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
 """;

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。

当使用一长串的+时，只会创建一个StringBuilder，除非在编译时确定String，在这种情况下不使用StringBuilder !

StringBuilder唯一更高效的情况是使用多个语句构造String。

String a = "a\n";
String b = "b\n";
String c = "c\n";
String d = "d\n";

String abcd = a + b + c + d;
System.out.println(abcd);

String abcd2 = "a\n" +
        "b\n" +
        "c\n" +
        "d\n";
System.out.println(abcd2);

注意:只创建了一个StringBuilder。

  Code:
   0:   ldc     #2; //String a\n
   2:   astore_1
   3:   ldc     #3; //String b\n
   5:   astore_2
   6:   ldc     #4; //String c\n
   8:   astore_3
   9:   ldc     #5; //String d\n
   11:  astore  4
   13:  new     #6; //class java/lang/StringBuilder
   16:  dup
   17:  invokespecial   #7; //Method java/lang/StringBuilder."<init>":()V
   20:  aload_1
   21:  invokevirtual   #8; //Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
   24:  aload_2
   25:  invokevirtual   #8; //Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
   28:  aload_3
   29:  invokevirtual   #8; //Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
   32:  aload   4
   34:  invokevirtual   #8; //Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
   37:  invokevirtual   #9; //Method java/lang/StringBuilder.toString:()Ljava/lang/String;
   40:  astore  5
   42:  getstatic       #10; //Field java/lang/System.out:Ljava/io/PrintStream;
   45:  aload   5
   47:  invokevirtual   #11; //Method java/io/PrintStream.println:(Ljava/lang/String;)V
   50:  ldc     #12; //String a\nb\nc\nd\n
   52:  astore  6
   54:  getstatic       #10; //Field java/lang/System.out:Ljava/io/PrintStream;
   57:  aload   6
   59:  invokevirtual   #11; //Method java/io/PrintStream.println:(Ljava/lang/String;)V
   62:  return

为了进一步澄清我的问题，我根本不关心性能。我关心的是可维护性和设计问题。

尽你所能让它清晰简单。

String.join

Java 8为Java .lang. string添加了一个新的静态方法，它提供了一个更好的选择:

String.join ( CharSequence分隔符， CharSequence进行…元素 ）

使用它:

String s = String.join(
    System.getProperty("line.separator"),
    "First line.",
    "Second line.",
    "The rest.",
    "And the last!"
);

一个不错的选择。

import static some.Util.*;

    public class Java {

        public static void main(String[] args) {

            String sql = $(
              "Select * from java",
              "join some on ",
              "group by"        
            );

            System.out.println(sql);
        }

    }


    public class Util {

        public static String $(String ...sql){
            return String.join(System.getProperty("line.separator"),sql);
        }

    }

一个简单的选择是使用SciTE (http://www.scintilla.org/SciTEDownload.html)这样的编辑器编辑java代码，它允许您对文本进行WRAP，以便容易地查看和编辑长字符串。如果你需要转义字符，你只需输入它们。通过关闭“换行”选项，您可以检查字符串是否仍然是一个很长的单行字符串。当然，如果不是，编译器也会告诉你。

Eclipse或NetBeans是否支持编辑器中的文本包装，我不知道，因为它们有太多的选项。但如果没有，这将是一个很好的补充。