of efficiency.

coeff = other.coeff.clone();

does something fundamentally different from

coeff = other.coeff;

In fact you could argue that the second form is more efficient since it creates fewer objects at runtime. But in this case it is probably not what we want to do so it is just plain wrong, never mind whether it is efficient or not.

Nagy Vilmos21-Sep-11 5:01

21-Sep-11 5:01

The second copies the array reference, a shallow copy, and means that changing the content in the new instance changes the old one too.

David Skelly21-Sep-11 5:53

21-Sep-11 5:53

Yes, but what has that got to do with efficiency? I think you are confusing "efficiency" with "correctness".

Nagy Vilmos21-Sep-11 5:55

21-Sep-11 5:55

The most efficient way to clone an array.

David Skelly21-Sep-11 22:28

21-Sep-11 22:28

clone is faster because it only does a shallow copy of the array. So if you are working with a one-dimensional array of primitives (as in this case) you will get away with it. But for other cases it might not be what you want (two-dimensional arrays don't get cloned properly, for example). For copying arrays you're better off using Arrays copyOf or System arrayCopy. Again, it's a question of correctness not efficiency. Is it efficient to be fast but wrong?

Nagy Vilmos21-Sep-11 22:58

21-Sep-11 22:58

It's a primitive array, that's why using a simple clone is the right approach in this case.

David Skelly22-Sep-11 1:31

22-Sep-11 1:31

So that's why you described clone as a "deep" copy in your original reply, then?

Nagy Vilmos22-Sep-11 1:41

22-Sep-11 1:41

Okay, I sit corrected. Looking further Array.copy(...) is a better option.

mastdesi21-Sep-11 9:14

mastdesi

21-Sep-11 9:14

lol yea the teacher wants equals(Polynominal p) so is my way right or wrong?

TorstenH.21-Sep-11 19:20

21-Sep-11 19:20

looks good at a first glance - needs some fixes (read the comments).

How do you programm? Do you use a IDE like Eclipse or Netbeans?

regards Torsten
I never finish anyth...

TorstenH.21-Sep-11 19:19

21-Sep-11 19:19

Accessing private members that way? at least bad style.

my suggestion:

Java

// copy constructor  
	public Polynomial(Polynomial p)
	{
		coeff = p.getCoeff();
 
	}

regards Torsten
I never finish anyth...

Nagy Vilmos21-Sep-11 21:48

21-Sep-11 21:48

There is no method getCoeff(), just getCoeff(int).

Seriously, I don't think accessing member variables in a constructor is necessarily bad, but I guess OP could go for the 'collapse all constructors into one' approach:

Java

public Polynomial(Polynomial p)
{
    this(p.getCoeff(0),
        p.getCoeff(1),
        p.getCoeff(2),
        p.getCoeff(3),
        p.getCoeff(4));
}

public Polynomial()
{
    this(0, 0, 0, 0, 0);
}

public Polynomial(int c0, int c1, int c2, int c3, int c4)
{
    this.coeff = new int[5];
    this.coeff[0] = c0;
    this.coeff[1] = c1;
    this.coeff[2] = c2;
    this.coeff[3] = c3;
    this.coeff[4] = c4;
}

David Skelly21-Sep-11 4:17