Where/how to create new object in loop

Question

Say that I have a textfile that Im looping through each line in. The text files lines look like this:

I also have a class called DataHolder that I want a new instance of with each segment (where a segment is the lines 1 2 3 4). The DataHolder class has variables for 1 2 3 and 4. When the iterator hits the whitespace, a new object of the DataHolder class should be created for the next 1 2 3 4.

How can I accomplish this ? This is what I have at the moment

File theFile = new File(pathToFile);
try
{
    Scanner fileContent = new Scanner(theFile);
    DataHolder data = new DataHolder();
    while(fileContent.hasNextLine())
    {
        String line = fileContent.nextLine();
        if(line == "")
        {

        }
    }  
}
catch(Exception e)
{
    // ToDo
}

Read each line. If value is not empty, store the value into a List. When you hit the empty space, create the DataHolder pulling the values from the List. Then clean out the List and repeat — Ascalonian
– Ascalonian, Commented Feb 4, 2015 at 20:15
new DataHolder() instantiates a new object. You can perform such an action inside your loop as well as out. Of course, you need to do something with the new instance (assign it to a variable, put it in a collection, ...) for that to be any use. — John Bollinger
– John Bollinger, Commented Feb 4, 2015 at 20:15

Ascalonian · Accepted Answer · 2015-02-04 20:21:04Z

3

File theFile = new File(pathToFile);
try
{
    Scanner fileContent = new Scanner(theFile);
    List<DataHolder> dataList = new ArrayList<DataHolder>();
    List<String> stringList = new ArrayList<String>();
    while(fileContent.hasNextLine())
    {
        stringList.add(fileContent.nextLine());
        if(line.equals(""))
        {
            if (!stringList.isEmpty())
            dataList.add(new DataHolder(stringList));
            stringList.clear();

        }
    }  
}
catch(Exception e)
{
    // ToDo
}

edited Feb 4, 2015 at 20:21

Ascalonian

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answered Feb 4, 2015 at 20:18

Marcin D

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2 Comments

Evan Bechtol Over a year ago

While Brian's answer is good, this is the completed code snippet.

Victor Over a year ago

Just a minor comment, you could close the resources.

Brian Agnew · Accepted Answer · 2015-02-04 20:12:41Z

3

This:

if(line == "")

is incorrect since you're comparing references. You should use

if(line.equals(""))

Then you can reliably compare strings, and then re-initialise your DataHolder object in the loop via:

if(line.equals("")) {
   data = new DataHolder();
}

Presumably you need to store a collection of DataHolders, in which case you would add it to the collection here. Perhaps also investigate String.trim(), such that multiple whitespaces don't break your parsing.

answered Feb 4, 2015 at 20:12

Brian Agnew

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3 Comments

Ascalonian Over a year ago

This only provides part of the answer. This doesn't set the variables in DataHolder

Brian Agnew Over a year ago

It's not what he's asked for (despite that section being missing in the code)

Ascalonian Over a year ago

It seems like that is what they are asking: The DataHolder class has variables for 1 2 3 and 4. and then DataHolder class should be created for the next 1 2 3 4.

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