Why String in Java don’t run in my program

Question

Scanner scan = new Scanner(System.in);
System.out.println("Please Enter the number of the day");
int day = scan.nextInt();
String dayy;

switch(day) {
case 1: dayy("Monday");
break;
case 2: dayy("tuesday");
break;
case 3: dayy("wednesday");
break;
case 4: dayy("thursday");
break;
case 5: dayy("friday");
break;
case 6: dayy("saturday");
break;
case 7: dayy("sunday");
break;
default: dayy("invaild day");
break;

}

System.out.println(dayy);

Answer 1

nouf ibrahim Still there is problem.

Answer 2

okay i knew what is the problem , i missed the equal sign LOL😅