java基礎練習

java基礎

1.基礎輸出

2.基礎判斷

3.基礎循環

4.求斐波那契數列前20項

5.求100以内的質數

package com.company;

import java.util.Scanner;


public class Main {

    public static void main(String[] args) {
	System.out.println("hello world");
	int x=3;
	int y=5;
	System.out.println(x+"+"+y+"="+(x+y));
	System.out.println(x+"-"+y+"="+(x-y));
	System.out.println(x+"/"+y+"="+(x/y));
	System.out.println(x+"/"+y+"="+(x*1.0/y));
	System.out.println(x+"%"+y+"="+(x%y));

	//simple if else
	System.out.println("please enter a int");
	Scanner in = new Scanner(System.in);
	int n =in.nextInt();
	if(n%2==0){
        System.out.println("n is a even number");
    }else{
        System.out.println("n is a odd number");
    }

	//simple switch case
     System.out.println("please enter you score");
	 int score =in.nextInt();
	 switch(score/10){
         case 10:
         case 9: System.out.println("excellent");break;
         case 8:
         case 7:
         case 6: System.out.println("pass");break;
         default: System.out.println("no-pass");break;
     }

//
     int m=6;
	 int c=1;
	 while(m>1){
	     c*=m;
	     m--;
     }
        System.out.println(c);

	 for (int i=1;i<=9;i++){
	     for(int j=1;j<=i;j++){
             System.out.println(i+"*"+j+"="+(x*y)+"\t");;
         }
	     System.out.println();
     }



	 //求斐波那契前20項
        int num[] = new int[20];
        num[0] = 1;
        num[1] = 1;
        System.out.println("斐波那契數列前20項的值如下：");
        System.out.println(num[0]+" ");
        System.out.println(num[1]+" ");
        for(int i=2;i<20;i++){
            num[i]=num[i-1]+num[i-2];
            System.out.println(num[i]+" ");
        }
        System.out.println();

        //求100以内的質數
        boolean j = true;
        for(int a=1;a<100;a++){
            for(int b=2;b<a;b++){
                if(a%b==0)
                    j=false;
            }
            if(j){
                System.out.print(a+"\t");
            }
            j= true;
        }


    }

}