JDK源码学习--AbstractStringBuilder reverse()

public AbstractStringBuilder reverse() {
//是否含代理字符
//高代理highSurrogate和低代理lowSurrogate概念请另查询char与Unicode字符
boolean hasSurrogate = false;
//定义一个变量表示长度-1
int n = count - 1;
//j初始化，长度-2再算术右移一位 j = (count-2)/2
//偶数长度，遍历一半次数，对调替换
//奇数长度，遍历一半-1次数，对调替换，中间值不用替换
for (int j = (n-1) >> 1; j >= 0; --j) {
char temp = value[j];
char temp2 = value[n - j];
//如果无代理
if (!hasSurrogate) {
hasSurrogate = (temp >= Character.MIN_SURROGATE && temp <= Character.MAX_SURROGATE)
|| (temp2 >= Character.MIN_SURROGATE && temp2 <= Character.MAX_SURROGATE);
}
value[j] = temp2;
value[n - j] = temp;
}
if (hasSurrogate) {
// Reverse back all valid surrogate pairs
//反转回所有有效代理对
//高代理+低代理组合表示一个字符
for (int i = 0; i < count - 1; i++) {
char c2 = value[i];
if (Character.isLowSurrogate(c2)) {
char c1 = value[i + 1];
if (Character.isHighSurrogate(c1)) {
value[i++] = c1;
value[i] = c2;
}
}
}
}
return this;
}