Go Premium for a chance to win a PS4. Enter to Win

x
?
Solved

Java Hashmap:

Posted on 2003-11-20
10
Medium Priority
?
812 Views
Last Modified: 2010-03-31
Hi

I am trying to write a simple hashmap program, to understand its use. I managed to add some objects to the hashmap, and some edges using this code. Now I would like to write a removeObject method and understand this involves testing if there are any edges then removing the object x set value from all the keysets. Could anyone look over my removeObject method here, tell me where I am going wrong?

Thanks

   ((Set)theMap.get(x)).add(y);
   ((Set)theMap.get(y)).add(x);



    HashMap theMap = new HashMap();

    boolean removeObject(Object x){
        boolean boolAns = containsObject(x);

        if(boolAns == true){
            ((Set)theMap.get(x));

            boolean boolEdge = containsEdge(x, y)

            if(boolEdge == true){
                Set keys = theMap.keySet();
                Iterator keyIter = keys.iterator();

                while(keyIter.hasNext){

                    //remove set values
                }

                theMap.remove(x);
            }
            else{
                theMap.remove(x);
            }
        }

        return boolAns;
    }

0
Comment
Question by:AntoniRyszard656
10 Comments
 
LVL 35

Expert Comment

by:TimYates
ID: 9785815
think you need to post a little more code...
0
 
LVL 7

Expert Comment

by:grim_toaster
ID: 9785944
Going through the code, I'm a little confused.  You have a call to ((Set)theMap.get(x)); which doesn't actually do anything, but I'm presuming you wanted to store the resultant Set into a variable?

What you then have is a call to another method (code would help) that determines if the passed map, and some undefined variable y, contains an edge.  If it does, then you completely empty the HashMap (which you could have done with theMap.clear(), unless there is some specific tidy-up code or something?), and then you try to remove the object from the HashMap, but if it contained an edge, the HashMap would now be empty.
0
 

Author Comment

by:AntoniRyszard656
ID: 9786255
I have posted the main methods, the program adds objects to a hashmap, and allows the objects to linked by an edge. The problem is when a object is removed from the hashmap, the edges are broken, and I think I would need to check in remove Object if the edge exists and remove all the links. I think:

x/y   y/x  y/x then I need to remove all the x links before removing the object x.



    void addObject(Object x){
        boolean boolAns = containsNode(x);

        if(boolAns != true){
            theMap.put(x, new HashSet());
        }
    }

    boolean removeObject(Object x){
        boolean boolAns = containsNode(x);

        if(boolAns == true){
            ((Set)theMap.get(x));

            boolean boolEdge = containsObjectEdge(x, y)

            if(boolEdge == true){
                Set keys = theMap.keySet();
                Iterator keyIter = keys.iterator();

                while(keyIter.hasNext){

                    //remove set values
                }

                theMap.remove(x);
            }
            else{
                theMap.remove(x);
            }
        }

        return boolAns;
    }

    void addObjectEdge(Object x, Object y){
        boolean boolAns = theMap.containsKey(x);

        if(boolAns == false){
            addObject(x);
        }

        boolAns = theMap.containsKey(y);

        if(boolAns == false){
            addObject(y);
        }

       ((Set)theMap.get(x)).add(y);
       ((Set)theMap.get(y)).add(x);
    }

0
Concerto Cloud for Software Providers & ISVs

Can Concerto Cloud Services help you focus on evolving your application offerings, while delivering the best cloud experience to your customers? From DevOps to revenue models and customer support, the answer is yes!

Learn how Concerto can help you.

