[백엔드개발자 준비하기] 메소드

-매개변수 : x, 반환 : x
-void는 실행이후 반환되는 값이 없음
-컴파일 과정에서는 메소드가 정의되는것이 먼저이고 이후에 main문이 실행된다
-데이터 반환은 하나만 가능
-여러개의 데이터를 반환하고 싶으면 리스트나 배열을 사용해야 함
-클래스 안에 있는 함수는 메소드라고 부름
-클래스 밖에 있는 함수를 함수라고 부름
-자바에서는 전부 클래스 내부에서 함수를 선언하기 때문에 전부 메소드라고 부름
-메소드는 같은 이름으로 선언하지 못한다

*같은이름으로 선언할수 있는 조건
-매개변수의 종류가 다름
-매개변수의 갯수가 다름
 -> 메소드의 오버로딩

 

예시1

	public static int sum(int x, int y) {
		int result = x + y;
		
		return result;
	}

	public static void main(String[] args) {
		int a1 = 10;
		int b1 = 20;
		
		int a2 = 20;
		int b2 = 30;

		int a3 = 30;
		int b3 = 40;
		
		int total1 = 0;
		int total2 = 0;
		int total3 = 0;
		
		total1 = a1 + b1;
		total2 = a2 + b2;
		total3 = sum(a3, b3);
		
		System.out.println(total1);
		System.out.println(total2);
		System.out.println(total3);
	}

 

예시2

	public static void main(String[] args) {
		
		// 함수 호출
		method1();
		method2(100);
		method3(200, 300);
		
		System.out.println(method4());
		System.out.println();
		
		String data1 = method4();
		System.out.println(data1);
		System.out.println();
		
		System.out.println(method5(23));
	}
	
	// 매개변수 : x, 반환 : x
	public static void method1() {
		System.out.println("단순 실행");
		System.out.println();
	}
	
	public static void method2(int num) {
		System.out.println("num : " + num);
		System.out.println();
	}
	
	public static void method3(int num, int num2) {
		System.out.println("num : " + num);
		System.out.println("num2 : " + num2);
		System.out.println();
	}
	
	public static String method4() {
		return "데이터 반환";
	}
	
	public static String method5(int age) {
		return age + "살";
	}