JAVA | 초기화 블럭(정적 초기화블럭, 인스턴스 초기화블럭)

Product.java

package kr.co.kihd.initialize;

public class Product {

	static int number = 0;  //공유
	int countNo;			//인스턴스별 개별생성
	
	int[] arr = new int[10];
	
	//정적 초기화 블럭(단, 한번만 실행됨)
	static {
		System.out.println("정적 초기화블럭 호출됨");
	}
	
	//인스턴스 초기화 블럭(정정멤버 사용가능함)
	{
		System.out.println("인스턴스 초기화블럭 호출됨");
		++number;
		this.countNo = Product.number;
		
		for(int i = 0; i<arr.length; i++) {
			this.arr[i] = (int)(Math.random()*10)+1;
		}
		
	}
	public Product() {
		System.out.println("기본생성자 호출됨");
	}
	
}

 

ProductTest.java

package kr.co.kihd.initialize;

import java.util.Arrays;

public class ProductTest {

	public static void main(String[] args) {
		Product product1 = new Product();
		Product product2 = new Product();
		Product product3 = new Product();
		
		System.out.println(
							" Product.number : " + Product.number +
                            " countNo : "+product1.countNo);
		System.out.println(
							" Product.number : " + Product.number +
							" countNo : "+product2.countNo);
		System.out.println(
							" Product.number : " + Product.number +
							" countNo : "+product3.countNo);
		
		System.out.println(Arrays.toString(product1.arr));
		System.out.println(Arrays.toString(product2.arr));
		System.out.println(Arrays.toString(product3.arr));
		
	}
		
}