Portfolio


@Test
public void whenInitializeSetWithDoubleBraces_containsElements() {
    Set<String> countries = new HashSet<String>() {
        {
           add("India");
           add("USSR");
           add("USA");
        }
    };
 
    assertTrue(countries.contains("India"));
}


Test$1$1$1.class
Test$1$1$2.class
Test$1$1.class
Test$1.class
Test.class


public class App{
	public static void main( String[] args )
	    {
	        HashMap<String, String> a = new HashMap<>();
	        a.put("a", "a");
	        HashMap<String, String> b = new HashMap<>(){{
	            put("b", "b");
	        }};
					System.out.println(a.getClass()); // class java.util.HashMap
	        System.out.println(b.getClass()); // class org.prgms.App$1 
	     }
}


@Test
public void whenInitializeUnmodifiableSetWithDoubleBrace_containsElements() {
    Set<String> countries = Stream.of("India", "USSR", "USA")
      .collect(collectingAndThen(toSet(), Collections::unmodifiableSet));
 
    assertTrue(countries.contains("India"));
}


List<String> list = List.of("India", "USSR", "USA");
Set<String> set = Set.of("India", "USSR", "USA");

Double Brace Initialization

장점

단점

대안

Stream Factory Methods

Java 9 Collections Factory Methods