Java Snippet

Original Post

Boredpayne

Jul 18, 2011

Boredpayne

not a super moderator anymore ;o

7th Dan Black Belt

Join Date: Nov 2009

Posts: 2,566

Jul 18, 2011

Java Snippet

Playing around with Swing and string parsing, finally bothered getting this finished.

It factors any factorable trinomial.

Not really an experienced dev, so any advice on optimization or what I'm doing stupidly would be great.

Runnable .jar file here: http://www.mediafire.com/?jol41bkku9v0mqi

Code in spoiler below.

Full code

Java code:

package factortrinomial;

import javax.swing.*;

import java.awt.*;

import java.awt.event.*;

public class FactorTrinomial extends JFrame implements ActionListener{

    public static final int WIDTH=400;

    public static final int HEIGHT=200;

    public static final int NUMBER_OF_CHAR=30;

    public static String output;

    

    private JTextField trinomial;

    

    public static void main(String[] args){

        FactorTrinomial gui = new FactorTrinomial();  //creates an object, or window, using the no argument constructor below to set up its layout.

        gui.setVisible(true);        

    }

    

    public FactorTrinomial(){

        super("Trinomial Factorer");

        setSize(WIDTH, HEIGHT);

        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        setLayout(new GridLayout(2,1)); //creates a grid space of two rows and a single column that encases the whole window.

        

        JPanel topPanel = new JPanel(); //creates a container which then fills the top row.

        topPanel.setLayout(new BorderLayout());

        topPanel.setBackground(Color.WHITE);

        

        trinomial = new JTextField(NUMBER_OF_CHAR);

        topPanel.add(trinomial, BorderLayout.SOUTH); //adds a text field at the bottom of the top container, near the middle.

        

        JLabel trinomialLabel = new JLabel("Enter your trinomial below (e.g. x^2+8x+16)");

        topPanel.add(trinomialLabel, BorderLayout.NORTH); //puts instructive text at the top.

        

        JLabel trinomialLabel2 = new JLabel("If the result is nonsensical, the trinomial cannot be factored");

        topPanel.add(trinomialLabel2, BorderLayout.CENTER); //puts more instructive text beneath that.

        

        add(topPanel); //adds the whole panel, including the text area and instructive texts.

    

        JPanel bottomPanel = new JPanel(); //creates the lower panel.

        bottomPanel.setLayout(new FlowLayout());

        bottomPanel.setBackground(Color.BLUE);

        

        JButton enterButton = new JButton("Enter");

        enterButton.addActionListener(this);

        bottomPanel.add(enterButton); //creates an enter button and a listener for said button.

        

        JButton clearButton = new JButton("Clear");

        clearButton.addActionListener(this);

        bottomPanel.add(clearButton); //creates a clear button to erase.

        

        add(bottomPanel);

    }

    public void actionPerformed(ActionEvent e){

        String actionCommand = e.getActionCommand(); //gets the text from the button pressed.

        if (actionCommand.equals("Enter")) {

            output=trinomial.getText();

            output=Trinomial(output);

            trinomial.setText(output);

        }

        else if(actionCommand.equals("Clear")) {trinomial.setText("");}

        else {trinomial.setText("Error");}

    }

        public static String Trinomial(String Equation){

        int counter=0,counter2=0,cTerm=0,r=0,t=0,q=1,leftTop=0;

        String Exponent="1";

        String Exponent2="1";

        String Coefficient1="1";

        String Coefficient2="1";

        String finalTerm="1";

        String Teste="";  //initializes a bunch of stuff that can't be initialized inside a loop, since that obviously ruins the loop.

        for (int i=0;i<Equation.length();i++) {

            String Tester=Equation.substring(i, i+1);

            if (Tester.equals("x")) {

                int logger=i; 

                if (Equation.substring(i+1,i+2).equals("^")) { //checks for exponents

                    for (int x=i+2;x<Equation.length();x++) {

                        String Test=Equation.substring(x, x+1);

                        if (Test.equals("+") || Test.equals("-") || Test.equals("*") || Test.equals(" ") || Test.equals("/") ){

                            if (counter==0){

                                    Exponent=Equation.substring(i+2, x);

                                    counter++;

                                    break;

                            }

                            if (counter==1){

                                Exponent2=Equation.substring(i+2, x);

