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Printing an array alphabetically

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Printing an array alphabetically

Apr 11th, 2009

Hi,

I'm pretty new to java and I'm not asking for anyone to do any coding for me. I just need pointing in the right direction.

How do I go about printing out the objects of an array sorted alphabetically by name without altering the original array. I know I can't use the .sort method to achieve this and I don't want to make a new temp array to do this either.

I know I have to use the compareTo method somewhere....

I'm just confused

Any help appreciated
Thanks

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Re: Printing an array alphabetically

Apr 11th, 2009

More details are needed.

For example, what type of goal are you trying to achieve? Finding a low-running time way of printing your array or just getting the job done?

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The Iterative/Recursive approach

T, V, E, D, A, B

T is found
V is found, V should be printed after T
E is found, E should be printed before T
D is found, D should be printed before T, before E
A is found, A should be printed before T, before E, before D
B is found, B should be printed before T, before E, before D but after A

Once all of the indexes in the array are reached, recursively print the results correctly.

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Re: Printing an array alphabetically

Apr 11th, 2009

I have no idea why you want to do this! What's wrong with sorting a copy? Remember that the copy array, like the original, is simply an array of references (like pointers) to the Strings; you won't copy the actual Strings unless you go out of your way so to do.

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Re: Printing an array alphabetically

Apr 11th, 2009

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Originally Posted by Alex Edwards

More details are needed.

For example, what type of goal are you trying to achieve? Finding a low-running time way of printing your array or just getting the job done?
Help with Code Tags

(Toggle Plain Text)
The Iterative/Recursive approach

T, V, E, D, A, B

T is found
V is found, V should be printed after T
E is found, E should be printed before T
D is found, D should be printed before T, before E
A is found, A should be printed before T, before E, before D
B is found, B should be printed before T, before E, before D but after A

Once all of the indexes in the array are reached, recursively print the results correctly.
The Iterative/Recursive approach T, V, E, D, A, B T is found V is found, V should be printed after T E is found, E should be printed before T D is found, D should be printed before T, before E A is found, A should be printed before T, before E, before D B is found, B should be printed before T, before E, before D but after A Once all of the indexes in the array are reached, recursively print the results correctly.

Thanks for your quick response.

I am looking for a way of using as little code as possible and using any of the java library classes available for the job.

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Re: Printing an array alphabetically

Apr 11th, 2009

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Originally Posted by JamesCherrill

I have no idea why you want to do this! What's wrong with sorting a copy? Remember that the copy array, like the original, is simply an array of references (like pointers) to the Strings; you won't copy the actual Strings unless you go out of your way so to do.

lol ok ok thats why i obviously need help....

so for example... I have an array of contact items (each consisting of first names, surnames and numbers) and I create a temp array... then how do I sort the temp array in order of their surnames so they can be printed

thanks

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Re: Printing an array alphabetically

Apr 11th, 2009

Since any Java-API based class is valid for the assignment....

I suggest inserting the values into a B-Tree (Binary Tree) then printing the objects in the tree via In-order traversal.

 Help with Code Tags 
 java Syntax (Toggle Plain Text) 
import java.util.TreeSet;
import java.util.SortedSet;
 
public class TreeSet_Test{
 
	public static void main(String... args){
 
		String values[] = {"T", "V", "E", "D", "A", "B"};
 
 
		TreeSet<String> tree = new TreeSet<String>();
 
		for(String element : values)
			tree.add(element);
 
		SortedSet<String> result = tree.tailSet("A");
 
		for(String element : result)
			System.out.print(element + " ");
	}
 
}
import java.util.TreeSet;
import java.util.SortedSet;

public class TreeSet_Test{

	public static void main(String... args){

		String values[] = {"T", "V", "E", "D", "A", "B"};


		TreeSet<String> tree = new TreeSet<String>();

		for(String element : values)
			tree.add(element);

		SortedSet<String> result = tree.tailSet("A");

		for(String element : result)
			System.out.print(element + " ");
	}

}

Last edited by Alex Edwards; Apr 11th, 2009 at 1:16 pm.

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Re: Printing an array alphabetically

Apr 11th, 2009

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Originally Posted by Alex Edwards

Since any Java-API based class is valid for the assignment....

I suggest inserting the values into a B-Tree (Binary Tree) then printing the objects in the tree via In-order traversal.

I appreciate your help...

but did i mention I was pretty new to java lol

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Re: Printing an array alphabetically

Apr 11th, 2009

Create a copy of your array and sort it using the built-in sort method, but with a custom Comparator...
define your own comparator (see the API) for your Contact class, which calculates its results by simply comparing the surnames.
See http://www.javaworld.com/javaworld/j...rt.html?page=2 for more details

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Re: Printing an array alphabetically

Apr 11th, 2009

ok... back to basics

I would just like to sort my arraylist of contacts alphabetically by name.
I have different types of contacts... with contact being the superclass (and is also an abstract class). I have also tried to create a comparable interface... but when I come to implement it I get an error... something to do with my abstract class.

I'm getting really confused now... I just thought it would be a simple process...

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Re: Printing an array alphabetically

#10

Apr 11th, 2009

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Originally Posted by JamesCherrill

Create a copy of your array and sort it using the built-in sort method, but with a custom Comparator...
define your own comparator (see the API) for your Contact class, which calculates its results by simply comparing the surnames.
See http://www.javaworld.com/javaworld/j...rt.html?page=2 for more details

Thanks... i'll have a look now... you must have read my mind... I was posting my message before I saw yours