Java 支持多行字符串吗？

来自 Perl，我肯定缺少在源代码中创建多行字符串的“here-document”方法：

$string = <<"EOF"  # create a three-line string
text
text
text
EOF

在 Java 中，当我从头开始连接多行字符串时，我必须在每一行上使用繁琐的引号和加号。

有哪些更好的选择？在属性文件中定义我的字符串？

Edit：两个答案都说 StringBuilder.append() 比加号更好。谁能详细解释一下他们为什么这么认为？对我来说，它看起来一点也不更好。我正在寻找一种方法来解决多行字符串不是一流语言构造这一事实，这意味着我绝对不想用方法调用替换一流语言构造（带加号的字符串连接）。

Edit：为了进一步澄清我的问题，我根本不关心性能。我担心可维护性和设计问题。

NOTE：这个答案适用于 Java 14 及更早版本。

Java 15 中引入了文本块（多行文字）。请参阅这个答案 https://stackoverflow.com/a/50155171/466862了解详情。

听起来你想要做一个多行文字，这在 Java 中不存在。

你最好的选择是字符串+就在一起了人们提到的其他一些选项（StringBuilder、String.format、String.join）只有在您从字符串数组开始时才会更好。

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";

Versus 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();

Versus 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"
);

与 Java8 对比String.join() http://docs.oracle.com/javase/8/docs/api/java/lang/String.html#join-java.lang.CharSequence-java.lang.CharSequence...-:

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"
);

如果您想要特定系统的换行符，您需要使用System.lineSeparator()，或者你可以使用%n in String.format.

另一种选择是将资源放入文本文件中，然后只读取该文件的内容。这对于非常大的字符串来说是更可取的，以避免不必要地使类文件膨胀。