对数的操作 开始我的JAVA历程

package Text;

public class Sumn {
	public static void main (String args[]){
		System.out.println("整数和");
		Sum S=new Sum();
		S.prient();
		System.out.println("偶数和");
		sum1 s1=new sum1();
		s1.prient();
		System.out.println("N!");
		sum2 s2=new sum2();
		s2.prient();
		System.out.println("Fibonacci数列的前N项");
		sum3 s3=new sum3();
		s3.prient();
	}

}
package Text;

public class Sum {

	public int sum(int n){

		int x=0;
		for(int i=1;i<=n;i++){
			x=x+i;
		}
		int s=x;
		return s;
	}
	public void prient(){
		System.out.println(sum(100));
	}

}

package Text;

public class sum2 {
	public int sum(int n){

		int x=1;
		for(int i=1;i<=n;i++){
			x=x*i;
		}
		int s=x;
		return s;
	}
	public void prient(){
		System.out.println(sum(10));
	}

}
package Text;
public class sum3 {
	int [] intfib=new int[20];
	public void prient(){
			int i;
			int n= 20;
			for(i=1;i<=n;i++)
			{
				if(i==1)
					intfib[0]=1;
				else if(i==2)
					intfib[1]=1;
				else intfib[i-1]=intfib[i-2]+intfib[i-3];
				System.out.print(intfib[i-1]+"  ");
			}

		}

}
package Text;

public class sum1 {
	public int sum(int n){

		int x=0;
		for(int i=2;i<=n;i+=2){
			x=x+i;
		}
		int s=x;
		return s;
	}
	public void prient(){
		System.out.println(sum(100));
	}

}