小米我是放弃了，后面都没写，就一直跟第一题钢着，就是不AC

import java.io.IOException;

import java.util.Scanner;

public class Main {

public static void main(String[] args) throws IOException {

int w = 0;

String s = "";

String b = "";

while (true) {

Scanner in = new Scanner(System.in);

String readLine = in.nextLine(); // 获取输入的字符串

char[] a = readLine.toCharArray();

for (int j = 0; j < readLine.length(); j++) {

char i = a[j];

if ((i >= 'A' && i <= 'Z')) {

b = String.valueOf(i);

if (w == 3) {

s = s + b.toUpperCase();

w = 1;

} else {

s = s + "_" + b.toUpperCase();

w = 1;

}

} else if ((i >= 'a' && i <= 'z')) {

b = String.valueOf(i);

if (w == 1) {

s = s + b.toUpperCase();

} else {

s = s + "_" + b.toUpperCase();

w = 1;

}

} else if ((i >= '0' && i <= '9')) {

b = String.valueOf(i);

if (w == 2) {

s = s + b.toUpperCase();

} else {

s = s + "_" + b.toUpperCase();

w = 2;

}

} else if (i == '.') {

s = s + "_";

w = 3;

}

}

System.out.println(s + "_");

s = "";

}

}

}