One of the basic data structures in Python is the dictionary, which allows one to record “keys” for looking up “values” of any type. Is this implemented internally as a hash table? If not, what is it? 4 Answers 4
As per my understanding I think: It is perfectly legal for two objects to have the same hashcode. If two objects are equal (using the equals() method) then they have the same hashcode. If two objects are not equal then they cannot have the same hashcode Am I correct? Now if am correct, I have … Read more
HashMap has two important properties: size and load factor. I went through the Java documentation and it says 0.75f is the initial load factor. But I can’t find the actual use of it. Can someone describe what are the different scenarios where we need to set load factor and what are some sample ideal values … Read more
Recently I have conversation with a colleague about what would be the optimal way to convert List to Map in Java and if there any specific benefits of doing so. I want to know optimal conversion approach and would really appreciate if any one can guide me. Is this good approach: List<Object[]> results; Map<Integer, String> … Read more
What’s the (fastest/cleanest/straightforward) way to convert all keys in a hash from strings to symbols in Ruby? This would be handy when parsing YAML. my_hash = YAML.load_file(‘yml’) I’d like to be able to use: my_hash[:key] Rather than: my_hash[‘key’] 31 Answers 31 Here’s a better method, if you’re using Rails: params.symbolize_keys The end. If you’re not, … Read more
I have two HashMap objects defined like so: HashMap<String, Integer> map1 = new HashMap<String, Integer>(); HashMap<String, Integer> map2 = new HashMap<String, Integer>(); I also have a third HashMap object: HashMap<String, Integer> map3; How can I merge map1 and map2 together into map3? 17 Answers 17
Would this be the best way to sort a hash and return Hash object (instead of Array): h = {“a”=>1, “c”=>3, “b”=>2, “d”=>4} # => {“a”=>1, “c”=>3, “b”=>2, “d”=>4} Hash[h.sort] # => {“a”=>1, “b”=>2, “c”=>3, “d”=>4} 12 Answers 12
If I pass the same key multiple times to HashMap’s put method, what happens to the original value? And what if even the value repeats? I didn’t find any documentation on this. Case 1: Overwritten values for a key Map mymap = new HashMap(); mymap.put(“1″,”one”); mymap.put(“1″,”not one”); mymap.put(“1″,”surely not one”); System.out.println(mymap.get(“1”)); We get surely not … Read more
I’m requesting data from a server which returns data in the JSON format. Casting a HashMap into JSON when making the request wasn’t hard at all but the other way seems to be a little tricky. The JSON response looks like this: { “header” : { “alerts” : [ { “AlertID” : “2”, “TSExpires” : … Read more
This question already has answers here: Error java.lang.OutOfMemoryError: GC overhead limit exceeded (22 answers) Closed 2 years ago. I am getting this error in a program that creates several (hundreds of thousands) HashMap objects with a few (15-20) text entries each. These Strings have all to be collected (without breaking up into smaller amounts) before … Read more
