blocks|key|1157478|text|使用Java+8，您可以以一种非常干净的方式做到这一点：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1157479|String.join(delimiter,+elements);|code-block|syntax|javascript|1157480|它有三种工作方式：|1157481|1)直接指定元素|1157482|String+joined1+=+String.join(",",+"a",+"b",+"c");|1157483|2)使用数组|1157484|String[]+array+=+new+String[]+{+"a",+"b",+"c"+};
String+joined2+=+String.join(",",+array);|1157485|3)使用迭代器|1157486|List<String>+list+=+Arrays.asList(array);
String+joined3+=+String.join(",",+list);|1157487|entityMap^0|0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|W|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|X|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Y|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|Z|8|@]|9|@]|A|$]]|$1|K|3|L|5|D|7|10|8|@]|9|@]|A|$E|F]]|$1|M|3|N|5|6|7|11|8|@]|9|@]|A|$]]|$1|O|3|P|5|D|7|12|8|@]|9|@]|A|$E|F]]|$1|Q|3|R|5|6|7|13|8|@]|9|@]|A|$]]|$1|S|3|T|5|D|7|14|8|@]|9|@]|A|$E|F]]|$1|U|3|-4|5|6|7|15|8|@]|9|@]|A|$]]]|V|$]]

Using Java 8 you can do this in a very clean way:

<pre><code>String.join(delimiter, elements);
</code></pre>

This works in three ways:

1) directly specifying the elements

<pre><code>String joined1 = String.join(",", "a", "b", "c");
</code></pre>

2) using arrays

<pre><code>String[] array = new String[] { "a", "b", "c" };
String joined2 = String.join(",", array);
</code></pre>

3) using iterables

<pre><code>List&lt;String&gt; list = Arrays.asList(array);
String joined3 = String.join(",", list);
</code></pre>

blocks|key|1372492|text|如果你使用的是安卓系统，你可以通过TextUtils.join(delimiter,+tokens)|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1372493|entityMap|0|LINK|mutability|MUTABLE|url|http://developer.android.com/reference/android/text/TextUtils.html#join%2528java.lang.CharSequence,%2520java.lang.Object[]%2529^0|H|X|H|X|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@$9|O|A|P|B|C]]|D|@$9|Q|A|R|1|S]]|E|$]]|$1|F|3|-4|5|6|7|T|8|@]|D|@]|E|$]]]|G|$H|$5|I|J|K|E|$L|M]]]]

If you're on Android you can <a href="http://developer.android.com/reference/android/text/TextUtils.html#join%28java.lang.CharSequence,%20java.lang.Object[]%29"><code>TextUtils.join(delimiter, tokens)</code></a>

blocks|key|1157066|text|对于这个特殊的问题，我更喜欢Guava而不是Apache+StringUtils：|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1157067|Joiner.on(separator).join(array)|code-block|syntax|javascript|1157068|与StringUtils相比，Joiner+API具有流畅的设计和更多的灵活性，例如，null元素可以跳过或替换为占位符。此外，Joiner还提供了一个连接映射的功能，在键和值之间使用分隔符。|style|CODE|1157069|entityMap|0|LINK|mutability|MUTABLE|url|https://guava.dev/releases/16.0/api/docs/com/google/common/base/Joiner.html^0|E|5|0|0|0|17|4|1S|6|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@$A|V|B|W|1|X]]|C|$]]|$1|D|3|E|5|F|7|Y|8|@]|9|@]|C|$G|H]]|$1|I|3|J|5|6|7|Z|8|@$A|10|B|11|K|L]|$A|12|B|13|K|L]]|9|@]|C|$]]|$1|M|3|-4|5|6|7|14|8|@]|9|@]|C|$]]]|N|$O|$5|P|Q|R|C|$S|T]]]]

I prefer <a href="https://guava.dev/releases/16.0/api/docs/com/google/common/base/Joiner.html" rel="nofollow noreferrer">Guava</a> over Apache StringUtils for this particular problem:
<pre><code>Joiner.on(separator).join(array)
</code></pre>
Compared to StringUtils, the Joiner API has a fluent design and is a bit more flexible, e.g. <code>null</code> elements may be skipped or replaced by a placeholder. Also, <code>Joiner</code> has a feature for joining maps with a separator between key and value.

blocks|key|1372018|text|Apache+Commons+Lang确实有一个StringUtils.join方法，它可以用指定的分隔符将String数组连接在一起。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1372019|例如：|1372020|String[]+s+=+new+String[]+{"a",+"b",+"c"};
String+joined+=+StringUtils.join(s,+",");++//+"a,b,c"|code-block|syntax|javascript|1372021|但是，我怀疑，正如您所提到的，在上述方法的实际实现中，一定存在某种条件或子字符串处理。|1372022|如果我要执行String连接，并且没有任何其他理由使用Commons+Lang，我可能会使用自己的原因来减少对外部库的依赖。|1372023|entityMap|0|LINK|mutability|MUTABLE|url|http://commons.apache.org/proper/commons-lang/|1|http://commons.apache.org/proper/commons-lang/javadocs/api-2.6/org/apache/commons/lang/StringUtils.html#join(java.util.Collection,%2520char)^0|O|G|1I|6|0|J|0|O|G|1|0|0|0|0|6|6|0^^$0|@$1|2|3|4|5|6|7|10|8|@$9|11|A|12|B|C]|$9|13|A|14|B|C]]|D|@$9|15|A|16|1|17]|$9|18|A|19|1|1A]]|E|$]]|$1|F|3|G|5|6|7|1B|8|@]|D|@]|E|$]]|$1|H|3|I|5|J|7|1C|8|@]|D|@]|E|$K|L]]|$1|M|3|N|5|6|7|1D|8|@]|D|@]|E|$]]|$1|O|3|P|5|6|7|1E|8|@$9|1F|A|1G|B|C]]|D|@]|E|$]]|$1|Q|3|-4|5|6|7|1H|8|@]|D|@]|E|$]]]|R|$S|$5|T|U|V|E|$W|X]]|Y|$5|T|U|V|E|$W|Z]]]]

<a href="http://commons.apache.org/proper/commons-lang/" rel="noreferrer">Apache Commons Lang</a> does indeed have a <a href="http://commons.apache.org/proper/commons-lang/javadocs/api-2.6/org/apache/commons/lang/StringUtils.html#join(java.util.Collection,%20char)" rel="noreferrer"><code>StringUtils.join</code></a> method which will connect <code>String</code> arrays together with a specified separator.

