来自Perl，我肯定错过了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。
有什么更好的选择吗?在属性文件中定义我的字符串?
编辑:有两个答案说StringBuilder.append()比加号更可取。谁能详细解释一下他们为什么这么想?在我看来，这一点也不可取。我正在寻找一种方法来解决多行字符串不是一级语言结构这一事实，这意味着我绝对不想用方法调用取代一级语言结构(字符串连接与加号)。
编辑: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。
当前回答
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。
其他回答
import org.apache.commons.lang3.StringUtils;
String multiline = StringUtils.join(new String[] {
"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",
}, "\n");
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JDK/12早期访问构建# 12，现在可以在Java中使用多行字符串，如下所示:
String multiLine = `First line
Second line with indentation
Third line
and so on...`; // the formatting as desired
System.out.println(multiLine);
这将导致以下输出:
第一行 第二行有缩进 第三行 等等……
编辑: 推迟至java 13
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。
参见Java Stringfier。如果需要，将文本转换为StringBuilder java块转义。
