hashmaps

How does the hash part in hash maps work?

So there is this nice picture in the hash maps article on Wikipedia: Everything clear so far, except for the hash function in the middle. How can a function generate the right index from any string? Are the indexes integers in reality too? If yes, how can the function output 1 for John Smith, 2 for Lisa Smith, etc.? ...

Hashmaps in javascript from integer keys

I am coding in javascript & I need HashMap type structure . Normally when I need hashmaps , I would use associative arrays only (with strings as keys). But this time I need integers as keys to hashmaps. So if I try to store A[1000]=obj, 1001 sized array is created & A[1001] is put as obj. Even if I try A["1000"]=obj , it still allocate...

How to call a method from another class in Java

So I have this class: public class Product { private String name, id, info ; private int quantity; public Product(String newName, String newID, String newInfo, Integer newQuantity){ setName(newName); setID(newID); setPrice(newInfo); setQuantity(newQuantity);} public void setName(String name) { this.name = name; } pub...

Android: Why to use a hashmap?

Hi, Someone told me hashmaps are rather slow. So I am just wondering whether to use a hashmap or simply a switch case logic. My requirement is this. I have a set of CountryNames and CountryCodes. My ListView displays the names of the countries. When an country name item is clicked, I must Toast the CountryCode. In such a scenario, sho...