/**
* Compares two strings lexicographically.
* The comparison is based on the Unicode value of each character in
* the strings. The character sequence represented by this
* {@code String} object is compared lexicographically to the
* character sequence represented by the argument string. The result is
* a negative integer if this {@code String} object
* lexicographically precedes the argument string. The result is a
* positive integer if this {@code String} object lexicographically
* follows the argument string. The result is zero if the strings
* are equal; {@code compareTo} returns {@code 0} exactly when
* the {@link #equals(Object)} method would return {@code true}.
* <p>
* This is the definition of lexicographic ordering. If two strings are
* different, then either they have different characters at some index
* that is a valid index for both strings, or their lengths are different,
* or both. If they have different characters at one or more index
* positions, let <i>k</i> be the smallest such index; then the string
* whose character at position <i>k</i> has the smaller value, as
* determined by using the < operator, lexicographically precedes the
* other string. In this case, {@code compareTo} returns the
* difference of the two character values at position {@code k} in
* the two string -- that is, the value:
* <blockquote><pre>
* this.charAt(k)-anotherString.charAt(k)
* </pre></blockquote>
* If there is no index position at which they differ, then the shorter
* string lexicographically precedes the longer string. In this case,
* {@code compareTo} returns the difference of the lengths of the
* strings -- that is, the value:
* <blockquote><pre>
* this.length()-anotherString.length()
* </pre></blockquote>
*
* @param anotherString the {@code String} to be compared.
* @return the value {@code 0} if the argument string is equal to
* this string; a value less than {@code 0} if this string
* is lexicographically less than the string argument; and a
* value greater than {@code 0} if this string is
* lexicographically greater than the string argument.
*/
public int compareTo(String anotherString) {
int len1 = value.length;
int len2 = anotherString.value.length;
int lim = Math.min(len1, len2);
char v1[] = value;
char v2[] = anotherString.value;
int k = 0;
while (k < lim) {
char c1 = v1[k];
char c2 = v2[k];
if (c1 != c2) {
return c1 - c2;
}
k++;
}
return len1 - len2;
}
定义字典顺序。这里是如何定义字典顺序。如果两个字符串不同,意味着它们在某个索引处具有不同的字符, 或者它们的长度不同,也或两种都有。如果它们在一个或多个索引处有不同的字符。假设 k 是这类索引的最小值;则在位置 k 上具有较小值的那个字符串(使用 < 运算符确定),其字典顺序在其他字符串之前。在这种情况下,compareTo 返回这两个字符串在位置 k 处两个char 值的差,即值:
https://www.meisen.pro/article/86009ab2ad1a4b93bf9583677cd58f17
注释解释
CompareTo按照字典顺序(lexicographically)比较两个字符串。基于字符串中的每个字符的Unicode值。当前(this)String对象字符序列与给定的参数String字符序列通过字典顺序作比较。如果当前String对象字典顺序大于参数String字典顺序,就返回正整数; 如果当前String对象字段顺序小于参数String字典顺序,就返回负整数;相等(equal(Object))就返回0。
定义字典顺序。这里是如何定义字典顺序。如果两个字符串不同,意味着它们在某个索引处具有不同的字符, 或者它们的长度不同,也或两种都有。如果它们在一个或多个索引处有不同的字符。假设 k 是这类索引的最小值;则在位置 k 上具有较小值的那个字符串(使用 < 运算符确定),其字典顺序在其他字符串之前。在这种情况下,compareTo 返回这两个字符串在位置 k 处两个char 值的差,即值:
如果没有字符不同的索引位置,则较短字符串的字典顺序在较长字符串之前。在这种情况下,k 返回这两个字符串长度的差,即值:
源码