Java学习第四天

• 分支语句
  if（）{
  }
  else if（）{
  }
  else

import java.util.Scanner;

public class Test01 {

    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        System.out.println("请输入年份： ");
        System.out.println("请输入月份");
        int year = input.nextInt();
        int month = input.nextInt();
        if (year > 0 && month > 0 && month <= 12){
            int day;
            if (month == 2){
                if(year % 4 == 0 && year % 100 != 0 || year % 400 == 0){
                    day = 29;
                }
                else{
                    day = 28;
                }
            }
            else if (month == 4 | month == 6 | month == 9 | month == 11){
                day = 30;
            }
            else{
                day = 31;
            }
            System.out.println(year + "年" + month + "月" + "有" + day + "天");
        }
        else {
            System.err.println("输入错误");
        }
        input.close();

    }

}

switch(){               // 整数，字符，枚举，字符串
 }
  case 1:
  break;
  case 2:
  break;
  default:
  break;

import java.util.Scanner;

public class Test02 {

    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        System.out.println("请输入月份： ");
        int month = input.nextInt();
        String wordOfMonth;
        switch (month) {
        case 1:
            wordOfMonth = "January";
            break;
        case 2:
            wordOfMonth = "February";
            break;
        case 3:
            wordOfMonth = "March";
            break;
        case 4:
            wordOfMonth = "April";
            break;
        case 5:
            wordOfMonth = "May";
        case 6:
            wordOfMonth = "June";
            break;
        case 7:
            wordOfMonth = "July";
            break;
        case 8:
            wordOfMonth = "August";
            break;
        case 9:
            wordOfMonth = "September";
            break;
        case 10:
            wordOfMonth = "October";
            break;
        case 11:
            wordOfMonth = "November";
            break;
        case 12:
            wordOfMonth = "December";
            break;
            
        default:
            wordOfMonth = "输入错误";
            break;
        }
        System.out.println(wordOfMonth);
        input.close();

    }

}

• 循环语句
  while(){
  }

public class Test05 {

    public static void main(String[] args) {
        int i = 1;
        while(i <= 10){
            System.out.println(i + ". Hello,world!");
            i += 1;
        }
        System.out.println("循环结束");

    }

}

  do{
   }  while();

public class Test07 {

    public static void main(String[] args) {
        int i = 0;
        int sum = 0;
            do {
                i += 1;
                sum += i;
            } while (i < 100);
        System.out.println(sum);
        System.out.println("循环结束");

    }

}