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)

使用这个库

https://github.com/alessio-santacroce/multiline-string-literals

可以这样写

System.out.println(newString(/*
      Wow, we finally have
      multiline strings in
      Java! HOOO!
*/));

很好很简单，但是只适用于单元测试

这个问题有两个答案:

In you want to stick to pure Java, with Java 14 being released in March 2020, you can leverage the JEP 368 - Text Blocks, in Second Preview mode. Actually the feature is in preview mode in other releases (at least 13 has it). I created and example set here. While this feature is useful, it can be easily abused. Remember that Java requires compilation - having large character arrays in your code can be an easy way to shoot yourself in the leg (if you want a quick change, you will need recompilation - that toolset might not be available to the guy operating your application).

根据我的经验，建议在配置文件中保留大字符串(通常是应用程序操作员可以/应该在运行时更改的字符串)。

总结:负责地使用文本块:)。

加号被转换为StringBuilder。除非两个字符串都是常量，以便编译器可以在编译时将它们组合在一起。至少，Sun的编译器是这样的，我怀疑大多数(如果不是所有)其他编译器也会这样做。

So:

String a="Hello";
String b="Goodbye";
String c=a+b;

通常生成完全相同的代码:

String a="Hello";
String b="Goodbye":
StringBuilder temp=new StringBuilder();
temp.append(a).append(b);
String c=temp.toString();

另一方面:

String c="Hello"+"Goodbye";

等于:

String c="HelloGoodbye";

也就是说，为了可读性，在多行中使用加号将字符串字面量分开并不会受到惩罚。

你可以使用scala-code，它与java兼容，并且允许用""" "括起来的多行字符串:

package foobar
object SWrap {
  def bar = """John said: "This is
  a test
  a bloody test,
  my dear." and closed the door.""" 
}

(注意字符串内的引号)和来自java:

String s2 = foobar.SWrap.bar ();

这样是否更舒服?

另一种方法，如果你经常处理长文本，应该放在你的源代码中，可能是一个脚本，它从外部文件中获取文本，并将其包装为一个多行java- string，像这样:

sed '1s/^/String s = \"/;2,$s/^/\t+ "/;2,$s/$/"/' file > file.java

这样你就可以很容易地复制粘贴到你的源代码中。

在IntelliJ IDE中，你只需要输入:

""

然后将光标放置在引号内并粘贴字符串。IDE将它扩展为多个连接的行。