java - 通过按位运算将 Unicode 转换为字符

Question

感谢 this，我知道如何将 Unicode 转换为字符问题，但是当我对 Unicode 进行按位运算时，效果不太好。

.fromCharCode() 是一个 Javascript 函数，用于将 Unicode 转换为字符。我想知道它在 Java 中的等效项，能够将按位运算作为参数处理。

此代码无法编译

public String str2rstr_utf8(String input) {
  String output = "";
  int i = -1;
  int x, y;
  while (++i < input.length()) {
    /* Decode utf-16 surrogate pairs */
    x = Character.codePointAt(input, i);
    y = i + 1 < input.length() ? Character.codePointAt(input, i + 1) : 0;
    if (0xD800 <= x && x <= 0xDBFF && 0xDC00 <= y && y <= 0xDFFF) {
      x = 0x10000 + ((x & 0x03FF) << 10) + (y & 0x03FF);
      i++;
    }
    /* Encode output as utf-8 */
    if (x <= 0x7F) output += String.fromCharCode(x);
    else if (x <= 0x7FF) output += String.fromCharCode(0xC0 | ((x >>> 6) & 0x1F), 0x80 | (x & 0x3F));
    else if (x <= 0xFFFF) output += String.fromCharCode(0xE0 | ((x >>> 12) & 0x0F), 0x80 | ((x >>> 6) & 0x3F), 0x80 | (x & 0x3F));
    else if (x <= 0x1FFFFF) output += String.fromCharCode(0xF0 | ((x >>> 18) & 0x07), 0x80 | ((x >>> 12) & 0x3F), 0x80 | ((x >>> 6) & 0x3F), 0x80 | (x & 0x3F));
  }
  return output;
}

Answer 1

如果我没记错的话，您正在尝试用 UTF-8 编码 Java 字符串。 Java 对其有直接支持:

public byte[] str2rstr_utf8(String str)
{
    return str.getBytes(Charset.forName("UTF-8"));
}