Making all values in an array unique

Question

Im making a small school project, keep in mind i'm a beginner. Im gonna make a small system that adds member numbers of members at a gym to an array. I need to make sure that people cant get the same member number, in other words make sure the same value doesnt appear on serveral index spots.

So far my method looks like this:

public void members(int mNr){
    if(arraySize < memberNr.length){
        throw new IllegalArgumentException("There are no more spots available");
    } 
    if(memberNr.equals(mNr)){
        throw new IllegalArgumentException("The member is already in the system");
    }
    else{
        memberNr[count++] = mNr;
    } 
}

While having a contructor and some attributes like this:

int[] memberNr; 
int arraySize;
int count; 

public TrainingList(int arraySize){
    this.arraySize = arraySize;
    this.memberNr = new int[arraySize];
}

As you can see i tried using equals, which doesnt seem to work.. But honestly i have no idea how to make each value unique I hope some of you can help me out Thanks alot

An array will never be "equals" to an int. You need to test if the array contains the int. — Elliott Frisch
– Elliott Frisch, Commented Nov 23, 2019 at 15:35

ali sarkhosh · Accepted Answer · 2019-11-23 15:40:20Z

3

You can use set in java

Set is an interface which extends Collection. It is an unordered collection of objects in which duplicate values cannot be stored.

mport java.util.*; 
public class Set_example 
{ 
    public static void main(String[] args) 
    { 
        // Set deonstration using HashSet 
        Set<String> hash_Set = new HashSet<String>(); 
        hash_Set.add("a"); 
        hash_Set.add("b"); 
        hash_Set.add("a"); 
        hash_Set.add("c"); 
        hash_Set.add("d"); 
        System.out.print("Set output without the duplicates"); 

        System.out.println(hash_Set); 

        // Set deonstration using TreeSet 
        System.out.print("Sorted Set after passing into TreeSet"); 
        Set<String> tree_Set = new TreeSet<String>(hash_Set); 
        System.out.println(tree_Set); 
    } 
}

answered Nov 23, 2019 at 15:40

ali sarkhosh

1931 silver badge12 bronze badges

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

2 Comments

Thor Christensen Over a year ago

Im not allowed to use sets, it has to be a regular array unfortunately

ali sarkhosh Over a year ago

for (int i = 0; i < memberNr.length; i++) {      for (int j = i + 1 ; j < memberNr.length; j++) {           if (memberNr[i].equals(memberNr[j])) {                    // got the duplicate element           }      }  }

xavi4_4_4 · Accepted Answer · 2019-11-23 16:05:48Z

2

public void members(int mNr){
    if(arraySize < memberNr.length){
        throw new IllegalArgumentException("There are no more spots available");
    } 
    //You need to loop through your array and throw exception if the incoming value mNr already present
    for(int i=0; i<memberNr.length; i++){
       if(memberNr[i] == mNr){
         throw new IllegalArgumentException("The member is already in the system");
        }
     }
    //Otherwise just add it
     memberNr[count++] = mNr;
}

I hope the comments added inline explains the code. Let me know how this goes.

answered Nov 23, 2019 at 16:05

xavi4_4_4

8810 bronze badges

3 Comments

Thor Christensen Over a year ago

Thanks alot, easy to understand and it works perfectly - might have learned something new today!

xavi4_4_4 Over a year ago

Good to know that. Cheers and great day ahead.

Matthias Over a year ago

You can also use ArrayUtils.contains or the Stream API as described here if you want to get rid of the for-loop.

arun · Accepted Answer · 2019-11-23 15:51:29Z

0

Hey you can’t directly comparing arrays (collection of values with one integer value) First iterate the element in membernr and check with the integer value

answered Nov 23, 2019 at 15:51

arun

265 bronze badges

Collectives™ on Stack Overflow

Making all values in an array unique

3 Answers 3

2 Comments

3 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

2 Comments

3 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related