자바 클래스

선언

package ch2;
import java.util.Scanner;

public class study1 {
	private int math;
	private int science;
	private int english;
	
	public study1 (int math, int science, int english)
	{
		this.math=math;
		this.science=science;
		this.english=english;
	}
	public int average ()
	{
		return (math+science+english)/3;
	}
	
}

실행

package ch2;
import java.util.Scanner;

public class RUN {
	public static void main(String[] args) {
		Scanner s = new Scanner(System.in);
		
		System.out.print("수학: ");
		int math = s.nextInt();
		System.out.print("과학: ");
		int science = s.nextInt();
		System.out.print("영어: ");
		int english = s.nextInt();
		
		study1 my = new study1(math, science, english);
		System.out.println("평균: "+my.average());
	}	
}

실행 결과

수학: 77
과학: 80
영어: 89
평균: 82

---

 

선언

package ch2;
import java.util.Scanner;

public class study1 {
	private double r;
	private double area;
	private double circle;
	
	public void read()
	{
		Scanner s = new Scanner (System.in);
		System.out.print("반지름 : ");
		r = s.nextDouble();
	}
	public double getArea() {
		area = (Math.PI * r *r);
		return area;
	}
	public double getCircle() {
		circle = Math.PI * r *2;
		return circle;
	}	
}

실행

package ch2;


public class RUN {
	public static void main(String[] args) {
		study1 a = new study1();
		
		a.read();
		
		System.out.println("원의 면적 : "+a.getArea());
		System.out.println("원의 둘레 : "+a.getCircle());		
	}
	
}

실행결과

반지름 : 15.05
원의 면적 : 711.5785900197222
원의 둘레 : 94.56193887305278

---

 

선언

package ch2;

public class number {
	private int num ;
	
	public number (int num)
	{
		this.num = num;
	}
	
	public int count ()
	{
		int cnt =0;
		while (num>0)
		{
			num/=10;
			cnt ++;
		}
		return cnt;
	}
}

실행

package ch2;
import java.util.Scanner;

public class RUN {
	public static void main(String[] args) {
		Scanner s = new Scanner(System.in);
		System.out.print("정수: ");
		int num = s.nextInt();
		
		number n = new number(num);
		System.out.println(num+"은 "+n.count()+"자리 입니다");
		
	}
}

실행결과

정수: 123456789
123456789은 9자리 입니다