Denis Yuzvyk

I have array of my classes:

MyClass [] arr = new MyClass [] {new MyClass(), new MyClass ()};

how to make shalow copy of arr?
arr.clone() will be enough?

I have method that perform check on input.
Something like this:
func (double d) { if(Double.isNaN(d)) throw new MyException(" ... "); .... }
with JUnit i need check this method:
try { func(NAN_NUMBER); failt("should throw MyException) } catch(Exception e) { // pass }

My question is:
with what value replace NAN_NUMBER ?

Why and what Collection implementation to hold such mapping:
1) String -> String
2) String -> Object

Thanks!

Oh! you are right!
at wiki says that:
The graph shown to the left has many valid topological sorts, including:

so all ok now!

Thanks!

but it is wrong too:

2,9,10,8,11,3,5,7
reverted:
7,5,3,11,8,10,9,2
from wiki:
7,5,3,11,8,2,9,10

for this grapth, i created following input:

I found such vertex and edges:
7 -> 11,8
5 -> 11
3 -> 8,10
11 -> 2,9,10
8 -> 9

so input:
MyData d1 = new MyData("7",new String [] {"11","8"}); MyData d2 = new MyData("5",new String [] {"11"}); MyData d3 = new MyData("3",new String [] {"8","10"}); MyData d4 = new MyData("11",new String [] {"2","9","10"}); MyData d5 = new MyData("8",new String [] {"9"}); MyData d6 = new MyData("2",new String [] {}); MyData d7 = new MyData("9",new String [] {}); MyData d8 = new MyData("10",new String [] {}); String [] sorted = TopSort.topologicalSort(new MyData [] {d1,d2,d3,d4,d5,d6,d7,d8});
but result is:
2,9,10,8,11,3,5,7
but it's wrong, coz on wiki page correct result must be

The graph shown to the left has many valid topological sorts, including:

* 7,5,3,11,8,2,9,10
* 7,5,11,2,3,10,8,9
* 3,7,8,5,11,10,9,2

can you please give test data?
all my attempts failed : (
may be there is bug?

May be someone can point me to implementation of this algo?

Thanks.

Hello,
I need implement topological sort.
I found info about this type of sorting on
http://en.wikipedia.org/wiki/Topological_sort
I write something like (code below).
But I can't test it .
According to wiki I get error that my graph is not a DAG, so a topological sort is impossible
My code below, Please with what input test it.
Thanks.
------------------MyData.java------------------ public class MyData { public String job; public String [] others; public MyData(String job, String [] other) { this.job = job; this.others = other; } } ---------------TopSort.java------------------- import java.util.HashMap; import java.util.HashSet; import java.util.LinkedList; import java.util.Map; import java.util.Queue; import java.util.Set; import java.util.Iterator; public class TopSort { public static String[] topologicalSort(MyData[] data) throws Exception { /* * Q ? Set of all nodes with no incoming edges while Q is non-empty do * remove a node n from Q output n for each node m with an edge e from n * to m do remove edge e from the graph if m has no other incoming edges * then insert m into Q if graph has edges then output error message * (graph has a cycle) */ int n = data.length; Map graph = new HashMap(); Queue q = new LinkedList(); String[] sorted = new String[n]; // Graph construction for (int i = 0; i < data.length; i++) { // for each statistic name s graph.put(data[i].job, new HashSet()); String[] requiredJobs = data[i].others; for (int j = 0; j < requiredJobs.length; j++) { // for each String si in requiredStats ((Set) graph.get(data[i].job)).add(requiredJobs[j]); } // Initial nodes in q if (((Set) graph.get(data[i].job)).size() == 0) q.add(data[i].job); } // Getting the nodes in sorted order int index = 0; while (q.size() > 0) { String s = (String) q.remove(); sorted[index++] = s; Iterator iter = graph.keySet().iterator(); while (iter.hasNext()) { // for each key in graph // check if node is not already removed Object key = iter.next(); if (((Set) graph.get(key)).size() != 0) { ((Set) graph.get(key)).remove(s); // if this node now has zero incoming edges if (((Set) graph.get(key)).size() == 0) { q.add(key); } } } } if(index<n) throw new Exception("Cycle detected, exiting ...."); return sorted; } public static void main(String[] args) throws Exception { MyData d1 = new MyData("job1",new String [] {"job3","job5","job4"}); MyData d2 = new MyData("job3",new String [] {"job5","job6"}); MyData d3 = new MyData("job4",new String [] {"job2","job7"}); MyData d4 = new MyData("job7",new String [] {"job1","job2","job4"}); String [] sorted = TopSort.topologicalSort(new MyData [] {d1,d2,d3,d4}); for (int i = 0; i < sorted.length; i++) { System.out.println(sorted[i]); } } }

Tanks Sanjeev Singh.
I had second type of question.
But how to detect it? I need throw exeption if duplicates detected.
[ January 19, 2007: Message edited by: Denis Yuzvyk ]

Hi,
Is there any "correct" way to find duplicates at array.

String [] arr = new String [] {"1","2","3","1"}; Map repeated = new HashMap(); for (String val : arr) { if(repeated.containsKey(val)) throw new IAE("duplicaes found"); repeated.put(val,"1"); }

Thanks

Thanks!
this is what i need!

This was 1 thing i try, but i get compilation error:

java.lang.Error: Unresolved compilation problem:
The method clone() is undefined for the type Map
if I change to:
Collections.unmodifiableMap( (Map)((Object) statistics).clone() )
i got error:
java.lang.Error: Unresolved compilation problem:
The method clone() from the type Object is not visible

According to docs, method clone available at Map implementations ...

So advice please what to do.

Thanks

Thanks.
unmodifiableMap - this is what i need.
Collections.unmodifiableMap(((HashMap)statistics).clone());

but i have question about clone.
How to know to which Map implementation cast statistics to call "clone()" method?

hi friends,

Can you please explain this:

in function "public func (java.util.Map statistics)"
task is:
Get an immutable wrapper map around the clone (using java.util.Collections)

Thans

i have someexpirience in java/jsp and i wonna write e-shop in educational purposes.But i don't know how to start. I think may be y can share some ideas, articles , etc ...
Thx , regards, Denis.