java 输入年、月份，输出本月日历表

请读者先学习Date类与Calendar类！

import java.util.Calendar;import javax.management.StringValueExp;public class CalendarBean {int year ;int month;int day;public void setTime(int year ,int month) { //用于确定年月日this.year=year;this.month=month;if((month==1)||(month==3)||(month==5)||(month==7)||(month==8)||(month==10)||(month==12)) {this.day=31;}if((month==4)||(month==6)||(month==9)||(month==11)) {this.day=30;}if(month==2) {//闰年判断if((year%400==0)||(year%4==0)&&(year%100!=0)) {this.day=29;}elseday=28;}}public String [] getCalendar() {Calendar ca =Calendar.getInstance();ca.set(year, month-1,1);//注意month-1String a[]=new String[42];int weekenday=ca.get(Calendar.DAY_OF_WEEK);//获取本月一号对应的周几for(int i =0;i<weekenday;i++) {a[i]=" ";}for(int i =weekenday,n=1;i<weekenday+day;i++) {a[i]=String.valueOf(n);n++;}for(int i = weekenday+day;i<a.length;i++) {a[i]=" ";}return a;}}public class Mian {public static void main(String[] args) {CalendarBean c=new CalendarBean();c.setTime(2021, 6);String a[]=c.getCalendar();char str[]= "日一二三四五六".toCharArray();for(int i =0;i<str.length;i++) {System.out.printf("%4c",str[i]);}for(int i =0;i<a.length;i++) {if(i%7==0)//每七天就要换行System.out.println("");System.out.printf("%4s",a[i]);}}}

存在问题：没有对齐，欢迎留言指正！