                                break;

                            }

                        }

                    }

                }

                if (logger==0){

                    Coefficient1="1";

                    counter2++;

                }

                else if (logger==1){

                    Coefficient1=Equation.substring(0,1);

                    if (Coefficient1.equals("-")){Coefficient1="-1";}

                    counter2++;

                }

                else if (logger>1){

                    for (int a=i-1;a>=0;a--){

                        String Tes=Equation.substring(a, a+1);

                        if (Tes.equals(" ") || Tes.equals("+") || Tes.equals("*") || Tes.equals("/") || Tes.equals("-")){

                            if (counter2==0){

                                if (Tes.equals("-")){Coefficient1=Equation.substring(a,i);}

                                else {Coefficient1=Equation.substring(a+1,i);}

                                counter2++;

                                break;

                            }

                            if (counter2==1){

                                if (Tes.equals("-")){Coefficient2=Equation.substring(a,i);}

                                else {Coefficient2=Equation.substring(a+1,i);}

                                break;

                            }

                        }

                        if (a==0){

                            if (Equation.substring(0,i).equals("-")){Coefficient1="-1";}

                            Coefficient1=Equation.substring(0,i);

                            counter2++;

                            break;

                        }

                    }

                }

            }

        }

        for (int e=Equation.length();e>=0;e--){

            if (e==Equation.length()){

                Teste=Equation.substring(e);

            }

            else {

                Teste=Equation.substring(e, e+1);

            }

            if (Teste.equals(" ") || Teste.equals("+") || Teste.equals("-") || Teste.equals("*") || Teste.equals("/")){

                if (Teste.equals("-")){finalTerm=Equation.substring(e);}

                else {finalTerm=Equation.substring(e+1);}

                break;

            }

            

        }

        cTerm=Integer.parseInt(finalTerm);

        int coefficient=Integer.parseInt(Coefficient1);

        int topBox=0;

        int bottomBox=Integer.parseInt(Coefficient2);

        for (q=coefficient;q>1;q--){

            if (coefficient%q==0 && cTerm%q==0 && bottomBox%q==0){

                coefficient=coefficient/q;

                cTerm=cTerm/q;

                bottomBox=bottomBox/q;

                break;

            }

        }

        topBox=cTerm*coefficient;

        System.out.println(topBox+" "+bottomBox);

        done:for (r=Math.abs(topBox);r>=Math.abs(topBox)-(2*Math.abs(topBox));r--){

            for (t=Math.abs(topBox);t>=Math.abs(topBox)-(2*Math.abs(topBox));t--){

                if (t*r==topBox){

                    if (r+t==bottomBox){

                        break done;

                    }

                }

            }

        }

        if (coefficient==1){

            return (q+"(x+"+r+")(x+"+t+")");

        }

/*None of these variables are necessary; however, they make the code more explicit. This method uses the X box factoring sequence, which one needs to familiarize oneself with to understand.

This method just assumes that x is one, and the first term has an exponent of 2.

To make this more understandable: any variable with top or bottom is a common multiple outside the box. 

Anything with upper or lower are actual numbers within the box*/

    else {

        int upperLeft=coefficient;

        int upperRight=r;

        int lowerLeft=t;

        int lowerRight=cTerm;

        for (int s=Math.abs(upperRight);s>=Math.abs(upperRight)-2*(Math.abs(upperRight));s--){

            if (upperRight%s==0 && upperLeft%s==0){

                leftTop=s;

                break;

            }

        }

        int topRight=upperRight/leftTop;

        int leftBottom=lowerRight/topRight;

        int topLeft=lowerLeft/leftBottom;

        return (q+"("+topLeft+"x+"+topRight+")("+leftTop+"x+"+leftBottom+")");

    }

    }

    

}

Edit: reviewing this, it seems somewhere along the way something didn't save, this version isn't compatible with negative numbers. Will fix soon.

Last edited by Boredpayne; Jul 18, 2011 at 02:27 AM.

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Hey look more than two lines.

Quote

Gorman

Jul 18, 2011

Gorman

Elitist

Blue Belt

Join Date: Aug 2008

Posts: 7,217

Jul 18, 2011

Nicely done! I can see a lot of minor semantic/grammatical errors, but the program runs nicely. It is also good that you are looking to optimisation, just be aware that in this program it really isn't needed

I also like how you didn't use OO, since it is not necessary.

