1번 문제

public class MyPoint {
	private int x, y;
	public MyPoint(int x, int y) {
		this.x = x;
		this.y = y;
	}
	public String toString() {
		return getClass().getName() + "(" + x + "," + y + ")";
	}
	public static void main(String[] args) {
		MyPoint a = new MyPoint(3, 20);
		System.out.println(a);
	}
}

3번 문제

import java.util.Scanner;
import java.util.StringTokenizer;

public class Question3 {
	
	public static void main(String [] args) {
		int randomNumbers[] = new int[3];
		while(true) {
			for(int i = 0; i < 3; i++) {
				randomNumbers[i] = (int)(Math.random()*3+1);
				System.out.print(randomNumbers[i] + "\\t");
			}
			System.out.println();

			if(randomNumbers[0] == randomNumbers[1] && 
					randomNumbers[1] == randomNumbers[2]) {
				System.out.println("성공");
				break;
			}
		}
	}
}

5번 문제

package util;

public class Adder {
	private int x, y;
	public Adder(int x, int y) {
		this.x = x;
		this.y = y;
	}
	public int add() {
		return x + y;
	}
}

package app;

import util.Adder;

public class Main {
	public static void main(String[] args) {
		Adder adder = new Adder(2, 5);
		System.out.println(adder.add());
	}
}

class Circle {
	private int x, y, radius;
	public Circle(int x, int y, int radius) {
		this.x = x;
		this.y = y;
		this.radius = radius;
	}
	public String toString() {
		return "(" + x + "," + y + ")" + " 반지름 " + radius;
	}
	public boolean equals(Object obj) {
		Circle c = (Circle)obj;
		if(3.14 * radius * radius == 3.14 * c.radius * c.radius) {
			return true;
		}
		else return false;
	}
}

public class CircleManager {
	public static void main(String[] args) {
		Circle a = new Circle(1, 2, 10);
		Circle b = new Circle(5, 6, 10);
		System.out.println("원 1 : " + a);
		System.out.println("원 2 : " + b);
		if(a.equals(b)) {
			System.out.println("같은 원입니다.");
		}
		else System.out.println("다른 원입니다.");
	}
}

보너스 3

import java.util.Scanner;
public class StringRotateOnEnter {
	public static void main(String[] args) {
		System.out.println("문자열을 입력하세요. 빈 칸이 나있어도 되고 영어 한글 모두 됩니다.");
		Scanner sc = new Scanner(System.in);
		String text = sc.nextLine();
		
		System.out.println("<Enter>키를 입력하면 문자열이 한 글자씩 회전합니다.");
		
		while(true){
			String key = sc.nextLine();
			if(key.equals("")) {
				String first = text.substring(0, 1);
				String last = text.substring(1);
				text = last.concat(first);
				System.out.print(text + " >> ");
			}
			else if(key.equals("q")) {
				break;
			}
			else {
				System.out.print(text + " >> ");
			}
		}
		System.out.println("종료합니다.");
	}
}