https://howtodoinjava.com/java/multi-threading/atomicinteger-example/
import org.springframework.util.CollectionUtils;
import org.apache.commons.collections.CollectionUtils;
public static void main(String[] args) {
List<String> nullList = null; boolean nullListEmpty = CollectionUtils.isEmpty(nullList);
System.out.println(nullListEmpty); // true
List<String> sizeZeroList = new ArrayList<>();
boolean sizeZeroEmpty = CollectionUtils.isEmpty(sizeZeroList);
System.out.println(sizeZeroEmpty); // true
}
https://partnerjun.tistory.com/42
https://offbyone.tistory.com/116
https://pandorica.tistory.com/4?category=86294
https://pilot376.tistory.com/3
https://okky.kr/article/342165
https://stackoverflow.com/questions/17506428/convert-base64-string-to-image-in-java
https://www.delftstack.com/ko/howto/java/how-to-convert-an-arraylist-to-a-string-in-java/
https://m.blog.naver.com/PostView.naver?isHttpsRedirect=true&blogId=writer0713&logNo=221122247629
1. []으로 싸주면 문자자체로 인식하는 것들. ⇒ [] + ⇒ [+] ] | ⇒ [|]
2. \를 붙여줘야 하는 것들. ( ⇒ \( ) ⇒ \) { ⇒ \{ } ⇒ \} ^ ⇒ \^ [ ⇒ \[ ] ⇒ \]
3. 자바의 특수문자는 \을 쓴다. " ⇒ \"
4. 나머지 부호들은 괜찮은 듯 하다. 확인된 것. ! # % & @ ` : ; - . < > , ~ ' ex )
https://denodo1.tistory.com/216
https://stackoverflow.com/questions/4283351/how-to-replace-special-characters-in-a-string/4283366
https://daemonjin.tistory.com/entry/mysql-java-data-type
https://codechacha.com/ko/java-regex/
https://ddangeun.tistory.com/43
https://www.javamex.com/tutorials/conversion/decimal_hexadecimal.shtml
https://dojang.io/mod/page/view.php?id=740
https://www.delftstack.com/ko/howto/java/java-split-string-by-space/ //자바에서는 공백 기준으로 split
int index = 0;
for (Test element : arrayList){
if(element.intVal == 3){
arrayIndexList.add(index);
}
// index 증가
index++;
}
for (Test element : arrayList){
if(element.intVal == 3){
// 아래처럼 indexOf(객체) 함수를 이용
arrayIndexList.add(arrayList.indexOf(element));
}
}
https://twpower.github.io/54-get-index-in-java-iterator