chap_011. Hello worldpackage chap_01;public class _01_HelloWorld { public static void main (String[] args) { System.out.println("Hello World!!!"); }} 2. 자료형package chap_01;public class _02_DataTypes { public static void main(String[] args) { System.out.println(12); System.out.println(-34); System.out.println(3.14); System.out.println(true); System.out.println(false); System.out.println(..