一种不使用Hashset方法而不允许在数组列表中显示重复项的方法

Question

So I have to make two methods:

void setUnique( boolean value)

boolean getUnique()

setUnique allows the client to set whether or not to allow duplicates( true means no duplicates, false means duplicates allowed,

getUnique is to return the current setting for unique

My assignment is I have to create a SortedIntList . java and a SortedIntListTest .java and I have to have these two methods included for when I test my list.

This is what I have so far and I already know its not correct as it has errors all over it:

public void setUnique(boolean value)
{
      if(!list.contains(value))
      {
           list.add(value);
           return index == true;

      }
      else
      {

          return index == false;
      }
}

public boolean getUnique()
{
    //return value ;
}

Now I've seen people use the hashset method. However we havnt learn that in class yet so it most likely wont be allowed to be used. I am stuck on this and would really like some help on another way of now allowing duplicates into the arraylist without using the hashset method

Answer 1

first of all above method public void setUnique(boolean value) it's return type is void but you are returning some boolean value whichis wrong.

now as per me your requirement there will be one boolean flag which indicate whether client wants duplicate values or not.

so in your class take one boolean variable "flag" and implement setter and getter for that variable. client will change that flag whenever he want to change.

now create one method which return List.

public List<Integer> getList(List<Integer> inputList){
List<Integer> list=new ArrayList<Integer>();
    if(flag){
       for(Intger i:inputList){
         if(!list.contains(i)){
          list.add(i);
         }
       }
    }
   else{
     list=inputList;
   }    
return list;
}

Answer 2

You can write SortedIntList.java like this

public class SortedIntList {

  private boolean isUnique;
  private ArrayList<Integer> arrayList = new ArrayList<>();
  public boolean isUnique() {
    return isUnique;
  }

  public void setIsUnique(boolean isUnique) {
    this.isUnique = isUnique;
  }

  public void  addElement(int element){
    //While inserting element, it will check whether isUnique is set or not    

    if(isUnique){

    //If set, then it will check whether the list contains that element, if Yes, then skip it.
        if(arrayList.contains(element)){
          return;
        }
    }
    arrayList.add(element);

  }

  // Add your custom methods for sorting purpose 

  public List getArray(){
    return arrayList;
  }
}

And SortedIntListTest.java like this

public class SortedIntListTest {
  public static void main(String[] args) {

    SortedIntList list = new SortedIntList();
    list.setIsUnique(true);
    list.addElement(10);
    list.addElement(5);
    list.addElement(10);
    list.addElement(8);
    System.out.println(list.getArray());
  }
}

Answer 3

Based on the inputs, here is the template code to fill in. To find duplicates in array list, use contains method on list

 public class SortedIntList<Integer> extends AbstractList<Integer>{

    private List<Integer> myList = new LinkedList<Integer>

    private boolean isunique;

    public void add(int value){
    Case 1: if duplicates are allowed
    //add value to myList 
    Case 2: duplicates are not allowed
    while adding you need to traverse the list if there is any such value
    //sort the list
    }

    public void setUnique(boolean unique){
    //set isUnique
    //if value is changing from non-unique to unique
    //traverse the list if there is any duplicate values remove them
    }

    public boolean isUnique(){
      return isUnique;
    }

   }