My code works..

Question about the task

HashMap of 10 pairs

Java Syntax, Level 8, Lesson 3

Under discussion

My code works.. but this doesn't compile in Codegym. Btw why what is the difference in line 13 between

HashMap<String, String> map = new HashMap<String, String>();

and

Map<String, String> map = new HashMap<String, String>();

Create a HashMap<String, String>, and add 10 string pairs:
watermelon - melon,
banana - fruit,
cherry - fruit,
pear - fruit,
cantaloupe - melon,
blackberry - fruit,
ginseng - root,
strawberry - fruit,
iris - flower,
potato - tuber.
Display the contents of the collection, each element on a new line.

Example output: (here we just show one line):
potato - tuber

Requirements:

Declare a HashMap variable with (String, String) pairs and immediately initialize it.
The program should not read values from the keyboard.
The program should add 10 string pairs to the collection in accordance with the conditions.
The program should display the contents of the collection on the screen, each pair on a new line.

package com.codegym.task.task08.task0802; /* HashMap of 10 pairs */ import java.util.HashMap; import java.util.Map; import java.util.Iterator; public class Solution { public static void main(String[] args) throws Exception { HashMap<String, String> map = new HashMap<String, String>(); map.put("watermelon", "melon"); map.put("banana", "fruit"); map.put("cherry", "fruit"); map.put("pear", "fruit"); map.put("cantaloupe", "melon"); map.put("blackberry", "fruit"); map.put("ginseng", "fruit"); map.put("strawberry", "flower"); map.put("iris", "flower"); map.put("potato", "tuber"); Iterator<Map.Entry<String, String>> iterator = map.entrySet().iterator(); while (iterator.hasNext()) { // Get a key-value pair Map.Entry<String, String> pair = iterator.next(); String key = pair.getKey(); // Key String value = pair.getValue(); // Value System.out.println(key + " - " + value); } } }

Comments (2)

Popular
New
Old

You must be signed in to leave a comment

Gellert Varga

Level 23 , Szekesfehervar, Hungary

25 January 2021, 21:57

"what is the difference between the two lines" - Guadalupe answered this, but i think this question only will be understandable when You already will be on Level_11~12. I think no problem if You not quite understand this topic at this Level yet.

Guadalupe Gagnon

Level 37 , Tampa, United States

25 January 2021, 17:05

Is ginseng a fruit? Map is an interface in the java.util package. This interface is implemented on all the map classes (TreeMap, HashMap, HashTable, etc). It defines a bunch of the common methods that all Maps share. You are able to cast the HashMap object to a Map variable using polymorphism (its not that complicated, its just the line of code you shared). By using the interface as a variable(or a parent class), you are restricting yourself to only the methods available by that interface and not all the methods that HashMaps have. That would be the case in any case where you use polymorphism to set a child class to a parent/interface variable:

Map<String, String> map = new HashMap<String, String>();
map.clone(); //<-- error on this line as Map doesn't have a clone() method

HashMap<String, String> hMap = new HashMap<String, String>();
hMap.clone(); // <-- this line is fine because HashMaps do have a clone() method