Can a hashmap have null values

Reads can occur without locking. So, in order to avoid any NullPointerExceptions being thrown we need have a check for nulls being returned before making any calls on returned object. Iterator; import java. Map; import java. NullPointerException at java. Email This BlogThis! No comments:. Newer Post Older Post Home. Subscribe to: Post Comments Atom.

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Just in case you wondered, there are multiple options. The surest one is miscommunication. Considering that you ca Hashtable ;. Iterator ;. Map ;. Entry ;. Set ;. Instead, we can iterate over a map using its collection views.

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Acording to your first code snipet seems ok, but I've got similar behavior caused by bad programing. Have you checked the "options" variable is not null before the put call? I'm using Struts2 2. When is executed in a class initialized by an Action class :. Seems the NullPointerException points to the put method Line number , but the problem was that de Map hasn't been initialized before.

It compiled ok since the variable is out of the method that set the value. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Collectives on Stack Overflow. Learn more. HashMaps and Null values? Ask Question.

Asked 8 years, 10 months ago. Active 4 years, 5 months ago. Viewed k times. I tried the following code without any success: options.

Improve this question. What does "without any success" imply? What's the problem? Do you get an error message? Learn how to use a Map separately, then integrate it into your program. So to search for that use " ". Only null is the correct pointer to null.