일렬로 출력
System.out.print();
줄 바꿔서 출력
System.out.println();
System.out.println("JAVA");
System.out.println("Python");
System.out.println(123); //숫자형
System.out.println("456"); //문자열형
System.out.println("\"");
System.out.println("\'");
System.out.println("\\");
System.out.println(123+456);
System.out.println("123"+"456");
System.out.println(123+"456");
System.out.println("123"+456);
System.out.println("123+456");