Java 如何从用户那里获取 StringBuilder
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/18087951/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
How to get StringBuilder From user
提问by gandalf
how can i get StringBuilderfrom users through Scannerclass??
or any other classes?
i know that we can get a string and then put it in a StringBuilderlike this:
我如何StringBuilder通过Scanner课堂从用户那里获得？或任何其他课程？我知道我们可以得到一个字符串，然后StringBuilder像这样把它放进去：
import java.util.Scanner;
public class Sade {
public static void main(String[] args) {
Scanner scan = new Scanner(System.in);
String str;
str = scan.nextLine();
StringBuilder strb = new StringBuilder(str);
}
}
or through using append().
but is there anyway to get StringBuilderdirectly from user??
或通过使用append(). 但无论如何可以StringBuilder直接从用户那里获得？
采纳答案by ddavison
You cannot fetch a StringBuilderobject from the Standard Input, but you can output to the user enter the strings (type 'exit' to exit):and formulate your own.
您无法StringBuilder从标准输入中获取对象，但您可以输出给用户enter the strings (type 'exit' to exit):并制定您自己的内容。
Loop through this until they type 'exit', and each time you fetch the string, you can do myStringBuilder.add(theirInput)
(this, of course, is pseudo-code)
循环遍历直到他们输入“exit”，每次获取字符串时，您都可以这样做myStringBuilder.add(theirInput)
（这当然是伪代码）
回答by Mike Thomsen
You misunderstand the purpose of StringBuilder. String concatenation requires creating a new Stringwhich causes unnecessary garbage collection. StringBuilderappends multiple strings together by putting their contents in a character buffer and then returning a new string all at once. This causes a lot of garbage collection:
你误解了 的目的StringBuilder。字符串连接需要创建一个新的String，这会导致不必要的垃圾回收。StringBuilder通过将多个字符串的内容放入字符缓冲区，然后一次返回一个新字符串，将多个字符串附加在一起。这会导致大量垃圾收集：
while ( (line = scanner.nextLine()) != null)
dataSoFar += line;
Each iteration through that causes the old String object referenced by dataSoFarto be concatenated into a new Stringwith line. StringBuildermerely reads lineand puts its characters onto the end of the internal buffer. When it needs to, it'll resize the buffer which requires a lot less GC work when reading a big source of character data.
每次迭代都会导致引用的旧 String 对象dataSoFar连接成一个新的Stringwith line。StringBuilder只是读取line并将其字符放在内部缓冲区的末尾。当需要时，它会调整缓冲区的大小，这在读取大量字符数据时需要更少的 GC 工作。
Java's API doesn't return you a string builder because it would make no sense here.
Java 的 API 不会返回一个字符串生成器，因为它在这里没有意义。
回答by John Snow
You misunderstand the StringBuilderClass.The principal operations of a StringBuilder are the append and insert methods, which are overloaded so as to accept data of any type. Each effectively converts a given datum to a string and then appends or inserts the characters of that string to the string builder. The append method always adds these characters at the end of the builder; the insert method adds the characters at a specified point. The best thing you can do with your code is :-
你误解了StringBuilder 类。StringBuilder 的主要操作是 append 和 insert 方法，它们被重载以接受任何类型的数据。每个都有效地将给定的数据转换为字符串，然后将该字符串的字符附加或插入到字符串构建器中。append 方法总是在构建器的末尾添加这些字符；insert 方法在指定点添加字符。你可以用你的代码做的最好的事情是：-
import java.util.Scanner;
public class sb {
public static void main(String[] args) {
Scanner scan = new Scanner(System.in);
StringBuilder strb = new StringBuilder(scan.nextLine());
strb.append( scan.nextLine());
System.out.println(strb);
}
}
Ofcourse,it is the same as you posted!
当然和你发的一样！
回答by ja_mesa
If what you want is to read all lines type in by the user into a StringBuilder this can be accomplished with something like this:
如果您想要将用户输入的所有行读取到 StringBuilder 中，则可以通过以下方式完成：
Scanner scan = new Scanner(System.in);
StringBuilder sb = new StringBuilder();
String text=null;
while ((text = scan.nextLine ()) != null)
{
sb.append(text);
}
