How do I print out all keys in hashmap?

Question

I'm trying to learn how hashmaps work and I've been fiddling with a small phonebook program.

But I'm stumped at what to do when I want to print out all the keys.

here's my code:

import java.util.HashMap;
import java.util.*;

public class MapTester
{

private HashMap<String, String> phoneBook;

public MapTester(){
   phoneBook = new HashMap<String, String>();
}

public void enterNumber(String name, String number){
   phoneBook.put(name, number);
}

public void printAll(){
    //This is where I want to print all. I've been trying with iterator and foreach, but I can't get em to work
}

   public void lookUpNumber(String name){
    System.out.println(phoneBook.get(name));
}
}

Solution

Here we go:

System.out.println(phoneBook.keySet());

This will printout the set of keys in your Map using Set.toString() method. for example :

["a","b"]

Comments

[Sotirios Delimanolis]

Have you read the javadoc?

[azurefrog]

docs.oracle.com/javase/8/docs/api/java/util/…

[StackFlowed]

phoneBook.keySet(); --> return a set of keys !

[Gurkang]

Thank you, I didn't know that.

[jjlema]

If the answer helped you, please mark it as accepted, thank you.