java之Calendar类

public class Demo9_Calendar {

    /*
     * A:Calendar是一个抽象类
     * B：成员方法
     *    public static Calendar getInstance()    
     *    public int get(int field)
     * C:成员方法
     *    public void add(int field, int amount)    对指定的字段进行向前或向后加或减
     *    public final void set(int year, int month, int date)   对指定字段进行修改
     */
    public static void main(String[] args) {

        //demo1();
        Calendar c = Calendar.getInstance();
        c.add(Calendar.MONTH, -1);                   //月份减1
        c.set(Calendar.YEAR, 2088);                  //年份修改为2088
        System.out.println(c.get(Calendar.YEAR) + "年" + getNum(c.get(Calendar.MONTH) + 1) + "月" 
                + getNum(c.get(Calendar.DAY_OF_MONTH)) + "日" + getWeek(c.get(Calendar.DAY_OF_WEEK)));
        
        
    }

    public static void demo1() {
        Calendar c = Calendar.getInstance();     //相当于父类引用指向子类对象
        System.out.println(c.get(Calendar.YEAR));
        System.out.println(c.get(Calendar.MONTH)); //月份是从0开始的
        System.out.println(c.get(Calendar.DAY_OF_MONTH));
        System.out.println(c.get(Calendar.DAY_OF_WEEK)); //周日是第一天
        System.out.println(c.get(Calendar.YEAR) + "年" + getNum(c.get(Calendar.MONTH) + 1) + "月" 
                + getNum(c.get(Calendar.DAY_OF_MONTH)) + "日" + getWeek(c.get(Calendar.DAY_OF_WEEK)));
    }

    /**
     * 将星期存储表中进行查表
     * @param week
     * @return 
     */
    public static String getWeek(int week) {
        String[] arr = {"","星期日","星期一","星期二","星期三","星期四","星期五","星期六"};
        return arr[week];
    }
    
    /**
     * @param num
     * @return String
     */
    public static String getNum(int num) {
        /*if (num < 10) {
            return "0" + num;
        }else {
            return "" + num;
        }*/
        return num > 9 ? "" + num : "0" + num;
    }
}

利用Calendar类计算某一年是否是闰年：

/*
     * 给定一个年份，判断是否是闰年
     * 1.提示键盘输入年份
     * 2.创建Calendar对象
     * 3.通过set方法将日期设置为哪一年的3月1日
     * 4.将日减1
     * 5.判断日是否是29，得到结果
     */
    public static void main(String[] args) {

        Scanner sc = new Scanner(System.in);
        System.out.println("请输入需要判断的年份：");
//        int year = sc.nextInt();
//        System.out.println(getYear(year));
        
        //优化，判断输入是否是4位数字字符串
        int year = 0;
        String s = sc.nextLine();
        String regex = "\d{4}";
        if (s.matches(regex)) {
            year = Integer.parseInt(s);
            System.out.println(getYear(year));
            
        }else {
            System.out.println("输入有误！");
        }
        
    }
    
    public static boolean getYear(int year) {
        Calendar c = Calendar.getInstance();
        c.set(year, 2, 1);
        c.add(Calendar.DAY_OF_MONTH, -1);
        System.out.println(c.get(Calendar.DAY_OF_MONTH));
        return c.get(Calendar.DAY_OF_MONTH) == 29;
    }