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Reading from a File [Java]


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#1 Cuajin   Members   -  Reputation: 155

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Posted 05 April 2012 - 05:53 AM

I am trying to read the inventory for a game in a text file. The inventory looks like this:
Sword 5
Shield 5 10
Cake
Sword 7
Shield 1 5

I need to read from a file and as I'm reading I need to know if the line read was a Sword, Shield or a Cake. Depending on what the item is I will do different things with it. It is important to know the numbers that follow the item. For example, shields have 2 ints, but swords only 1 int. The ints are the stats of the item.

Scanner read = new Scanner(new File("inventory.txt")) ;
while (read.hasNext())
{
	infile.findInLine("Shield") ;
}

Please, help me.

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#2 Plutonium   Members   -  Reputation: 349

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Posted 05 April 2012 - 09:53 AM

It's just suggestion. Make class Item, which have variables: name, stat1, stat2. Later create class extended from Item. For example shield, sword and so on. Now all items will have same size of variables, and you don't need difference reading strategy. Always will read name, stat1,stat2. And then creating object depending on name. So if it's sword, i will create Sword object where stat1 will be for example ATK.

And about reading, I think it's something with StringTokenizer. http://www.java-examples.com/parse-csv-file-using-stringtokenizer-example

#3 SimonForsman   Crossbones+   -  Reputation: 6065

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Posted 05 April 2012 - 10:27 AM

It's just suggestion. Make class Item, which have variables: name, stat1, stat2. Later create class extended from Item. For example shield, sword and so on. Now all items will have same size of variables, and you don't need difference reading strategy. Always will read name, stat1,stat2. And then creating object depending on name. So if it's sword, i will create Sword object where stat1 will be for example ATK.

And about reading, I think it's something with StringTokenizer. http://www.java-exam...kenizer-example


stringtokenizer is deprecated and you should use the split method of the String class instead.

Also rather than subclassing the Item class you could simply have the same stats for all items.

Thus a sword and a shield use exactly the same class, only with different values.

all items could thus be in the game data files as:
itemID : itemname : inventoryicon : mesh : texture : equipment slot : damage : range : armor : block : attackScript : useScript

in the inventory you then only have to store the itemID and the count for each item (and possibly additional modifications to the item if the game allows you to improve / enchant items)

attackScript and useScript would be the name of a class implementing a Script interface (you can load this class dynamically based on the name in the file using reflection avoiding the need for large switch blocks or if/else statements) effectivly making your entire system datadriven while still allowing highly custom behaviours for selected items. (adding a new type of weapon can then be done without changing a single line of code and even if custom behaviours are needed you don't have to change any of the existing classes, (You only have to add a new script and place it in your .jar or game folder)
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#4 Kyan   Members   -  Reputation: 395

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Posted 05 April 2012 - 11:34 AM

The issue here isn't obtaining the tokens, it is associating the tokens with their respective classes. Since each class is potentially different you need to deal with each on a case-by-case basis. Thus, as an extremely simple example, you'd want to do something like:
final Scanner read = new Scanner(new File("inventory.txt"));
String temp[];

while (read.hasNext()) {
	// whitespace is irrelevant
	temp = read.next().split("[ ]+");

	// first should always be the class name ...
	if(temp[0].equals("Sword") {
		// generally you'd want this in a try/catch block of some kind
		final int number0 = Integer.parseInt(temp[1]);

		// create your object, etc.
	}
	else if(temp[0].equals("Shield")){ ... }
	// etc
}
You'll need to do these even if you leverage Scanner's regex capabilities, since you have no way of generically creating classes with correctly numbered and typed arguments on the fly. If you included the class name as the identifier you could potentially use reflection, although that is something of a dubious solution here.

If your items are implemented as simple POJOs I would use object serialization with ObjectInputStream instead.

To state the obvious, using a well-known format such as JSON or XML frees you from the ardous task of parsing the file directly, which may be helpful if you find yourself generating a lot of files with variable syntax.

Other than that, an easier method is to separate the file I/O from the object creation - read your data into a table (or Map) of some kind and create your objects only when you need them. Use some kind of ID system so you can query for specific item properties. That way, you don't have to neurotically parse the file on a token-by-token basis.

stringtokenizer is deprecated and you should use the split method of the String class instead.

While not the case here, StringTokenizer still has its uses in select circumstances.

#5 Cuajin   Members   -  Reputation: 155

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Posted 06 April 2012 - 01:33 PM

Thanks guys! Very insightful. Learned a lot.




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