 

Author Comment

by:AntoniRyszard656
ID: 9787147
Can anyone offer guidance with removeObject method?
0
 

Author Comment

by:AntoniRyszard656
ID: 9789521
I have posted the main methods, the program adds objects to a hashmap, and allows the objects to linked by an edge. The problem is when a object is removed from the hashmap, the edges are broken, and I think I would need to check in remove Object if the edge exists and remove all the links. I think:

x/y   y/x  y/x then I need to remove all the x links before removing the object x.



    void addObject(Object x){
        boolean boolAns = containsNode(x);

        if(boolAns != true){
            theMap.put(x, new HashSet());
        }
    }

    boolean removeObject(Object x){
        boolean boolAns = containsNode(x);

        if(boolAns == true){
            ((Set)theMap.get(x));

            boolean boolEdge = containsObjectEdge(x, y)

            if(boolEdge == true){
                Set keys = theMap.keySet();
                Iterator keyIter = keys.iterator();

                while(keyIter.hasNext){

                    //remove set values
                }

                theMap.remove(x);
            }
            else{
                theMap.remove(x);
            }
        }

        return boolAns;
    }

    void addObjectEdge(Object x, Object y){
        boolean boolAns = theMap.containsKey(x);

        if(boolAns == false){
            addObject(x);
        }

        boolAns = theMap.containsKey(y);

        if(boolAns == false){
            addObject(y);
        }

       ((Set)theMap.get(x)).add(y);
       ((Set)theMap.get(y)).add(x);
    }

0
 

Author Comment

by:AntoniRyszard656
ID: 9789522
I have posted the main methods, the program adds objects to a hashmap, and allows the objects to linked by an edge. The problem is when a object is removed from the hashmap, the edges are broken, and I think I would need to check in remove Object if the edge exists and remove all the links. I think:

x/y   y/x  y/x then I need to remove all the x links before removing the object x.



    void addObject(Object x){
        boolean boolAns = containsNode(x);

        if(boolAns != true){
            theMap.put(x, new HashSet());
        }
    }

    boolean removeObject(Object x){
        boolean boolAns = containsNode(x);

        if(boolAns == true){
            ((Set)theMap.get(x));

            boolean boolEdge = containsObjectEdge(x, y)

            if(boolEdge == true){
                Set keys = theMap.keySet();
                Iterator keyIter = keys.iterator();

                while(keyIter.hasNext){

                    //remove set values
                }

                theMap.remove(x);
            }
            else{
                theMap.remove(x);
            }
        }

        return boolAns;
    }

    void addObjectEdge(Object x, Object y){
        boolean boolAns = theMap.containsKey(x);

        if(boolAns == false){
            addObject(x);
        }

        boolAns = theMap.containsKey(y);

        if(boolAns == false){
            addObject(y);
        }

       ((Set)theMap.get(x)).add(y);
       ((Set)theMap.get(y)).add(x);
    }

0
 

Author Comment

by:AntoniRyszard656
ID: 9809330
Hello all,

I posted this question on hashmaps and hashsets several days ago, but I have never had any further code, after I posted more of the code as suggested.

I would much appreicate any guidance.
0
 
LVL 15

Expert Comment

by:jimmack
ID: 9823709
Hi AntoniRyszard656,

Sorry, but I'm a bit busy at the moment.  I'll try to get back to this question this evening (or tomorrow).  I've got the reference to your other question now, so if I've answered the original question you asked here, please accept one of my answers.  I'll continue in your other question when I get time.

Thanx.
0
 
LVL 15

Accepted Solution

by:
jimmack earned 200 total points
ID: 9842469
Sorry all, I should have included a link to the other question in my last comment.

http://www.experts-exchange.com/Programming/Programming_Languages/Java/Q_20793435.html
0
 
LVL 15

Expert Comment

by:jimmack
ID: 10066313
;-)
0

Featured Post

Independent Software Vendors: We Want Your Opinion

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

INTRODUCTION Working with files is a moderately common task in Java.  For most projects hard coding the file names, using parameters in configuration files, or using command-line arguments is sufficient.   However, when your application has vi…
Go is an acronym of golang, is a programming language developed Google in 2007. Go is a new language that is mostly in the C family, with significant input from Pascal/Modula/Oberon family. Hence Go arisen as low-level language with fast compilation…
The viewer will learn how to implement Singleton Design Pattern in Java.
Viewers will learn how to properly install Eclipse with the necessary JDK, and will take a look at an introductory Java program. Download Eclipse installation zip file: Extract files from zip file: Download and install JDK 8: Open Eclipse and …
Suggested Courses

772 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question