자바 반복문 (for문)

기본 연습

package ch2;

public class study1 {
	public static void main(String[] args)
	{
		for (int i=1;i<=10;i++)
			System.out.println(i);
	}
}

package ch2;

public class study1 {
	public static void main(String[] args)
	{
		for (int i=2;i<=20;i+=2)
			System.out.print(i+" ");
	}
}

package ch2;
public class study1 {
	public static void main(String[] args)
	{
		int sum =0;
		for (int i=500;i<=1000;i++)
		{
			if (i%2==1)
				sum=sum+i;
		}
		System.out.printf("500~1000 사이의 홀수의 합 : %d",sum);
	}
}

package ch2;
import java.util.Scanner;

public class study1 {
	public static void main(String[] args)
	{
		Scanner a = new Scanner(System.in);
		System.out.println("숫자를 입력하세요 (홀수는 1, 짝수는 2)");
		int b = a.nextInt();
		for (int i=b;i<=100;i+=2)
		{
			System.out.printf("%d ",i);
		}
		
	}
}

package ch2;
import java.util.Scanner;

public class study1 {
	public static void main(String[] args)
	{
		int sum = 0;
		Scanner a = new Scanner(System.in);
		System.out.println("숫자를 입력하세요");
		int b = a.nextInt();
		for (int i=1;i<=b;i++)
		{
			sum = sum + i;
		}
		System.out.println(sum);
	}
}

package ch2;
import java.util.Scanner;

public class study1 {
	public static void main(String[] args)
	{
		int sum = 0;
		Scanner a = new Scanner(System.in);
		System.out.printf("first number: ");
		int b = a.nextInt();
		System.out.printf("last number: ");
		int c = a.nextInt();
		for (int i=b;i<=c;i++)
		{
			sum = sum + i;
		}
		System.out.println(sum);
	}
}

package ch2;
import java.util.Scanner;

public class study1 {
	public static void main(String[] args)
	{
		System.out.print("몇 단 ? ");
		Scanner a = new Scanner(System.in);
		int b = a.nextInt();
		for (int i=1;i<=9;i++)
		{
			System.out.printf("%d x %d = %d\n",b,i,b*i);
		}
		
	}
}

package ch2;
import java.util.Scanner;

public class study1 {
	public static void main(String[] args)
	{
		int sum=0;
		Scanner a = new Scanner(System.in);
		System.out.print("홀수의 개수를 입력하세요: ");
		int b = a.nextInt();
		for (int i=1;i<=2*b;i++)
		{
			if (i%2==1)
			{
				System.out.printf("%d ",i);
				sum = sum + i;
			}
		}
		System.out.printf("\n%d",sum);
		
	}
}

package ch2;
import java.util.Scanner;

public class study1 {
	public static void main(String[] args)
	{
		Scanner a = new Scanner(System.in);
		String b = a.nextLine();
		for (int i=b.length()-1;i>=0;i--)
			System.out.print(b.charAt(i));
		
	}
}

package ch2;
import java.util.Scanner;

public class study1 {
	public static void main(String[] args)
	{
		Scanner a = new Scanner(System.in);
		String b = a.nextLine();
		a.close();
		int L=0,s=0,cnt=0;
		for (int i=0;i<b.length();i++)
		{
			if (b.charAt(i)>='A'&&b.charAt(i)<='Z')
				L++;
			else if (b.charAt(i)>='a'&&b.charAt(i)<='z')
				s++;
			else if (b.charAt(i)>='0'&&b.charAt(i)<='9')
				cnt ++;
		}
			System.out.printf("%d %d %d",L,s,cnt);
	}
}

========= 중첩 for =========

package ch2;
import java.util.Scanner;

public class study1 {
	public static void main(String[] args)
	{
		Scanner a = new Scanner(System.in);
		System.out.print("출력할 행의 개수");
		int b = a.nextInt();
		a.close();
		for (int i=1;i<=b;i++)
		{
			for (int j=1;j<=i;j++)
				System.out.print(j);
			System.out.println("");
		}
		
	}
}

package ch2;
import java.util.Scanner;

public class study1 {
	public static void main(String[] args)
	{
		Scanner a = new Scanner(System.in);
		System.out.print("출력할 행의 개수");
		int b = a.nextInt();
		int k =1;
		a.close();
		for (int i=1;i<=b;i++)
		{
			for (int j=1;j<=i;j++)
				System.out.printf("%-2d",k++);
			System.out.println("");
		}
		
	}
}

package ch2;
import java.util.Scanner;

public class study1 {
	public static void main(String[] args)
	{
		Scanner a = new Scanner(System.in);
		System.out.print("출력할 행의 개수");
		int b = a.nextInt();
		a.close();
		for (int i=1;i<=b;i++)
		{
			for (int j =b-i;j>=0;j--)
				System.out.print(" ");
			for (int j=1;j<=i;j++)
				System.out.print(i+" ");
			System.out.println("");
		}
		
	}
}

package ch2;
import java.util.Scanner;

public class study1 {
	public static void main(String[] args)
	{
		Scanner a = new Scanner(System.in);
		System.out.print("출력할 행의 개수");
		int b = a.nextInt();
		a.close();
		int p,q;
		for (int i=1;i<=b;i++)
		{
			if (i%2==0)
			{
				p=1;
				q=0;
			}							
			else
			{
				p=0;
				q=1;
			}
			for (int j=1;j<=i;j++)
			{
				if (j%2==0)
					System.out.print(p);
				else
					System.out.print(q);
			}
			System.out.println("");
				
			
				
		}
		
	}
}

 

역별삼각형

package ch2;
import java.util.Scanner;

public class study1 {
	public static void main(String[] args)
	{
		Scanner a = new Scanner(System.in);
		System.out.print("출력할 행의 개수");
		int b = a.nextInt();
		a.close();
		for (int i=b;i>=1;i--)
		{
			for (int j=b-i;j>=1;j--)
				System.out.print(" ");
			for (int t=1;t<=i;t++)
				System.out.print("*");
			System.out.println("");
		}
		
	}
}

 

package ch2;
import java.util.Scanner;

public class study1 {
	public static void main(String[] args)
	{
		Scanner a = new Scanner(System.in);
		System.out.print("출력할 행의 개수");
		int b = a.nextInt();
		a.close();
		for (int i=1;i<=b;i++)
		{
			for (int j=b-i;j>=1;j--)
				System.out.print(" ");
			for (int t=1;t<=i;t++)
				System.out.print("@");
			System.out.println("");
		}
		
	}
}

 다이아몬드 모양 별

package ch2;
import java.util.Scanner;

public class study1 {
	public static void main(String[] args)
	{
		Scanner a = new Scanner(System.in);
		System.out.print("출력할 행의 개수 (절반)");
		int b = a.nextInt();
		a.close();
		for (int i=1;i<=b;i++)
		{
			for (int j=b-i;j>=1;j--)
				System.out.print(" ");
			for (int t=1;t<=2*i-1;t++)
				System.out.print("*");
			System.out.println("");
		}
		for (int i=b-1;i>=1;i--)
		{
			for (int j=b-i;j>=1;j--)
				System.out.print(" ");
			for (int t=1;t<=2*i-1;t++)
				System.out.print("*");
			System.out.println("");
		}
		
	}
}