double brace initialization

Instead of having to always initialize a set, list or map to contain elements by manually initializing a set and adding elements to it (for example to pass to a function), Java provides a way to do it all in one go. It's called Double Brace Initialization. For example the following code:

public Set<String> mySet = new 
HashSet<String>();
mySet.add("one");
mySet.add("two");
mySet.add("three");

someFunction(mySet);

becomes:

someFunction(new HashSet<String>() {{
  add("one");
  add("two");
  add("three");
}});

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