With Java 8 or less. You can use static block to initialize a map with some values. Example : public static Map<String,String> test = new HashMap<String, String> static { test.put("test","test"); test.put("test1","test"); } With Java 9 or more. You can use Map.of() method to initialize a map with some values while declaring. Example :

Just use eclipse and use latest JDK. Source code of Java core packages come attached with the JDK. Open HashMap class and you are good to go. Some of the method implementations may come from AbstractMap, AbstractCollection etc. This is because of proper OO design. You can navigate to all the classes of JDK in your eclipse.

I am trying to keep a temporary container of a class that contains member : HashMap&lt;Integer,myObject&gt; myobjectHashMap A class called myobjectsList Then I do myobjectsListA = new myobjectsLis...

I have this field: HashMap<String, HashMap> selects = new HashMap<String, HashMap>(); For each Hash&lt;String, HashMap&gt; I need to create a ComboBox, whose items are the value (which

May 23, 2017 · First off, Java's HashMap class is not thread safe, so there are no guarantees when reads and writes are happening concurrently. However, since reads and writes to references in Java are atomic, then the pattern you described could be thread-safe as long as the refresh code is not mutating the old map. For example, the following would be fine:

Feb 3, 2009 · To make it re-usable, we could make the map itself a parameter of the helper method, but then initialization code would not be any shorter. Third tip. The 3rd tip is that you can create a re-usable builder-like helper class with the populating functionality. This is really a simple, 10-line helper class which is type-safe:

If you need an instance of HashMap, the best way is: fileParameters = new HashMap<String,String>(); Since Map is an interface, you need to pick some class that instantiates it if you want to create an empty instance. HashMap seems as good as any other - …

Aug 8, 2013 · As we know the purpose of "final" keyword in java. While declaring a variable as final, we have to initialize the variable. like " final int a=10;" We can not change the value of "a". But if we go for HashTable its possible to add some value even declaring the HashTable as final.

Dec 17, 2015 · Java doesn't want you to make an array of HashMaps, but it will let you make an array of Objects. So, just write up a class declaration as a shell around your HashMap, and make an array of that class.

Jul 7, 2009 · @Alex "In older Java versions using pre-sized array was recommended (...) However since late updates of OpenJDK 6 this call was intrinsified, making the performance of the empty array version the same and sometimes even better, compared to the pre-sized version.