print unique values from array

Question

I need to get the unique values of the first array index and this is how I tried.

public class Array {

    public static void main(String[] args) {

        int[][] array = { 
                  {100, 12 , 0, 3},
                  {100, 177, 0, 3},
                  {100, 233, 0, 3}, 
                  {100, 144242, 0, 3},
                  {100, 14, 0, 4},  
                  {100, 12234, 0, 4},
                  {100, 134, 1, 4},
                  {2, 15, 0, 3},
                  {23, 1533, 0, 3},
                  {23, 1322, 1, 4}, 
                  {23, 13, 1, 4}, 
                  {23, 122, 1, 4},
                  {1321, 142, 1, 4},
                  {1321, 133,1, 4},
                  {3, 16, 0, 5},
                  {55, 1003, 0,3},
                  {553, 1002, 2, 6},
                  {31, 162, 0, 5},
                  {7, 1626, 0, 5},
                  {7, 2336, 0,5}           
                 };




        boolean isUnique = true;

        for(int i=0; i<= array.length; i++)
        {
             for (int j = 0; j < 1; j++)
             {
                 if (array[j]==array[j])
                 {                       

                     int riid = array[i][j];    

                     Set<Integer> uniqueNumbers = new HashSet<Integer>(Arrays.asList(riid));

                     System.out.println(riid);
                 }               
             }
         }
    }
}

my output must be 100, 2, 23, 1321, 3, 55, 553, 31 and 7. but, it doesn't give me unique values. It prints 100 100 100 100 100 100 100 2 23 23 23 23 1321 1321 3 55 553 31 7 7

How can I get the unique values of this output. i thought Set<Integer> uniqueNumbers = new HashSet<Integer>(Arrays.asList(riid)); would help. but, it didn't.

Xavier Delamotte · Accepted Answer · 2015-10-01 08:18:46Z

2

You just need to write:

    Set<Integer> uniqueNumbers = new LinkedHashSet<Integer>();
    for (int i = 0; i < array.length; i++) {
        uniqueNumbers.add(array[i][0]);
    }
    System.out.println(uniqueNumbers);

answered Oct 1, 2015 at 8:18

Xavier Delamotte

3,59921 silver badges30 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Łukasz Over a year ago

LinkedHashSet will preserve the insertion order afaik, so it's the only answer so far that uses a set and works as intended :p

Jordi Castilla Over a year ago

@Łukasz actually if you read question carefully OP does not need the Set. Is just used because OP does not finded a solution, OP only needs to print...

Maroun · Accepted Answer · 2015-10-01 08:20:10Z

1

You have many problems in your code:

i <= array.length - Arrays are zero-based in Java
Your inner loop runs from 0 to 1, what exactly are you trying to achieve here?
You're overriding the set on each iteration, which is not exactly what you want

There are many possible solutions for your problem, one of them is flatten the 2D-array (with Java 8 it's pretty easy), and then convert it to a Set:

int[] myArr = Arrays.stream(array)
            .flatMapToInt(Arrays::stream)
            .toArray();

Set<Integer> mySet = new HashSet<>(Arrays.asList(myArr));

answered Oct 1, 2015 at 8:20

Maroun

96.3k30 gold badges195 silver badges249 bronze badges

Comments

karim mohsen · Accepted Answer · 2015-10-01 08:22:02Z

0

That's simple create an ArrayList and check if it contains the first element of each array then don't add this element to the ArrayList and if it doesn't contain it add it to the ArrayList

 ArrayList<Integer> list = new ArrayList<>();
      for(int i = 0 ; i < array.length ;i++ ){
              if(!list.contains(array[i][0])){
                  list.add(array[i][0]);
              }
      }

here is the working exapmle

answered Oct 1, 2015 at 8:22

karim mohsen

2,2741 gold badge17 silver badges20 bronze badges

Comments

Jordi Castilla · Accepted Answer · 2015-10-01 09:02:46Z

-1

This condition compares same value, so will be always true:

if (array[j]==array[j])
//        ↑         ↑

In my understanding you just need to check first position:

int lastRiid = 0;

for (int i = 0; i < array.length; i++) {
    if (array[i][0] != lastRiid) {
        lastRiid = array[i][0];
        System.out.println(lastRiid);
    }
}

OUTPUT:

edited Oct 1, 2015 at 9:02

answered Oct 1, 2015 at 8:13

Jordi Castilla

27.1k8 gold badges73 silver badges113 bronze badges

5 Comments

Jordi Castilla Over a year ago

Hi @Manuli great to hear this. If this or any answer has solved your question please consider accepting it by clicking the check-mark. This indicates to the wider community that you've found a solution and gives some reputation to both the answerer and yourself. There is no obligation to do this.

user4605225 Over a year ago

Can you help me with print the list of 1st indexes which has the similar 0th index. ex - 100 - 12,177,233,144242, 14, 12234, 134

user4605225 Over a year ago

tried. but it prints only first value. :( This is what I got. 100-12 2-15 23-1533 1321-142 3-16 55-1003 553-1002 31-162 7-1626

Jordi Castilla Over a year ago

i should know where are you stuck... and can't add so much code in comments clear, please, post another question and paste here the link, I will take a look...

user4605225 Over a year ago

Jordi Castilla, here is the question. stackoverflow.com/questions/32885907/…

Collectives™ on Stack Overflow

print unique values from array

4 Answers 4

2 Comments

Comments

Comments

5 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

2 Comments

Comments

Comments

5 Comments

Your Answer

Sign up or log in

Post as a guest

Related