如何在 Java 中的 UTF-8 和原生字符串之间进行转换？

Question

Just like the picture, I'd like to convert between the encoded UTF-8 String and Native String in Java. Would anyone some suggestions?非常感谢！

ps。 例如，

String a = "这是一个例子,this is a example";
String b = null;
// block A: processing a, and let b = "这是一个例子,this is a example"

How to implement the "block A"?

Answer 1

您可以使用字符集。请参阅文档 here

Charset.forName("UTF-8").encode(text)

---

或

你也可以使用'java.lang.String'的getBytes()方法Class

text.getBytes(Charset.forName("UTF-8"));

文档：

public byte[] getBytes(Charset charset)
Encodes this String into a sequence of bytes using the given charset, storing the result into a new byte array.

This method always replaces malformed-input and unmappable-character sequences with this charset's default replacement byte array. The CharsetEncoder class should be used when more control over the encoding process is required.

Parameters: charset - The Charset to be used to encode the String

Returns: The resultant byte array

Since:
1.6

Answer 2

Apache Commons Lang StringEscapeUtils.unescapeXml(...)就是你想要的。根据原始字符串的来源，HTML 变体之一可能更合适。

这样使用：

String a = "这是一个例子,this is a example";
String b = StringEscapeUtils.unescapeXml(a);
// block A: processing a, and let b = "这是一个例子,this is a example"
System.out.println(a);
System.out.println(b);

输出：

这是一个例子,this is a example
这是一个例子,this is a example

也有转换其他方式的方法。

Answer 3

右边是十六进制数字 HTML 个实体。

现在 apache commons 库有一个 StringEscapeUtils，它可以将 从 转换为 String，但反过来并不明显（= 应该尝试，可能会给出命名实体）。

public static void main(String[] args) throws InterruptedException {
    String a = "这是一个例子,this is a example";
    String b = fromHtmlEntities(a);
    System.out.println(b);
    String a2 = toHtmlEntities(b);
    System.out.println(a2.equals(a));
    System.out.println(a);
    System.out.println(a2);
}

public static String fromHtmlEntities(String s) {
    Pattern numericEntityPattern = Pattern.compile("\&#[Xx]([0-9A-Fa-f]{1,6});");
    Matcher m = numericEntityPattern.matcher(s);
    StringBuffer sb = new StringBuffer();
    while (m.find()) {
        int codePoint = Integer.parseInt(m.group(1), 16);
        String replacement = new String(new int[] { codePoint }, 0, 1);
        m.appendReplacement(sb, replacement);
    }
    m.appendTail(sb);
    return sb.toString();
}

// Uses java 8  
public static String toHtmlEntities(String s) {
    int[] codePoints = s.codePoints().flatMap(
            (cp) -> cp < 128 // ASCII?
            ? IntStream.of(cp)
            : String.format("&#x%X;", cp).codePoints())
        .toArray();
    return new String(codePoints, 0, codePoints.length);
}