java learning

public class Demo
{public static void main(String[] args){for(int i = 1988; i< 2019; i++) {if ((i%4==0 && i%100 != 0) || i%400 ==0) {System.out.println(i);}}}
}public class Demo1
{public static void main(String[] args){for(int i = 1; i <= 5; i++) {for(int j = 1; j <= i; j++) {System.out.print("@");}System.out.println();}}
}public class Demo2
{public static void main(String[] args){int[] arr = {79, 89}; // 数组用花括号， 数组定义 int[]double sum = 0;for (int i = 0; i < arr.length; i++) {sum += arr[i];}double avg = sum/arr.length;System.out.println(avg);}
}public class Demo2
{public static void main(String[] args){int[] arr = new int[6]; // 定义Scanner sc = new Scanner(System.in); // 定义 Scannerfor (int x = 0; x < arr.length; x++) {arr[x] = sc.nextInt(); // 获取下一个
        }int max = getMax(arr);int min = getMin(arr);int sum = getSum(arr);int avg = (sum - min - max)/(arr.length -2);System.out.println(avg);}public static int getSum(int[] arr){int sum = 0;for (int i=0; i<arr.length; i++) {sum += arr[i];}return sum;}public static int getMin(int[] arr){int min = arr[0];for (int = 1; i<arr.length; i++){if (min < arr[i]) {min = arr[i];}}return min;}
}public class Demo2
{public static void main(String[] args){Scanner sc = new Scanner(System.in); // 定义 Scannerint week = sc.nextInt();if (week < 1 || week > 7) {System.out.println();} else if () {}switch (week) {case 1:break;case 2;break;default:System.out.println("xx");}}
}