How do I make a search statement in java with a while loop and stop and return the object when it's found

user_8785271 0
Viewed 286

I've been stuck with this java search statement. I'm trying to search in an Array of Products called stock which is initialized in the class Stockmanager, which contains an id field a name and a stock level. these product objects are made in a separate class called Product.

constructor Stockmanager:

// A list of the products.
private ArrayList<Product> stock;

/**

 * Initialise the stock manager.

 */
public StockManager()
{
    stock = new ArrayList<>();
}

Product constructor:

// An identifying number for this product.
private int id;
// The name of this product.
private String name;
// The quantity of this product in stock.
private int quantity;

/**
 * Constructor for objects of class Product.
 * The initial stock quantity is zero.
 * @param id The product's identifying number.
 * @param name The product's name.
 */
public Product(int id, String name)
{
    this.id = id;
    this.name = name;
    quantity = 0;
}

There is an accessor method in Product to retrieve a product object id:

/**
 * @return The product's id.
 */
public int getID()
{
    return id;
}

Now in Stockmanager, I have my search method, but it seems this method will complain about incompatible datatypes if I don't use my for-each loop or will complain about not having a return statement if I do use a for-each loop.

the method: 

/**

 * Try to find a product in the stock with the given id.

 * @return The identified product, or null if there is none

 * with a matching ID.

 */
public Product findProduct(int id)
{
    int index = 0;
    boolean searching = true;

    for (Product item : stock)
    {  
       while(searching && index < stock.size())
       {
            if (item.getID() == id)
            {
                searching = false;
                return item;
            } else {
                index++;
            } 
            if(searching)
            {
                return null;
            } else {
                return item;
            }
        }
    }        
}

It's got to be possible to have a while loop in this return statement because I don't need the method to look further in the array if it's found a hit. Please, what am I doing wrong?

java
3 Answers

There's no reason to have two nested loops, and you don't need the index and searching variables.

You just need a single for loop. If you find a matching Product, you return it. If not, you return null when the loop ends.

public Product findProduct(int id)
{    
    for (Product item : stock) {  
        if (item.getID() == id) {
            return item;
        }
    }
    return null;    
}
user_12215710

In Java 8 you could use the Stream API 

public Optional<Product> findProduct(int id)
{
    return stock.stream().filter(item -> item.getID() == id).findAny();
}

Before Java 8 simply implement it using a for loop.

public Product findProduct(int id)
{
    for (Product item : stock)
    {  
       if (item.getID() == id) 
       {
                return item;
       }
    }   
    return null;     
}
user_9608750

Just Remove if(searching) condition,

/**

     * Try to find a product in the stock with the given id.

     * @return The identified product, or null if there is none

     * with a matching ID.

     */
    public Product findProduct(int id){
        for (Product item : stock){  
           if (item.getID() == id){
                return item;
            }
        } 
      return null;
    }

Why do you need while loop? There is no need of while loop.

user_31485900
Related