Java String 예시 1(concat, compareTo, compareToIgnoreCase, isEmpty)

package lec13.StringLec.lec01;

public class StringLec01 {

	public static void main(String[] args) {
		
		//charAt - 문자열 인덱스로 구하기
		String strCharAt = "hello, world";
		char charFirst = strCharAt.charAt(0);
		System.out.println("charFirst :" + charFirst);
		
		char charSecond = strCharAt.charAt(1);
		System.out.println("charSecond :" + charSecond);
		
		
		//concat - 문자열 합치기
		String concatStr01 = "Hello, ";
		String concatStr02 = "world!";
		concatStr01 = concatStr01.concat(concatStr02);
		System.out.println("result : " + concatStr01);
		
		String concatString03 = "Material";
		String concatString04 = " purchase. ";
		String resultString02 = concatString03.concat(concatString04);
		System.out.println("result : " + resultString02);
		
		System.out.println("=========================================");
		
		//compareTo
		//String이 같으면 0, 다르면 정수가 나온다.
		String compareStr01 = "good";
		String compareStr02 = "good";
		int resultCompare01 = compareStr01.compareTo(compareStr02);
		System.out.println("result :" + resultCompare01);
		
		String compareStr03 = "good";
		String compareStr04 = "bad";
		int resultCompare02 = compareStr03.compareTo(compareStr04);
		System.out.println("result :" + resultCompare02);
		
		System.out.println("=========================================");
		
		//comparTo vs compareToIgnoreCase
		//대문자 차이
		String compareStr05 = "good";
		String compareStr06 = "Good";
		int resultCompare03 = compareStr05.compareTo(compareStr06);
		System.out.println("result : " + resultCompare03);
		
		String compareStr07 = "good";
		String compareStr08 = "Good";
		int resultCompare04 = compareStr07.compareToIgnoreCase(compareStr08);
		System.out.println("result : " + resultCompare04);
		
		System.out.println("=========================================");
		
		//비어있는것과 null은 다르다
		//null은 메모리가 할당 자체가 안된것이다.
		String strEmpty01 = "";
		String strEmpty02 = "Hello, world!";
		boolean boolEmpty01 = strEmpty01.isEmpty();
		boolean boolEmpty02 = strEmpty02.isEmpty();
		System.out.println("result : " + boolEmpty01 + " result2 :" + boolEmpty02);
		
		
	}
	
}