HDOJ/HDU 1088 Write a simple HTML Browser(HTML字符串)

Problem Description
If you ever tried to read a html document on a Macintosh, you know how hard it is if no Netscape is installed.
Now, who can forget to install a HTML browser? This is very easy because most of the times you don’t need one on a MAC because there is a Acrobate Reader which is native to MAC. But if you ever need one, what do you do?
Your task is to write a small html-browser. It should only display the content of the input-file and knows only the html commands (tags) <br> which is a linebreak and <hr> which is a horizontal ruler. Then you should treat all tabulators, spaces and newlines as one space and display the resulting text with no more than 80 characters on a line.

Input
The input consists of a text you should display. This text consists of words and HTML tags separated by one or more spaces, tabulators or newlines.
A word is a sequence of letters, numbers and punctuation. For example, “abc,123” is one word, but “abc, 123” are two words, namely “abc,” and “123”. A word is always shorter than 81 characters and does not contain any ‘<’ or ‘>’. All HTML tags are either <br> or <hr>.

Output
You should display the the resulting text using this rules:
. If you read a word in the input and the resulting line does not get longer than 80 chars, print it, else print it on a new line.
. If you read a <br> in the input, start a new line.
. If you read a <hr> in the input, start a new line unless you already are at the beginning of a line, display 80 characters of ‘-’ and start a new line (again).
The last line is ended by a newline character.

Sample Input

Hallo, dies ist eine
ziemlich lange Zeile, die in Html
aber nicht umgebrochen wird.
<br>
Zwei <br> <br> produzieren zwei Newlines.
Es gibt auch noch das tag <hr> was einen Trenner darstellt.
Zwei <hr> <hr> produzieren zwei Horizontal Rulers.
Achtung       mehrere Leerzeichen irritieren

Html genauso wenig wie

mehrere Leerzeilen.

Sample Output

Hallo, dies ist eine ziemlich lange Zeile, die in Html aber nicht umgebrochen
wird.
Zwei

produzieren zwei Newlines. Es gibt auch noch das tag
--------------------------------------------------------------------------------
was einen Trenner darstellt. Zwei
--------------------------------------------------------------------------------
--------------------------------------------------------------------------------
produzieren zwei Horizontal Rulers. Achtung mehrere Leerzeichen irritieren Html
genauso wenig wie mehrere Leerzeilen.

注意点：
（1） 每行最多80个字符，如果加上最后一个单词大于80，则最后一个单词移到下一行。
（2） <hr>如果处于当前行字符数等于0的情况，则直接输出，否则先输出回车，在输出<hr>,只含有<br>和<hr>标签
(3) 文章最后要有一个回车

equals表示的相等，是指向对象的相等；而compareTo的相等，是内容的相等。
不过其中有一个问题，很奇怪~我用equals老是PE，用compareTo就没问题了~~~弄不懂~

代码注释标识了！
有知道原因的大牛，请在评论区指点下，谢啦~
(哈哈~解决啦~其实这2个都可以的~)
之前的PE应该不是这个原因~

import java.util.Scanner;

public class Main{

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        String result = new String("");
        String str;
        while (sc.hasNext()) {
            str = sc.next();
            if ("".equals(str)) {
                continue;
            }
            if ("<br>".equals(str)) {
                System.out.println(result);
                result = "";
            } else if ("<hr>".equals(str)) {
                if (result.compareTo("")!=0) {
                //  if (!"".equals(result)) {//这个是一样的！
                    System.out.println(result);
                }
                gong.print();
                result = "";
            } else {

                String temp = result;
                if ((temp + " " + str).length() < 80) {
                    if (!"".equals(result)) {
                        result += " " + str;
                    } else {
                        result = str;// 每一行的第一个输入
                    }
                } else {
                    System.out.println(result);
                    result = str;
                }
            }
        }
        if (!("".equals(result))) {
            System.out.println(result);
        }
    }
}

class gong {
    static void print() {
        for (int i = 0; i < 80; i++)
            System.out.print("-");
        System.out.println();
    }
}