加入用分隔符字符串 [英] Join a string using delimiters

问题描述

什么是加入的字符串成一个组合分隔字符串列表的最佳方式。我主要关心的何时停止添加分隔符。我将使用C＃我的例子，但我想这是语言无关的。

What is the best way to join a list of strings into a combined delimited string. I'm mainly concerned about when to stop adding the delimiter. I'll use C# for my examples but I would like this to be language agnostic.

编辑：我还没有使用StringBuilder的做code稍微简单

I have not used StringBuilder to make the code slightly simpler.

使用for循环

for(int i=0; i < list.Length; i++)
{
    result += list[i];
    if(i != list.Length - 1)
        result += delimiter;
}

使用for循环设置的第一个项目previously

result = list[0];
for(int i = 1; i < list.Length; i++)
    result += delimiter + list[i];

这些不会为一个IEnumerable工作，你不知道列表的长度事先让

These won't work for an IEnumerable where you don't know the length of the list beforehand so

使用foreach循环

bool first = true;
foreach(string item in list)
{
    if(!first)
        result += delimiter;
    result += item;
    first = false;
}

在foreach循环变化

这是乔恩的解决方案

StringBuilder builder = new StringBuilder();
string delimiter = "";
foreach (string item in list)
{
    builder.Append(delimiter);
    builder.Append(item);
    delimiter = ",";       
}
return builder.ToString();

使用迭代器

再次

using (IEnumerator<string> iterator = list.GetEnumerator())
{
    if (!iterator.MoveNext())
        return "";
    StringBuilder builder = new StringBuilder(iterator.Current);
    while (iterator.MoveNext())
    {
        builder.Append(delimiter);
        builder.Append(iterator.Current);
    }
    return builder.ToString();
}

还有什么其他的算法有哪些？

What other algorithms are there?

推荐答案

这是不可能在这里得到真正的语言无关的答案，不同的语言和平台处理字符串方式不同，提供不同级别的内置支持加盟名单字符串。你可以采取pretty的多的一样的code两种不同的语言，这将是伟大的一个，可怕的另一回事。

It's impossible to give a truly language-agnostic answer here as different languages and platforms handle strings differently, and provide different levels of built-in support for joining lists of strings. You could take pretty much identical code in two different languages, and it would be great in one and awful in another.

在C＃中，你可以使用：

In C#, you could use:

StringBuilder builder = new StringBuilder();
string delimiter = "";
foreach (string item in list)
{
    builder.Append(delimiter);
    builder.Append(item);
    delimiter = ",";       
}
return builder.ToString();

这会的 prePEND 的所有逗号，但第一个项目。类似code将是很好的在Java中了。

This will prepend a comma on all but the first item. Similar code would be good in Java too.

编辑：下面是一个另类，有点像伊恩后来的回答，但工作在一般的IEnumerable＆LT;字符串＆GT;

Here's an alternative, a bit like Ian's later answer but working on a general IEnumerable<string>.

// Change to IEnumerator for the non-generic IEnumerable
using (IEnumerator<string> iterator = list.GetEnumerator())
{
    if (!iterator.MoveNext())
    {
        return "";
    }
    StringBuilder builder = new StringBuilder(iterator.Current);
    while (iterator.MoveNext())
    {
        builder.Append(delimiter);
        builder.Append(iterator.Current);
    }
    return builder.ToString();
}

在原来的答案编辑近5年后...

EDIT nearly 5 years after the original answer...

在.NET 4中，<一个href="http://msdn.microsoft.com/en-us/library/system.string.join%28v=vs.100%29.aspx"><$c$c>string.Join是显著超载pretty的。有过载服用的IEnumerable＆LT; T＆GT; 它会自动调用的ToString ，并有一个过载 IEnumerable的＆LT;字符串＆GT; 。所以，你不需要code以上任何更多......对于.NET，反正。

In .NET 4, string.Join was overloaded pretty significantly. There's an overload taking IEnumerable<T> which automatically calls ToString, and there's an overload for IEnumerable<string>. So you don't need the code above any more... for .NET, anyway.

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