어제 import java.sql.Connection; import main.java.com.study.jdbc.util.DBConnection; public class jdbcTest1 { public static void main(String[] args) { Connection connection = DBConnection.getInstance().getConnection(); System.out.println(connection); } } 오늘 import java.sql.Connection; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.sql.SQLException; import main.java.com.st..

JDBC 만들고 세팅하고 package main.java.com.study.jdbc.util; import java.sql.Connection; import java.sql.DriverManager; import java.sql.SQLException; import com.mysql.cj.jdbc.Driver; public class DBConnection { private static DBConnection instance = null; private DBConnection() {} public static DBConnection getInstance() { if(instance == null) { instance = new DBConnection(); } return instance; } public..

import java.util.ArrayList; import java.util.HashMap; import java.util.List; import java.util.Map; import java.util.function.BiFunction; import java.util.function.Function; public class Main4 { public static void main(String[] args) { Function fx1 = age -> age + "살"; /*함수의 매개변수로 많이 쓰인다.*/ System.out.println(fx1.apply(20)); Function fx2 = fx -> fx.apply(20) + "입니다"; /*binary Function*/ System.out..

import java.util.ArrayList; import java.util.HashMap; import java.util.List; import java.util.Map; import java.util.Map.Entry; import java.util.Set; import java.util.function.Consumer; public class Main3_copy { public static void forEachTest(Consumer consumer, List list) { /*foreEach 해체*/ for(String s : list) { consumer.accept(s); } } public static void main(String[] args) { List names = new Arr..

Consumer 람다. import java.util.ArrayList; import java.util.List; import java.util.function.Consumer; public class Main3 { public static void forEachTest(Consumer consumer, List list) { /*foreEach 해체*/ for(String s : list) { consumer.accept(s); } } public static void main(String[] args) { List names = new ArrayList(); names.add("임지현"); names.add("신경수"); names.add("고희주"); names.add("문승주"); names.ad..

Supplier 람다. import java.util.ArrayList; import java.util.List; import java.util.function.Supplier; public class Main2 { public static void main(String[] args) { List names = new ArrayList(); names.add("임지현"); names.add("신경수"); names.add("고희주"); names.add("문승주"); Supplier firstName = () -> names.get(0); /*-> 다음은 리턴, 변수명으로 뭘 가져오는지 명시 할 수 있음*/ /* names.get(0) 이것 자체로 의미 전달 안될때 변수명 firstName 을명시하면 아..