我什么时候应该使用 Java 的 StringWriter？
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When should I use Java's StringWriter?
提问by MarkusWillson
回答by Jaskey
It is a specialized Writerthat writes characters to a StringBuffer, and then we use method like toString()to get the string result.
它是一种专门的Writer将字符写入 a StringBuffer，然后我们使用 like 方法toString()获取字符串结果的方法。
When StringWriteris used is that you want to write to a string, but the API is expecting a Writeror a Stream. It is a compromised, you use StringWriteronly when you have to, since StringBuffer/StringBuilderto write characters is much more natural and easier,which should be your first choice.
何时StringWriter使用是您想要写入字符串，但 API 需要 aWriter或 a Stream。这是一个折衷的方法，StringWriter只有在必须时才使用，因为StringBuffer/StringBuilder写字符更自然和更容易，这应该是您的首选。
Here is two of a typical good case to use StringWriter
这是两个典型的好用案例 StringWriter
1.Converts the stack trace into String, so that we can log it easily.
1.将堆栈跟踪转换为String，以便我们可以轻松记录它。
StringWriter sw = new StringWriter();//create a StringWriter
PrintWriter pw = new PrintWriter(sw);//create a PrintWriter using this string writer instance
t.printStackTrace(pw);//print the stack trace to the print writer(it wraps the string writer sw)
String s=sw.toString(); // we can now have the stack trace as a string
2.Another case will be when we need to copy from an InputStreamto chars on a Writerso that we can get Stringlater, using Apache commons IOUtils#copy:
2.另一种情况是当我们需要从 aInputStream上的字符复制到 aWriter以便我们String以后可以 使用Apache commons IOUtils#copy 时：
StringWriter writer = new StringWriter();
IOUtils.copy(inputStream, writer, encoding);//copy the stream into the StringWriter
String result = writer.toString();
回答by RossBille
It is used to construct a string char-by-charor string-by-string.
它用于构造字符串char-by-char或string-by-string.
It is similar to StringBuilderbut uses a StringBufferunder the hood. This is preferable when you are working with an API that requires a stream or writer. If you don't have this requirement it should be more efficient to use a StringBuilder(due to the synchronisation overhead of StringBuffer).
它类似于StringBuilder但StringBuffer在引擎盖下使用了一个。当您使用需要流或编写器的 API 时，这是更可取的。如果您没有此要求，则使用 a 应该更有效StringBuilder（由于 的同步开销StringBuffer）。
Of course this only makes sense if you realise that string concatenation (eg.
当然，这只有在您意识到字符串连接（例如
String s = "abc"+"def"; //... (especially when spread throughout a loop)`
is a slow operation (see here).
是一个缓慢的操作（见这里）。
small e.g.
小如
StringWriter writer = new StringWriter();
writer.write('t');
writer.write("his awesome");
String result = writer.toString();
System.out.println(result); //outputs this is awesome
A better example:
一个更好的例子：
String[] strings = /* some array of strings*/
StringWriter writer = new StringWriter();
for(String s : strings){
writer.write(s);
}
String result = writer.toString();
System.out.println(result);
