java请输入星期几的第一个字母来判断一下是星期几，如果第一个字母一样，则继续 判断第二个字母.代码

答案如下：

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        String day = scanner.nextLine();
        char firstLetter = Character.toLowerCase(day.charAt(0));
        char secondLetter = Character.toLowerCase(day.charAt(1));

        String daysOfWeek = "uomtwrf";
        int index = daysOfWeek.indexOf(firstLetter);
        if (index < 0) {
            System.out.println("Invalid input!");
            return;
        }

        String[] dayNames = {"Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"};
        String result = dayNames[index];
        if (firstLetter == 't') {
            result = secondLetter == 'u' ? "Tuesday" : "Thursday";
        } else if (firstLetter == 's') {
            result = secondLetter == 'a' ? "Saturday" : "Sunday";
        }

        System.out.println("The day of week is " + result);
    }
}

该代码可以读取用户输入的字符串，判断第一个字母是否是星期几的首字母，并根据情况继续判断第二个字母。如果输入无效，则输出错误信息。最终输出判断结果，即星期几的完整名称。