import java.util.Scanner;
public class menology {
    public static void main(String[] args){
        Scanner in=new Scanner(System.in);
        System.out.println("请用户输入年份");
        int year=in.nextInt();
        System.out.println("请用户输入月份");
        int month=in.nextInt();
        int sum=0;
        for(int i=1900;i<year;i++){
            if(year%4==0&&year%100!=0||year%400==0){
                sum+=366;
            }else{
                sum+=365;
            }
        }
        for(int i=1;i<month;i++){
            if(i==2){
                if(year%4==0&&year%100!=0||year%400==0){
                    sum+=29;
                }else{
                    sum+=28;
                }
            }else if(i==4||i==6||i==9||i==11){
                sum+=30;
            }else{
                sum+=31;
            }
        }
        sum+=1;
        int wekday=sum%7;
        System.out.println("日\t一\t二\t三\t四\t五\t六");
        for(int i=1;i<wekday;i++){
            System.out.print("\t");
        }
        if(month==2){
            if(year%4==0&&year%100!=0||year%400==0){
                for(int i=1;i<=29;i++){
                    if(sum%7==6){
                        System.out.print(i+"\n");
                    }else{
                        System.out.print(i+"\t");
                    }
                    sum++;
                }
            }else{
                for(int i=1;i<=28;i++){
                    if(sum%7==6){
                        System.out.print(i+"\n");
                    }else{
                        System.out.print(i+"\t");
                    }
                    sum++;
                }
            }
        }else if(month==4||month==6||month==9||month==11){
            for(int i=1;i<=30;i++){
                if(sum%7==6){
                    System.out.print(i+"\n");
                }else{
                    System.out.print(i+"\t");
                }
                sum++;
            }
        }else{
            for(int i=1;i<=31;i++){
                if(sum%7==6){
                    System.out.print(i+"\n");
                }else{
                    System.out.print(i+"\t");
                }
                sum++;
            }
        }
    }
}

http://blog.

上面的例子能够正常运行，参考一下
Debug或者在关键的计算结果的地方pringln一下吧