黑色星期五&星期几

 public void blackfriday() {
       int d=13;
     System.out.println("pls input year(4 single number):");
     int y = new Scanner(System.in).nextInt();    
       for(int m=1;m<13;++m){
       if(friday(y,m,d)==1)
       System.out.println("blackFriday: "+m+"月"+d+"日");            
       }
   }
 
int friday(int y,int m,int d){   
   int c=y/100;
   y=y-100*c;
   int w;
   if(m<3){
    m+=12;
   y-=1;
   }
   w=c/4-2*c+y+y/4+13*(m+1)/5+d-1;
   if(w<0) w+=7;
   w%=7;
   if(w==5)
   return 1;
   else return 0;
   }
  }

 

星期几:

  public void weekDay() {
   int w = 0;
   String week[]= {"Sunday:星期日","Monday:星期一","Tuesday:星期二","Wednesday:星期三","Thursday:星期四","Friday:星期五","Saturday:星期六"};
   //System.out.println("pls input year(4 single number):");
   int y = new Scanner(System.in).nextInt();

   //System.out.println("pls input month:");
   int m = new Scanner(System.in).nextInt();
  
   //System.out.println("pls input day:");
   int d = new Scanner(System.in).nextInt();
   int c=y/100;
   y=y-100*c;
   if(m<3){
    m+=12;
    y-=1;
     }        
   w=c/4-2*c+y+y/4+13*(m+1)/5+d-1;    
   if(w<0) w+=7;
   w%=7; //求余
   System.out.println(week[w]);      
      }
  }