Chapter 3. 연습문제

이론문제

실습 문제 1 (예시 참고함)

import java.util.Scanner;

public class Test {

	public static void main(String[] args) {
		Scanner scanner=new Scanner(System.in);
		System.out.println("알파벳 한 문자를 입력하세요>>");
		String s=scanner.next();
		char c=s.charAt(0);
		for (char a='a'; a<=c; a++) {
			for (char b=a; b<=c; b++)
				System.out.print(b);
			System.out.println();
		}
		scanner.close();
	}
}

실습문제 2

import java.util.Scanner;

public class thirdmutiply {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		
		int s[]=new int [10];
		Scanner scanner=new Scanner(System.in);
		System.out.print("정수 10개 입력>> ");
		for (int i=0; i<10; i++)
			s[i]=scanner.nextInt();
		
		for (int i=0; i<10; i++)
			if (s[i]%3==0)
				System.out.print(s[i]+" ");
	
		scanner.close();
	}

}

실습문제3

import java.util.InputMismatchException;
import java.util.Scanner;

public class number3 {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner scanner=new Scanner(System.in);
		System.out.print("정수를 입력하세요>> ");
		try {
			int a = scanner.nextInt();
			if (a%2==0)
				System.out.println("짝수");
			else
				System.out.println("홀수");
		}
		catch(InputMismatchException e) {
			System.out.println("수를 입력하지 않아 프로그램 종료합니다.");
		}
		
		finally {
			scanner.close();
		}

	}

}

실습문제4

import java.util.InputMismatchException;
import java.util.Scanner;


public class number4 {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		String day[]= {"일","월","화","수","목","금","토"};
		System.out.print("정수를 입력하세요>>");
		Scanner scanner=new Scanner(System.in);
		
		int a;	
		try {
				while (true) {
					a=scanner.nextInt();
					if (a<0) {
						System.out.println("프로그램 종료합니다.");
						break;
					}
					int i=a%(day.length);
					System.out.println(day[i]); 
				}
		}
		catch(InputMismatchException e) {
			System.out.println("경고! 수를 입력하지 않았습니다.");
		}
		finally {
			scanner.close();
		}
		
	}
}

실습문제 5

import java.util.Scanner;

public class number5 {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		int a[]=new int[10];
		Scanner scanner=new Scanner(System.in);
		for (int i=0; i<a.length; i++)
			a[i]=scanner.nextInt();
		
		for(int i=0; i<a.length; i++) {
			int min=i;
			for(int j=i+1; j<a.length; j++) {
				if (a[min]>a[j])
					min=j;
			}
			int temp=a[i];
			a[i]=a[min];
			a[min]=temp;
	}

		for(int i=0; i<a.length; i++)
			System.out.print(a[i]+" ");
		scanner.close();
	}
	
}

실습문제 6

실습문제 7

public class number7 {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		
		
		for (int i=1; i<100; i++) {
			if (i<10)
				if(i%3==0)
					System.out.println(i+" 박수한번");
				else
					System.out.println(i+" 박수없음");
			else {
				int first=i/10;
				int second=i%10;
				if ((first%3==0)&&(second%3==0))
					System.out.println(i+" 박수두번");
				else if ((first%3==0)||(second%3==0))
					System.out.println(i+" 박수한번");
				else 
					System.out.println(i+" 박수없음");
			}

		}
	}
}

실습문제 8

import java.util.Scanner;

public class number8 {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner scanner=new Scanner(System.in);
		String str[]= {"가위","바위","보"};
		System.out.println("컴퓨터와 가위바위보 게임을 합니다.");
		
		
		while(true) {
			System.out.print("가위바위보!>>");
			String a=scanner.next();
			if(a.equals("그만")) {
				System.out.print("게임을 종료합니다...");
				break;
			}
			int n=(int)(Math.random()*3);
			System.out.print("사용자="+a+", 컴퓨터="+str[n]+", ");
			if (str[n].equals("가위")) {
				if(a.equals("가위"))
					System.out.println("비겼습니다.");
				else if(a.equals("바위"))
					System.out.println("사용자가 이겼습니다.");
				else if(a.equals("보"))
					System.out.println("컴퓨터가 이겼습니다.");
				else
					System.out.println("잘못된 입력입니다.");
				}
			else if (str[n].equals("바위")) {
				if(a.equals("가위"))
					System.out.println("컴퓨터가 이겼습니다.");
				else if(a.equals("바위"))
					System.out.println("비겼습니다.");
				else if(a.equals("보"))
					System.out.println("사용자가 이겼습니다.");
				else
					System.out.println("잘못된 입력입니다.");
				}
			else  {
				if(a.equals("가위"))
					System.out.println("사용자가 이겼습니다.");
				else if(a.equals("바위"))
					System.out.println("컴퓨터가 이겼습니다.");
				else if(a.equals("보"))
					System.out.println("비겼습니다.");
				else
					System.out.println("잘못된 입력입니다.");
				}
			}
		scanner.close();
	}
}

Bonus 1

public class bonus1 {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		int intArray [][];
		intArray=new int[3][4];
		
		for(int i=0; i<3; i++)
			for(int j=0; j<4; j++)
				intArray[i][j]=(int)(Math.random()*10);
		
		for(int i=0; i<intArray.length; i++) {
			for(int j=0; j<intArray[i].length; j++)
				System.out.print(intArray[i][j]+"\t");
			System.out.println();
		}
		int i=0, sum=0;
		while(i<3) {
			for(int j=0; j<4; j++) {
				sum+=intArray[i][j];
			}
			i++;
		}
		System.out.println("합은 "+sum);
		}
	}