Java Input/Output

Question

I am trying to create a simple reservation system. I read lines from an input, before finish the project I write them to an output file.

My input is like

ADDTRAIN,Cumhuriyet,Regional,80,90,50,40

ADDTRAIN,Baskent,Express,80,90,1,2

ADDTRAIN,Baskent,Express,80,90,50,40

If one train has a same name with another I have to write "Command Failed... Train Name: ...."

I split them for comma then i create an Arraylist for Train.

File text = new File();
    PrintWriter writer = new PrintWriter();
    Scanner scnr = new Scanner(text);
  
    while(scnr.hasNextLine()){
       
        String line = scnr.nextLine();
        String[] atts = line.split(",");
        if(atts[0].equals("ADDTRAIN"))
        {
            train.add(new Train(atts[0],atts[1],atts[2],atts[3],atts[4],atts[5],atts[6]));
        }

    for(int i= 1; i<train.size(); i++)
    {
        writer.print(train.get(i-1).Writer());
        if(train.get(i).getTrainName().equals(train.get(i-1).getTrainName()))
        {
            writer.print(train.get(i).WrongWriter());
        }
    }
    
    scnr.close();
    writer.close();

I can only check for previous line. For example if my input is like

ADDTRAIN,Cumhuriyet,Regional,80,90,50,40

ADDTRAIN,Baskent,Express,80,90,1,2

ADDTRAIN,Baskent,Express,80,90,50,40

ADDTRAIN,Cumhuriyet,Regional,80,90,50,40

My program doesn't write a "Command Failed" line to output. How can i solve this problem?

At what point in your code are you writing Command Failed?! — Bitmap
– Bitmap, Commented Apr 25, 2014 at 9:21
@Bitmap I'm guessing train.get(i).WrongWriter() returns the string? Dunno... — Duncan Jones
– Duncan Jones, Commented Apr 25, 2014 at 9:23
yeah. train.get(i).WrongWriter() write "Command Failed... Train Name:" error to the output. But it only checks previous line, not all objects. For train.get(0).getTrainName I don't need to check anything. But train.get(1) I need to check train.get(0).getTrainName. And for train.get(2) I need to check both train.get(0).getTrainName and train.get(1).getTrainName — Mert Serin
– Mert Serin, Commented Apr 25, 2014 at 9:27

Svetlin Zarev · Accepted Answer · 2014-04-25 09:31:11Z

3

You should use HashMap to store your data: Key=TrainName, Value=TrainObject. Using a HashMap provides both an easy and efficient way to check/disallow duplicates

if(trainMap.contains(trainName){ System.out.println("Error - train already exists"); }

edited Apr 25, 2014 at 9:31

answered Apr 25, 2014 at 9:21

Svetlin Zarev

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3 Comments

Duncan Jones Over a year ago

This would require all fields to be the same (or a dodgy equals method). The OP seems only interested if the name is the same.

Svetlin Zarev Over a year ago

updated my answer, As a key OP can use the train name, and as a value - the train object. As far as i understood the question, this solves the problem

Mert Serin Over a year ago

I'll try to use this.

xagyg · Accepted Answer · 2014-04-25 09:30:03Z

1

If you don't want to use a HashMap (which is a good solution), you can use two loops.

for(int i = 0; i<train.size(); i++)
{
    writer.print(train.get(i).Writer());
    for(int j = 0; j<train.size(); ++j)
    {
        if (i==j) continue;
        if(train.get(i).getTrainName().equals(train.get(j).getTrainName()))
        {
            writer.print(train.get(i).WrongWriter());
            break;
        }
    }
}

answered Apr 25, 2014 at 9:30

xagyg

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3 Comments

Svetlin Zarev Over a year ago

Two for loops is inefficient and there is more to code :)

xagyg Over a year ago

@SvetlinZarev I agree. It is just an alternative. I also prefer HashMap, but I think this option is worth mentioning anyway.

Mert Serin Over a year ago

but i never used HashMap so that would be better for me :D thanks man

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