《重构：改善既有代码的设计》——关于代码注释的唠叨

　　这几天在看《重构：改善既有代码的设计》英文评注版这本书，以前简单看过这本书，但并不是看的特别深入。经过了一段时间的“磨练”，现在回来重新看这本书，又很多想法。

　　首先，这本书是一本好书，我感觉是软件工程师必看的一本书，而且如果有大量的编码经验看这本书会收获很大。这本书主要内容是代码重构。

　　在书中第3章中有这样一段话是用来描述代码注释的：

　　A good time to use a comment is when you don't know what to do. In addition to describe what is going on,comments can indicate areas in which you aren't  sure. A comments is a good place to say why you did something. 

　　书中的中文评注如下：

　　高明的程序员绝对不会将注释作为说明代码的重要手段。注释就像咖啡，适量饮用可以提精神，一旦过量，就变得过度亢奋了。

　　我个人感觉上面两端话言简意赅的说出了注释的作用，注释只是代码的一个辅助，是为了我们更好的理解代码。其实关于代码风格和注释风格，每个人都有自己的看法。我觉得都没有错，只不过每个人的看法不一样。就像我，我个人认为代码首先是给程序员看的，其次是给机器看的。因为，发明高级程序语言的目的之一就是为了让人们更好的阅读代码。变量和方法的命名就可以说明变量的作用，如果说不清楚，可以使用注释。但如果是简单易懂的变量，我觉得写注释没必要。

1 string personName;    // 人员姓名

　　就像上面的一行代码，我认为没必要写这个注释，不要因为写注释而去写注释。此外，在最近阅读Java源代码的时候，我发现Java源代码注释有很多特点。

 1     /**
 2      * Compares two strings lexicographically.
 3      * The comparison is based on the Unicode value of each character in
 4      * the strings. The character sequence represented by this
 5      * {@code String} object is compared lexicographically to the
 6      * character sequence represented by the argument string. The result is
 7      * a negative integer if this {@code String} object
 8      * lexicographically precedes the argument string. The result is a
 9      * positive integer if this {@code String} object lexicographically
10      * follows the argument string. The result is zero if the strings
11      * are equal; {@code compareTo} returns {@code 0} exactly when
12      * the {@link #equals(Object)} method would return {@code true}.
13      * 

14      * This is the definition of lexicographic ordering. If two strings are
15      * different, then either they have different characters at some index
16      * that is a valid index for both strings, or their lengths are different,
17      * or both. If they have different characters at one or more index
18      * positions, let k be the smallest such index; then the string
19      * whose character at position k has the smaller value, as
20      * determined by using the < operator, lexicographically precedes the
21      * other string. In this case, {@code compareTo} returns the
22      * difference of the two character values at position {@code k} in
23      * the two string -- that is, the value:
24      * 
25      * this.charAt(k)-anotherString.charAt(k)
26      * 
27      * If there is no index position at which they differ, then the shorter
28      * string lexicographically precedes the longer string. In this case,
29      * {@code compareTo} returns the difference of the lengths of the
30      * strings -- that is, the value:
31      * 
32      * this.length()-anotherString.length()
33      * 
34      *
35      * @param   anotherString   the {@code String} to be compared.
36      * @return  the value {@code 0} if the argument string is equal to
37      *          this string; a value less than {@code 0} if this string
38      *          is lexicographically less than the string argument; and a
39      *          value greater than {@code 0} if this string is
40      *          lexicographically greater than the string argument.
41      */
42     public int compareTo(String anotherString) {
43         int len1 = value.length;
44         int len2 = anotherString.value.length;
45         int lim = Math.min(len1, len2);
46         char v1[] = value;
47         char v2[] = anotherString.value;
48 
49         int k = 0;
50         while (k < lim) {
51             char c1 = v1[k];
52             char c2 = v2[k];
53             if (c1 != c2) {
54                 return c1 - c2;
55             }
56             k++;
57         }
58         return len1 - len2;
59     }

　　这是String类型的compareTo()函数的源代码，注释比较多，但注释比较集中，并没有影响了代码的阅读。我觉得把一些说明性的注释写在文件、类和函数的开头，这样不仅有助于阅读代码，也不会喧宾夺主。其次Java源代码的变量命名非常优美，值得我去学习。

　　这就是我对注释的一些唠叨。