Question

What I’m looking for is a two dimensional array of Strings. Where Strings in the same row should be unique, but with allowing row duplicates.

I’m using a list where each row is a set:

List<Set<String>> bridges = new ArrayList<Set<String>>();

I have a method that returns a set of strings:

Set<String> getBridges(){
    Set<String> temp = new HashSet<String>();
    // Add some data to temp
    temp.add("test1");
    temp.add("test2");
    temp.add("test3");
    return temp;
}

Now in the main method, I’ll call getBridges() to fill the list that I have:

List<Set<String>> bridges = new ArrayList<Set<String>>();

Set<String> tempBridge = new HashSet<String>();

for(int j=0;j<5;j++){
            for(int k=0;k<8;k++){
                        // I call the method and store the set in a temporary storage
                tempBridge = getBridges();
                        // I add the the set to the list of sets
                bridges.add(tempBridge);
                        // I expect to have the list contains only 5 rows, each row with the size of the set returned from the method
                System.out.println(bridges.size());
            }
}

Why I’m getting the list as a one dimensional array of the size 5*8? how to fix this?

Answer 1

You need to fix your loop:

List<Set<String>> bridges = new ArrayList<Set<String>>();

Set<String> tempBridge = new HashSet<String>();

for(int j=0;j<5;j++){    
    tempBridge = getBridges();
    bridges.add(tempBridge);
    System.out.println(bridges.size());
}    


Set<String> getBridges(){
    Set<String> temp = new HashSet<String>();
    for(int k=0;k<8;k++){
        // Add some data to temp
        temp.add("test" + Integer.toString(k));
    }
    return temp;
}