java计算求某年某月某日是星期几?

可以通过日历中DAY_OF_WEEK 方法进行星期几获取：
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.Calendar;
import java.util.Date;

public class DateTest {

public static void main(String[] args) {
InputStreamReader isr = new InputStreamReader(System.in);
BufferedReader br = new BufferedReader(isr);
String dateStr;
try {
System.out.println("请按照2012-1-1格式输入日期：");
dateStr = br.readLine();
Calendar calendar = Calendar.getInstance();
java.text.SimpleDateFormat formt = new java.text.SimpleDateFormat(
"yyyy-MM-dd");
Date date = formt.parse(dateStr);
calendar.setTime(date);
System.out.println("今天星期" + calendar.get(Calendar.DAY_OF_WEEK + 1));
System.out.println("今天是" + calendar.get(Calendar.YEAR) + "年的第"
+ calendar.get(Calendar.DAY_OF_YEAR) + "天");
} catch (Exception e) {
e.printStackTrace();
}
}
}

import javax.swing.JOptionPane; class nian{ public static void main(String args[]){ int y,m,d,N,s,z,a; y=Integer.parseInt(JOptionPane.showInputDialog("请输入一个年号:")); m=Integer.parseInt(JOptionPane.showInputDialog("请输入月份:")); d=Integer.parseInt(JOptionPane.showInputDialog("请输入日期:")); String s1=y+"年"+m+"月"+d+"日"; for (;m<=2;m+=12,y=y-1);{ z=(y/4)-(y/100)+(y/400); a=3*(m+1)/5; N=d+2*m+a+y+z+1; s=N%7; s1=s1+"是星期"+s; JOptionPane.showMessageDialog(null,s1); } } }