StringBuilder中reverse的疑问
public AbstractStringBuilder reverse() { boolean hasSurrogate = false; int n = count - 1; for (int j = (n-1) >> 1; j >= 0; --j) { char temp = value[j]; char temp2 = value[n - j]; 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 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; }
上面是reverse的源码，其中hasSurrogate表示unicode编码占用一个还是两个字符。
现在想实现：构造一个StringBuilder对象，调用其reverse方法，进行调试，使其满足hasSurrogate 为true
的情况。
尝试使用中文字符，但是无效，比如：os我china，调试时hasSurrogate仍然为false。
求大家指点。
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The code snippet you've provided is a method from Java's AbstractStringBuilder class, which is a part of the Java SDK and not directly related to Alibaba Cloud products or services. However, I can explain what this code does in the context of Java programming.
This reverse() method is intended to reverse the characters within the AbstractStringBuilder instance it's called on. Here's a breakdown of how it works:
-
Initialization: It initializes a boolean variable
hasSurrogateasfalse. Surrogate pairs are used in Java (and Unicode) to represent characters outside the Basic Multilingual Plane (BMP), such as certain emojis or rare characters. Each surrogate pair consists of two char values. -
Count and Loop Setup: It calculates
nas the last index of the internal character array (value) by subtracting 1 from thecountof characters. Then, it sets up a loop that will iterate over the first half of the string, since swapping elements from both ends will cover the entire range. -
Surrogate Pair Check: Inside the loop, it checks for surrogate pairs. If
temp(the current character from the front) ortemp2(the corresponding character from the end) is a high or low surrogate,hasSurrogateis set totrue. This check is crucial because swapping individual surrogates would break the pair and result in invalid characters. -
Character Swap: Although the actual swap operation isn't shown in your snippet, typically after the surrogate check, the code would swap
tempwithtemp2, effectively reversing their positions in the string. -
Loop Completion: The loop continues until all necessary swaps have been made, effectively reversing the entire string content.
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