[Java] String to int, int to String 형변환

	int num = 123; String str = "789";
	// int to String
	String str1 = String.valueOf(num);
	String str2 = Integer.toString(num);
	String str3 = "" + num;
	System.out.println( str1 + " | " + str2 + " | " + str3 ); //123 | 123 | 123
	// String to int
	int num1 = Integer.parseInt(str);
	int num2 = Integer.valueOf(str); //자바 8의 Optional을 이용하여 String을 int로 변환
	int num3 = Optional.of(str).map(Integer::valueOf).get();
	System.out.println( num1 + " | " + num2 + " | " + num3 ); //789 | 789 | 789