Having access issues with factory method objects in HashMap

Question

I am having compiler issues with the syntax and want this method to work on the Hashmap object myMap. I need the Add method to take a String value and use the Hashmap put function to add a (key, value) pair.

I tried to put the factory method initiation of newMap inside main and had access issues.

 import java.util.*;

  public class MyMap {

  public static String item;
  public static String brand;

  Map<String, String> myMap = newMap();

   public static void main(String[] args) {

    myMap.Add("apple");   

   }

   public static HashMap<String, String> newMap() {
   return new HashMap<>(); 
    } 

   public static void Add(String item)  {
    String brand = "nobrand";
    myMap.put(item, brand);
  }   


}

compilation error due to static/non static items. I made them all static to make everything accessible throughout the class.

Answer 1

You have two mistakes:

First you should make myMap static like this:

static Map<String, String> myMap = newMap();

Second you should change myMap.Add("apple"); to Add("apple"); because you write a method for main class not for HashMap that you expect to call it like that and also Add method is static and has access to myMap .

Total class would be like this:

import java.util.HashMap;
import java.util.Map;

public class Test {

    public static String item;
    public static String brand;

    static Map<String, String> myMap = newMap();

    public static void main(String[] args) {

        Add("apple");

    }

    public static HashMap<String, String> newMap() {
        return new HashMap<>();
    }

    public static void Add(String item) {
        String brand = "nobrand";
        myMap.put(item, brand);
    }

}

Answer 2

I agree with all @Spara answer

I would like to give a little more help

package com.goriant.stackoverflow.answers;

import java.util.HashMap;
import java.util.Map;

public class MyMap {

    private static final String DEFAULT_BRAND = "no_brand";
    /**
    * item - brand Map
    */
    private Map<String, String> brandMap;

    /**
    * constructor
    */
    public MyMap() {
        this.brandMap = new HashMap<>();
    }

    /**
    * add item with default brand
    * @param item
    */
    public void addItem(final String item) {
        this.brandMap.put(item, DEFAULT_BRAND);
    }

    /**
    * get brand by item
    * @param item
    * @return brand or null if there is no item in brandMap
    */
    public String getBrandByItem(final String item) {
        return this.brandMap.get(item);
    }

    /**
    * This is using for testing MyMap class
    * @param args
    */
    public static void main(String[] args) {

        // init MyMap - final is my habit :)
        final MyMap myMap = new MyMap();

        // add apple with default no_brand
        myMap.addItem("apple");

        // assert that your brand item is nobrand
        assert myMap.getBrandByItem("apple") == DEFAULT_BRAND;
    }
}

Revise at 2022-03-01

If you run this class with Java version <14, please pass flag to enable assertion feature

java -ea com.goriant.stackoverflow.answers.MyMap

You can refer github source code here: https://github.com/goriant-com/stackoverflow/blob/master/src/main/java/com/goriant/stackoverflow/answers/MyMap.java