Java15现在像Python一样支持三引号字符串。

String newline = System.getProperty ("line.separator");
string1 + newline + string2 + newline + string3

但是，最好的替代方法是使用String.format

String multilineString = String.format("%s\n%s\n%s\n",line1,line2,line3);

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)

注意:这个答案适用于Java 14及以上版本。

Java 15引入了文本块(多行文字)。详情请看这个答案。

听起来像是要做一个多行文字，这在Java中是不存在的。

你最好的选择是用+ d组合的字符串。人们提到的一些其他选项(StringBuilder, String。format, String.join)只有当你从一个字符串数组开始时才更可取。

考虑一下:

String s = "It was the best of times, it was the worst of times,\n"
         + "it was the age of wisdom, it was the age of foolishness,\n"
         + "it was the epoch of belief, it was the epoch of incredulity,\n"
         + "it was the season of Light, it was the season of Darkness,\n"
         + "it was the spring of hope, it was the winter of despair,\n"
         + "we had everything before us, we had nothing before us";

与StringBuilder:

String s = new StringBuilder()
           .append("It was the best of times, it was the worst of times,\n")
           .append("it was the age of wisdom, it was the age of foolishness,\n")
           .append("it was the epoch of belief, it was the epoch of incredulity,\n")
           .append("it was the season of Light, it was the season of Darkness,\n")
           .append("it was the spring of hope, it was the winter of despair,\n")
           .append("we had everything before us, we had nothing before us")
           .toString();

与String.format ():

String s = String.format("%s\n%s\n%s\n%s\n%s\n%s"
         , "It was the best of times, it was the worst of times,"
         , "it was the age of wisdom, it was the age of foolishness,"
         , "it was the epoch of belief, it was the epoch of incredulity,"
         , "it was the season of Light, it was the season of Darkness,"
         , "it was the spring of hope, it was the winter of despair,"
         , "we had everything before us, we had nothing before us"
);

相对于Java8 String.join():

String s = String.join("\n"
         , "It was the best of times, it was the worst of times,"
         , "it was the age of wisdom, it was the age of foolishness,"
         , "it was the epoch of belief, it was the epoch of incredulity,"
         , "it was the season of Light, it was the season of Darkness,"
         , "it was the spring of hope, it was the winter of despair,"
         , "we had everything before us, we had nothing before us"
);

如果您想在特定的系统中使用换行符，您要么需要使用system . lineseparator()，要么可以在String.format中使用%n。

另一种选择是将资源放在文本文件中，只读取该文件的内容。对于非常大的字符串，这将是可取的，以避免不必要地膨胀您的类文件。

从问题中还不完全清楚作者是否有兴趣处理某种需要有一些动态值的格式化大字符串，但如果是这种情况，像StringTemplate (http://www.stringtemplate.org/)这样的模板引擎可能非常有用。

下面是一个使用StringTemplate的简单代码示例。实际的模板("Hello， < name >")可以从外部纯文本文件加载。模板中的所有缩进都将被保留，不需要转义。

import org.stringtemplate.v4.*;
 
public class Hello {
    public static void main(String[] args) {
        ST hello = new ST("Hello, <name>");
        hello.add("name", "World");
        System.out.println(hello.render());
    }
}

附注:为了可读性和本地化目的，从源代码中删除大块文本总是一个好主意。

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
 """;