The first error I see is in naming conventions;

Naming conventions

Java code:

        String Exponent="1";



        String Exponent2="1";



        String Coefficient1="1";



        String Coefficient2="1";



        String finalTerm="1";



        String Teste="";

See the inconsistency? It is even more obvious when looking at the entire system, there are a lot of different ones!

Luckily for you Java is a very well defined language, so it is not hard to find out what should be going on, from wikipedia;
Classes: Class names should be nouns in "CamelCase", with the first letter capitalised. Try to keep your class names simple and descriptive. Use whole words — avoid acronyms and abbreviations (unless the abbreviation is much more widely used than the long form, such as URL or HTML). (well you only had one class so this wasn't a big deal, you should name it something more like "TrinomialFactoriser" to make it obvious that that is what it does. "FactorTrinomial" is more of a verb.)

Methods: Methods should be verbs, in "CamelCase", with the first letter lower case. (You did this inconsistently)

Variables: Local variables, instance variables, and class variables are also written in "CamelCase", with the first letter lower case. Variable names should not start with underscore ('_') or dollar sign ('$') characters, even though both are allowed. Certain coding conventions state that underscores ('_') should be used to prefix all instance variables, for improved reading and program understanding.
Variable names should be short yet meaningful. The choice of a variable name should be mnemonic — that is, designed to indicate to the casual observer the intent of its use. One-character variable names should be avoided except for temporary "throwaway" variables. Common names for temporary variables are i, j, k, m, and n for integers; c, d, and e for characters.

Constants: Constants should be written in uppercase characters separated by underscores. Constant names may also contain digits if appropriate, but not as the first character. (You followed this naming convention!)

Spacing

Shorthand

Repetition

Need for modules

Here is a great example;
Java code:





/*None of these variables are necessary; however, they make the code more explicit. This method uses the X box factoring sequence, which one needs to familiarize oneself with to understand.



This method just assumes that x is one, and the first term has an exponent of 2.



To make this more understandable: any variable with top or bottom is a common multiple outside the box. 



Anything with upper or lower are actual numbers within the box*/



    else {



        int upperLeft=coefficient;



        int upperRight=r;



        int lowerLeft=t;



        int lowerRight=cTerm;



        for (int s=Math.abs(upperRight);s>=Math.abs(upperRight)-2*(Math.abs(upperRight));s--){



            if (upperRight%s==0 && upperLeft%s==0){



                leftTop=s;



                break;



            }



        }



        int topRight=upperRight/leftTop;



        int leftBottom=lowerRight/topRight;



        int topLeft=lowerLeft/leftBottom;



        return (q+"("+topLeft+"x+"+topRight+")("+leftTop+"x+"+leftBottom+")");



    }



    }

The first thing that strikes me about this segment is that it REALLY should be it's own function. You have a block comment telling me about it, and it obviously works independently.
The second thing I notice is two } in line with each other. This should never happen.
The third thing I think is "he more or less says I won't understand it, yet he doesn't make it a function?". It is much easier to understand Factor than to understand all the code... Functions are a powerful abstraction method!

Trinomial is a VERY long function. It needs to be split up. In some places your nesting is 6 deep (now some of that can be reduced with shorthand, but really you need to do both shorthand and modulisation).

Agile techniques prescribe a maximum function length of 25 lines, which I think you more than double (maybe triple?). To be fair Agile is extreme, but I think that you can cut it down to <40 lines easily, which will vastly improve readability.

The last line " return (q+"("+topLeft+"x+"+topRight+")("+leftTop+"x+"+lef tBottom+")");" is another thing.
If you wanted to change the format you would have to edit that string. Rather you should make a seperate function called "ToString" or such, and have it format the string, while the other functions just call it.

It is nice, but as you can see there is a lot of room for improvement.

I suggest reading about coupling and cohesion (two topics that I didn't even really touch on, but will be hugely useful).
If you want to learn some higher level design, you could also take a look at some Design Patterns.

Quote

Boredpayne

Jul 19, 2011

Boredpayne

not a super moderator anymore ;o

7th Dan Black Belt

Join Date: Nov 2009

Posts: 2,566

Jul 19, 2011