알고리즘 java 자료구조 멀티스레드 non-escaping closure ios 스레드 동기화 Algorithm MVVM Capturting Value @Published escaping closure closure 축약 cloure value type closure escaping non escaping 스레드 Closure Closure capture jvm swift cloure referunce type property observer codingtest 속성감시자 Thread closure 간결 list Android Python