Solved

Java Hashmap:

Posted on 2003-11-20
10
789 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
Comment Utility
think you need to post a little more code...
0
 
LVL 7

Expert Comment

by:grim_toaster
Comment Utility
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
Comment Utility
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
Comment Utility
Can anyone offer guidance with removeObject method?
0
 

Author Comment

by:AntoniRyszard656
Comment Utility
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
IT, Stop Being Called Into Every Meeting

Highfive is so simple that setting up every meeting room takes just minutes and every employee will be able to start or join a call from any room with ease. Never be called into a meeting just to get it started again. This is how video conferencing should work!

 

Author Comment

by:AntoniRyszard656
Comment Utility
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
Comment Utility
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
Comment Utility
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 50 total points
Comment Utility
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
Comment Utility
;-)
0

Featured Post

Highfive + Dolby Voice = No More Audio Complaints!

Poor audio quality is one of the top reasons people don’t use video conferencing. Get the crispest, clearest audio powered by Dolby Voice in every meeting. Highfive and Dolby Voice deliver the best video conferencing and audio experience for every meeting and every room.

Join & Write a Comment

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…
Java Flight Recorder and Java Mission Control together create a complete tool chain to continuously collect low level and detailed runtime information enabling after-the-fact incident analysis. Java Flight Recorder is a profiling and event collectio…
This tutorial covers a step-by-step guide to install VisualVM launcher in eclipse.
This tutorial explains how to use the VisualVM tool for the Java platform application. This video goes into detail on the Threads, Sampler, and Profiler tabs.

743 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

Need Help in Real-Time?

Connect with top rated Experts

12 Experts available now in Live!

Get 1:1 Help Now