Java Study 2

1. Constructor

• 클래스와 동일한 이름이어야 한다
• 파라미터 개수와 타입이 다르면 이름을 중복해서 사용할 수 있다.
• 특별한 메소드
• 반환 데이터형이 없다

import java.util.Scanner;
public class test1 {
	public static void main(String[] args) {
		System.out.println("====생성자 Calu의 a====");
		Calu a = new Calu(); // cnt + 1
		a.Input();
		a.Print();
		System.out.println("====생성자 Calu의 b====");
		Calu b = new Calu("포테이토칩");
		b.Print();
		System.out.println("====생성자 Calu의 c====");
		Calu c = new Calu(2);
		c.Print();
		System.out.println("====생성자 Calu의 d====");
		Calu d = new Calu("고구마칩",5);
		d.Print();
	}
}
class Calu{
	String producName;
	int cnt=0;
	public Calu() {
		cnt++;
	}
	public Calu(String name) {
		this.producName = name;
	}
	public Calu(int cnt) {
		this.cnt = cnt;
	}
	public Calu(String name, int cnt) {
		this.producName = name;
		this.cnt = cnt;
	}
	public void Input() {
		Scanner scan = new Scanner(System.in);
		System.out.println("상품이름 : ");
		this.producName = scan.next();
		System.out.println("개수 : ");
		this.cnt = scan.nextInt();
	}
	public void Print() {
		System.out.println(
				"상품명 : "+this.producName
				+"\n개수 : "+this.cnt
				);
	}
}

2. 배열

여러 데이터를 묶어서 사용하기 위함

import java.util.Scanner;
public class test1 {
	public static void main(String[] args) {
		String[] name = new String[] {"홍길일","홍길이","홍길삼","홍길사","홍길오"};
		int[] kor = new int[] {95,87,68,79,91};
		int[] eng = new int[] {80,95,88,71,97};
		int[] mat = new int[] {61,58,97,99,68};
		StudData[] std = new StudData[name.length];
		for(int i=0;i<std.length;i++)
			std[i]= new StudData(name[i],kor[i],eng[i],mat[i]);
		StudData.StudPrintHead();
		for(int i =0;i<std.length;i++)
			std[i].StudPrint();
		Calu c = new Calu();
		int korTotal = c.sums(kor);
		int engTotal = c.sums(eng);
		int matTotal = c.sums(mat);
		System.out.println("============================================");
		System.out.println("총합\t"+korTotal+"\t"+engTotal+"\t"+matTotal);
		double korAvg = c.average(kor);
		double engAvg = c.average(eng);
		double matAvg = c.average(mat);
		System.out.println("평균\t"+korAvg+"\t"+engAvg+"\t"+matAvg);
	}
}
class StudData{
	private String name;
	private int kor;
	private int eng;
	private int mat;
	private int total_sum;
	private double total_avg;
	private Calu c;
	public StudData() {
	}
	public StudData(String name,int kor, int eng, int mat) {
		this.name = name;
		this.kor = kor;
		this.eng = eng;
		this.mat = mat;
	}
	public void StudPrint() {
		System.out.println(
				name+"\t"+kor+"\t"+eng+"\t"+mat+"\t"+StdSum()+"\t"+StdAvg()
				);
	}
	public static void StudPrintHead() {
		System.out.println("이름\t국어\t영어\t수학\t합계\t평균");
	}
	public int StdSum() {
		return kor+eng+mat;
	}
	public double StdAvg(){
		return (kor+eng+mat)/3;
	}
}
class Calu{
	public int sums(int[] temp) {
		int result = 0;
		for(int i=0;i<temp.length;i++) {
			result = result + temp[i];
		}
		return result;
	}
	public double average(int[] temp) {
		double result = 0;
		for(int i=0;i<temp.length;i++) {
			result = result + temp[i];
		}
		return result/temp.length;
	}
}