你可以在一个单独的方法中连接你的追加:

public static String multilineString(String... lines){
   StringBuilder sb = new StringBuilder();
   for(String s : lines){
     sb.append(s);
     sb.append ('\n');
   }
   return sb.toString();
}

无论哪种方式，都更喜欢StringBuilder而不是加号符号。

我有时使用一个并行groovy类来充当一个字符串包

这里的java类

public class Test {
    public static void main(String[] args) {
        System.out.println(TestStrings.json1);
        // consume .. parse json
    }
}

以及TestStrings.groovy中令人垂涎的多行字符串

class TestStrings {
    public static String json1 = """
    {
        "name": "Fakeer's Json",
        "age":100,
        "messages":["msg 1","msg 2","msg 3"]
    }""";
}

当然，这只适用于静态字符串。如果我必须在文本中插入变量，我会将整个文件更改为groovy。只要保持强类型实践，它就可以实现。

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);

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。

一个小技巧。使用这个，我在动态创建的HTML页面中注入javascript

StringBuilder builder = new StringBuilder();

public String getString()
{
    return builder.toString();
}
private DropdownContent _(String a)
{
    builder.append(a);
    return this;
}

public String funct_showhide()
{
   return
    _("function slidedown_showHide(boxId)").
    _("{").
    _("if(!slidedown_direction[boxId])slidedown_direction[boxId] = 1;").
    _("if(!slideDownInitHeight[boxId])slideDownInitHeight[boxId] = 0;").
    _("if(slideDownInitHeight[boxId]==0)slidedown_direction[boxId]=slidedownSpeed; ").
    _("else slidedown_direction[boxId] = slidedownSpeed*-1;").
    _("slidedownContentBox = document.getElementById(boxId);").
    _("var subDivs = slidedownContentBox.getElementsByTagName('DIV');").
    _("for(var no=0;no<subDivs.length;no++){").
    _(" if(subDivs[no].className=='dhtmlgoodies_content')slidedownContent = subDivs[no];").
    _("}").
    _("contentHeight = slidedownContent.offsetHeight;").
    _("slidedownContentBox.style.visibility='visible';").
    _("slidedownActive = true;").
    _("slidedown_showHide_start(slidedownContentBox,slidedownContent);").
    _("}").getString();

}