Java15现在像Python一样支持三引号字符串。

当我读到多行语法确实是为jdk7计划的(在java存在了多少年之后?)时，我有点恼火。有趣的是，甚至还没有readAll()函数用于读取文件的完整内容(仅从jdk7读取，啊啊)，因此下面的代码读取单行。

/*
  MakeMultiline v1.0 (2010) - Free to use and copy.

  Small gadget to turn text blobs into one java string literal
  (doing the split in lines, adding \n at each end and enclosing
  in double quotes). Does escape quotes encountered in the text blob.

  Useful for working around missing multiline string syntax in java
  prior jdk7. Use with:

     java MakeMultiline "    "
  or
     java MakeMultiline "    " mytextfile.txt
*/

import java.io.*;

class MakeMultiline {
  public static void main(String[] args) {
    try {
      // args[0]: indent
      // args[1]: filename to read (optional; stdin if not given)
      // Beware the nmb of newlines at the end when using stdin!

      String indent = (args.length > 0 ? args[0] : "");
      FileReader fr = null; BufferedReader br;
      if (args.length > 1)
        { fr =  new FileReader(args[1]); br = new BufferedReader(fr); }
      else
        { br = new BufferedReader(new InputStreamReader(System.in)); }
      String s; String res = "";
      while((s = br.readLine()) != null) {
        if (res.length() > 0) res += " +\n";
        res += indent + "\"" + s.replace("\"", "\\\"") + "\\n\"";
      }
      br.close(); if (fr != null) fr.close();
      System.out.println(res + ";");
    }
    catch(Exception e) {
      System.out.println("Exception: " + e);
    }
  }
}

这对我来说是最快的解决办法。(2010-01-27)

后期模型JAVA对+和常量字符串进行了优化，在幕后使用了StringBuffer，所以你不想让它使你的代码变得混乱。

它指出了JAVA的一个疏忽，它不像ANSI C在双引号字符串之间只有空白的自动连接，例如:

const char usage = "\n"
"Usage: xxxx <options>\n"
"\n"
"Removes your options as designated by the required parameter <options>,\n"
"which must be one of the following strings:\n"
"  love\n"
"  sex\n"
"  drugs\n"
"  rockandroll\n"
"\n" ;

我想有一个多行字符数组常量，其中嵌入换行是光荣的，所以我可以在没有任何混乱的情况下呈现块，例如:

String Query = "
SELECT
    some_column,
    another column
  FROM
      one_table a
    JOIN
      another_table b
    ON    a.id = b.id
      AND a.role_code = b.role_code
  WHERE a.dept = 'sales'
    AND b.sales_quote > 1000
  Order BY 1, 2
" ;

要做到这一点，需要打败JAVA之神。

使用JDK/12早期访问构建# 12，现在可以在Java中使用多行字符串，如下所示:

String multiLine = `First line
    Second line with indentation
Third line
and so on...`; // the formatting as desired
System.out.println(multiLine);

这将导致以下输出:

第一行 第二行有缩进 第三行 等等……

编辑: 推迟至java 13

JEP 378: Text Blocks涵盖了此功能，并且包含在JDK 15中。它最初出现在JDK 13中的JEP 355: Text Blocks(预览)和JDK 14中的JEP 368: Text Blocks(第二预览)，可以在这些版本中通过——enable-preview javac选项启用。

语法允许这样写:

String s = """
           text
           text
           text
           """;

在此之前，在JDK 12中，JEP 326: Raw String Literals旨在实现类似的功能，但最终被撤回:

请注意:这原本是JDK 12中的预览语言功能，但它已被撤回，并没有出现在JDK 12中。它在JDK 13中被文本块(JEP 355)所取代。

Java 13预览:

Text Blocks Come to Java. Java 13 delivers long-awaited multiline string by Mala Gupta With text blocks, Java 13 is making it easier for you to work with multiline string literals. You no longer need to escape the special characters in string literals or use concatenation operators for values that span multiple lines. Text block is defined using three double quotes (""") as the opening and closing delimiters. The opening delimiter can be followed by zero or more white spaces and a line terminator.

例子:

 String s1 = """
 text
 text
 text
 """;