1. Overview

1.概述

In the world of software development, sometimes we might need to convert a string with Unicode encoding into a readable string of letters. This transformation can be useful when working with data from various sources.

在软件开发领域，有时我们可能需要将 Unicode 编码的字符串转换为可读的字母字符串。这种转换在处理来自不同来源的数据时非常有用。

In this article, we’ll explore how to convert a string with Unicode encoding to a string of letters in Java.

本文将探讨如何在 Java 中将 Unicode 编码字符串转换为字母字符串。

2. Understanding Unicode Encoding

2.了解 Unicode 编码

Firstly, Unicode is a universal character encoding standard that assigns a unique number (code point) to every character, no matter the platform or program. Unicode encoding represents characters as escape sequences in the form of “\uXXXX,” where XXXX is a hexadecimal number representing the character’s Unicode code point.

首先，Unicode 是一种通用字符编码标准，无论平台或程序如何，它都会为每个字符分配一个唯一的数字（码位）。Unicode 编码以 “\uXXXX,” 的形式将字符表示为转义序列，其中 XXXX 是十六进制数，代表字符的 Unicode 代码点。

For example, the string “\u0048\u0065\u006C\u006C\u006F World” is encoded with Unicode escape sequences and represents the phrase “Hello World”.

例如，字符串 “\u0048\u0065\u006C\u006C\u006F World” 使用 Unicode 转义序列编码，代表短语 “Hello World” 。

3. Using Apache Commons Text

3.使用 Apache Commons 文本

Apache Commons Text library provides a reliable utility class: StringEscapeUtils, that offers the unescapeJava() method for decoding Unicode escape sequences in a string:

Apache Commons Text 库提供了一个可靠的实用程序类：StringEscapeUtils 提供了 unescapeJava() 方法，用于解码字符串中的 Unicode 转义序列：

String encodedString = "\\u0048\\u0065\\u006C\\u006C\\u006F World";
String expectedDecodedString = "Hello World";
assertEquals(expectedDecodedString, StringEscapeUtils.unescapeJava(encodedString));

4. Using Plain Java

4.使用普通 Java

In addition, we can use the Pattern and Matcher classes from the java.util.regex package to find all Unicode escape sequences in the input string. Then, we can replace each Unicode escape sequence:

此外，我们还可以使用 java.util.regex 包中的 Pattern 和 Matcher 类查找输入字符串中的所有 Unicode 转义序列。然后，我们可以替换每个 Unicode 转义序列：

public static String decodeWithPlainJava(String input) {
    Pattern pattern = Pattern.compile("\\\\u[0-9a-fA-F]{4}");
    Matcher matcher = pattern.matcher(input);

    StringBuilder decodedString = new StringBuilder();

    while (matcher.find()) {
        String unicodeSequence = matcher.group();
        char unicodeChar = (char) Integer.parseInt(unicodeSequence.substring(2), 16);
        matcher.appendReplacement(decodedString, Character.toString(unicodeChar));
    }

    matcher.appendTail(decodedString);
    return decodedString.toString();
}

The regular expression can be interpreted as follows:

正则表达式的解释如下

\\\\u: Match the literal characters “\u”.
[0-9a-fA-F]: Match any valid hexadecimal digit.
{4}: Match exactly four hexadecimal digits in a row.

For example, let’s decode the following string:

例如，让我们对下面的字符串进行解码：

String encodedString = "Hello \\u0057\\u006F\\u0072\\u006C\\u0064";
String expectedDecodedString = "Hello World";
assertEquals(expectedDecodedString, decodeWithPlainJava(encodedString));

5. Conclusion

5.结论

In this tutorial, we’ve explored two ways to convert a string with Unicode encoding to a string of letters in Java.

在本教程中，我们探讨了在 Java 中将 Unicode 编码字符串转换为字母字符串的两种方法。

The example code from this article can be found over on GitHub.

本文的示例代码可在 GitHub 上找到。