I want to only change the int value of a specific item in a LinkedList, to a new int value. I would also like to understand the logic of how it is done, not only the code.

p.s I can not change anything, I can only add to the inside of the methods.

Thank you.

For example: [Green tea, 1] to [Green tea, 2]

The method where this needs to happen

public void changeItemCount(int k, int m){

}

Class where the question is

import java.util.LinkedList;
import java.util.ListIterator;

public class GroceryList {


    //this class will create an object that contains a list of Grocery Items
    
    //variable
    private LinkedList<GroceryItem>   glist;  //holds GroceryItems
      
    
    //constructor: instantiates glist to an empty groceryList
        
    public  GroceryList()  {
         glist = new LinkedList<GroceryItem>();
        
    }       
    
    // return number of GroceryItems in glist
    public int getSize() {  
        return glist.size();
    }
    
    //return GroceryItem at requested index 
    public GroceryItem getItem(int k) {
        GroceryItem m = glist.get(k);
        return m;
    }
    
    //add GroceryItem  x to end of glist
    public void addItem(GroceryItem  x)  {  
        glist.add(x);
    } 
    
    //Remove item at index k from glist
    public GroceryItem  removeItem(int k )  {  
        return glist.remove(k);
    } 
    
    
    //change item count for k item in glist to m
    public void changeItemCount(int k, int m) {
        //need help here
    }
    
   
    //Should work as is
    public void sortList( ) {  
        glist.sort(null); 
        System.out.println("Sorted GroceryList: "   glist);
    }  


}

other class in relation:

public class GroceryItem implements Comparable<GroceryItem> {

    
    //this class will create items from a Grocery Store and the desired quantity
    
    //variables
     private String name;   //grocery item name
     private int count;     // number needed; make sure count is always >= 0
    
     
     //set count = 1; set name  = s in following constructor
     //if only a string is passed, default count is set to 1
     public GroceryItem ( String s) { 
         count = 1;
         name = s;
     } 
  
    //constructor
     // set name = s  and set count = initCount  in following constructor
     //if a string and an int are passed then we set them to the passed values
     public GroceryItem ( String s , int initCount) { 
         name = s;
         count = initCount;
     }  
    
     
     //returns the current count
     public int getCount() {  
         return count;
     }
     
     //returns a fixed/known amount 
     public void setCount(int m) {  
         count = m;
     }
     
     public String getName() {  
         return name;
     }

    //@Override
    public int compareTo(GroceryItem o) {
        
        if( name.compareTo(o.getName() ) < 0) //less than compared item
            return -1;
        else if (name.compareTo(o.getName()) > 0) //greater than compared item
            return 1;
         else
            return( count - o.count); //duplicated item?
    }

    //toString method: formatting: [bananas, 3]
    public String toString() { 
     
    name.toString();
    String temp = Integer.toString(count);
    String formatt =  name   ", "   temp ;
    return formatt;     
    }


}

main driver:

public class GroceryListDriver {

//this class tests the methods of the two other classes 
    

    public static void main(String[] args) {
        // TODO Auto-generated method stub

        
        //creating 10 items in GroceryItem
        GroceryItem items1 = new GroceryItem("banana", 5);
        GroceryItem items2 = new GroceryItem("apples", 5);
        GroceryItem items3 = new GroceryItem("pea soup", 2);
        GroceryItem items4 = new GroceryItem("apples", 3);
        GroceryItem items5 = new GroceryItem("wheat bread", 2);
        GroceryItem items6 = new GroceryItem("tuna fish", 5);
        GroceryItem items7 = new GroceryItem("potatoes", 4);
        GroceryItem items8 = new GroceryItem("sourdough bread", 1);
        GroceryItem items9 = new GroceryItem("chedadar cheese", 1);
        GroceryItem items10 = new GroceryItem("green tea", 1);

        //creating groceryList called groceryList
        GroceryList groceryList = new GroceryList();
        
        //adding to the list
        
        groceryList.addItem(items1);
        groceryList.addItem(items2);
        groceryList.addItem(items3);
        groceryList.addItem(items4);
        groceryList.addItem(items5);
        groceryList.addItem(items6);
        
        groceryList.addItem(items7);
        groceryList.addItem(items8);
        groceryList.addItem(items9);
        groceryList.addItem(items10);
        
        
        //print current list
        //groceryList.printGroceryList(null);
        
        //sorting groceryList
        //groceryList.sortList();
        
        //change count of green tea to 2
        System.out.println(groceryList.getItem(9));
        
        
        
        
        
    }

}

CodePudding user response：

Try this one:

public void changeItemCount(int k, int m){
   GroceryItem item = getItem(k); //just get the item from list
   item.setCount(m); //and change the count value
}