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Thread: Java SetsAndMaps.java

  1. #1
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    Post Java SetsAndMaps.java

    I was looking for some help on one of my projects. I believe the first half is correct, but there are some complications in my second one. My professor is not giving me the help I need, any and all help will be much appreciated. It must be something small i'm missing.


    1. Write a static method sortAndRemoveDuplicates that accepts a list of integers as its parameter and
    rearranges the list's elements into sorted ascending order, as well as removing all duplicate values from
    the list. For example, the list {7, 4, -9, 4, 15, 8, 27, 7, 11, -5, 32, -9, -9} would become {-9, -5, 4, 7, 8,
    11, 15, 27, 32} after a call to your method. Use a Set as part of your solution.
    2. Write a static method is1to1 that accepts a Map<String, String> as its parameter and returns true if the
    two keys map to the same value. For example, {Darwin=206-9024, Hawking=123-4567, Newton=123-
    4567, Smith=949-0504} should return false, but {Darwin=206-9024, Hawking=555-1234, Newton=123-
    4567, Smith=949-0504} should return true. The empty map is considered 1-to-1 and returns true.


    < My code:
     
    import java.util.*;
    public class SetsAndMaps {
    	public static void main(String[] args) {
     
    		// Set <Integer>object2 = new TreeSet <Integer>();
     
    		ArrayList<Integer> object1 = new ArrayList<Integer>();
     
    		object1.add(7);
     
    		object1.add(4);
     
    		object1.add(-9);
     
    		object1.add(4);
     
    		object1.add(15);
     
    		object1.add(8);
     
    		object1.add(27);
     
    		object1.add(7);
     
    		object1.add(11);
     
    		object1.add(-5);
     
    		object1.add(32);
     
    		object1.add(-9);
     
    		object1.add(-9);
     
    		sortAndRemoveDuplicates(object1);
     
    		System.out.println(object1);
     
    		Set<Integer> object = sortAndRemoveDuplicates(object1);
     
    		System.out.println(object);
     
    		Map<String, String> people = new TreeMap<String, String>();
     
    		people.put("Darwin", "206-9024");
     
    		people.put("Hawking", "123-4567");
     
    		people.put("Newton", "123-4567");
     
    		people.put("Smith", "949-0504");
     
    		is1to1(people);
     
    		System.out.println(is1to1(people));
     
    	}
    	public static Set<Integer> sortAndRemoveDuplicates(
    			ArrayList<Integer> object1) {
    		Set<Integer> object = new TreeSet<Integer>(object1);
    		return object;
    	}
    	public static boolean is1to1(Map<String, String> people) {
    		Collection<String> names = people.values();
    		Iterator<String> iter = names.iterator();
    		while (iter.hasNext()) {
    			String element = iter.next();
    			while (iter.hasNext())
    			{
    				String nextElement = iter.next();
    				if (element == nextElement || names.isEmpty() == true) {
    					return true;
    				} else {
    					element = nextElement;
    				}
    			}
    		}
    		return false;
    	}
    }
    >
    Last edited by CrimaChronic; June 6th, 2012 at 08:35 PM. Reason: Formatting


  2. #2
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    Default Re: Java SetsAndMaps.java

    Please edit your post and wrap the code in code tags to preserve its formatting.

    Can you explain your problem and/or ask a specific java programming question?
    Show the programs output and explain what is wrong with it.
    If you don't understand my answer, don't ignore it, ask a question.

  3. #3
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    Default Re: Java SetsAndMaps.java

    [7, 4, -9, 4, 15, 8, 27, 7, 11, -5, 32, -9, -9]
    [-9, -5, 4, 7, 8, 11, 15, 27, 32]
    true
    is the output.

    it's returning true when it should be returning false.
    For example, {Darwin=206-9024, Hawking=123-4567, Newton=123-
    4567, Smith=949-0504} should return false, but {Darwin=206-9024, Hawking=555-1234, Newton=123-
    4567, Smith=949-0504} should return true
    .

  4. #4
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    Default Re: Java SetsAndMaps.java

    Please edit your post, format the code and wrap the code in code tags to preserve its formatting. Also get rid of the extra blank lines.

    One problem with the code is that it uses == to compare Strings instead of the equals() method.
    If you don't understand my answer, don't ignore it, ask a question.

  5. #5
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    Default Re: Java SetsAndMaps.java

    I'm not very good with html stuff :C idk how to use tags
    I need == because I am comparing two things

  6. #6
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    Default Re: Java SetsAndMaps.java

    == compares reference pointers and primitives.
    equals() compares the contents of objects.

    Edit your post and wrap your code with[code=java]<YOUR CODE HERE>[/code] to get highlighting. It will look like this:
    <YOUR CODE HERE>
    If you don't understand my answer, don't ignore it, ask a question.

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    Default Re: Java SetsAndMaps.java

    I've edited the post, so I should replace () with all the ==?

  8. #8
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    Default Re: Java SetsAndMaps.java

    I should replace () with all the ==
    Can you give an example of what you mean?

    You should use the equals() method to compare Strings, not the == operator.
    If you don't understand my answer, don't ignore it, ask a question.

  9. #9
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    Default Re: Java SetsAndMaps.java

    My goal: Write a static method is1to1 that accepts a Map<String, String> as its parameter and returns true if the
    two keys map to the same value. I believe I have this but it is returning true when it should be returning false. I do not know what I did wrong.

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    Default Re: Java SetsAndMaps.java

    This thread has been cross posted here:

    http://www.java-forums.org/java-applets/60516-setsandmaps-java.html

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  11. #11
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    Default Re: Java SetsAndMaps.java

    returns true if the two keys map to the same value.
    I don't understand what that means, can you explain? A Map can have more than one key.

    What are the steps the code needs to take to make that decision?
    If you don't understand my answer, don't ignore it, ask a question.

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    Default Re: Java SetsAndMaps.java

    This thread has been cross posted here:

    http://www.coderanch.com/t/583324/java/java/SetsAndMaps-java

    Although cross posting is allowed, for everyone's benefit, please read:

    Java Programming Forums Cross Posting Rules

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