For example:

<pre><code>String[] s = new String[] {"a", "b", "c"};
String joined = StringUtils.join(s, ","); // "a,b,c"
</code></pre>

However, I suspect that, as you mention, there must be some kind of conditional or substring processing in the actual implementation of the above mentioned method.

If I were to perform the <code>String</code> joining and didn't have any other reasons to use Commons Lang, I would probably roll my own to reduce the number of dependencies to external libraries.

blocks|key|1372255|text|一个快速和简单的解决方案，没有任何第三方包括。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1372256|public+static+String+strJoin(String[]+aArr,+String+sSep)+{
++++StringBuilder+sbStr+=+new+StringBuilder();
++++for+(int+i+=+0,+il+=+aArr.length;+i+<+il;+i%2B%2B)+{
++++++++if+(i+>+0)
++++++++++++sbStr.append(sSep);
++++++++sbStr.append(aArr[i]);
++++}
++++return+sbStr.toString();
}|code-block|syntax|javascript|1372257|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

A fast and simple solution without any 3rd party includes.

<pre><code>public static String strJoin(String[] aArr, String sSep) {
 StringBuilder sbStr = new StringBuilder();
 for (int i = 0, il = aArr.length; i &lt; il; i++) {
 if (i &gt; 0)
 sbStr.append(sSep);
 sbStr.append(aArr[i]);
 }
 return sbStr.toString();
}
</code></pre>

blocks|key|1156946|text|“我确信有一种经过认证的有效方法(Apache+Commons?)”|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1156947|是的，显然是|1156948|StringUtils.join(array,+separator)|code-block|syntax|javascript|1156949|http://www.java2s.com/Code/JavaAPI/org.apache.commons.lang/StringUtilsjoinObjectarrayStringseparator.htm|offset|length|1156950|entityMap|0|LINK|mutability|MUTABLE|url^0|0|0|0|0|2W|0|0^^$0|@$1|2|3|4|5|6|7|T|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|U|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|V|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|W|8|@]|9|@$K|X|L|Y|1|Z]]|A|$]]|$1|M|3|-4|5|6|7|10|8|@]|9|@]|A|$]]]|N|$O|$5|P|Q|R|A|$S|J]]]]

"I'm sure there is a certified, efficient way to do it (Apache Commons?)"

yes, apparenty it's

<pre><code>StringUtils.join(array, separator)
</code></pre>

<a href="http://www.java2s.com/Code/JavaAPI/org.apache.commons.lang/StringUtilsjoinObjectarrayStringseparator.htm" rel="noreferrer">http://www.java2s.com/Code/JavaAPI/org.apache.commons.lang/StringUtilsjoinObjectarrayStringseparator.htm</a>

blocks|key|1157284|text|在Java1.8中有一个新的StringJoiner+class+-因此不需要Guava或Apache+Commons：|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1157285|String+str+=+new+StringJoiner(",").add("a").add("b").add("c").toString();|code-block|syntax|javascript|1157286|或者直接在新的流api中使用集合：|1157287|String+str+=+Arrays.asList("a",+"b",+"c").stream().collect(Collectors.joining(","));|1157288|entityMap|0|LINK|mutability|MUTABLE|url|https://docs.oracle.com/javase/8/docs/api/java/util/StringJoiner.html^0|E|I|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@$A|V|B|W|1|X]]|C|$]]|$1|D|3|E|5|F|7|Y|8|@]|9|@]|C|$G|H]]|$1|I|3|J|5|6|7|Z|8|@]|9|@]|C|$]]|$1|K|3|L|5|F|7|10|8|@]|9|@]|C|$G|H]]|$1|M|3|-4|5|6|7|11|8|@]|9|@]|C|$]]]|N|$O|$5|P|Q|R|C|$S|T]]]]

With Java 1.8 there is a new <a href="https://docs.oracle.com/javase/8/docs/api/java/util/StringJoiner.html" rel="noreferrer">StringJoiner class</a> - so no need for Guava or Apache Commons:

<pre><code>String str = new StringJoiner(",").add("a").add("b").add("c").toString();
</code></pre>

Or using a collection directly with the new stream api:

<pre><code>String str = Arrays.asList("a", "b", "c").stream().collect(Collectors.joining(","));
</code></pre>

blocks|key|1157094|text|您可以对正则表达式使用replace和replaceAll。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1157095|String[]+strings+=+{"a",+"b",+"c"};

String+result+=+Arrays.asList(strings).toString().replaceAll("(%5E\\[%7C\\]$)",+"").replace(",+",+",");|code-block|syntax|javascript|1157096|因为Arrays.asList().toString()会生成："a，b，c"，所以我们执行replaceAll来删除第一个和最后一个括号，然后(可选)您可以更改"，“(新分隔符)的"，”序列。|offset|length|style|CODE|1157097|精简版(字符数较少)：|1157098|String[]+strings+=+{"a",+"b",+"c"};

String+result+=+(""+%2B+Arrays.asList(strings)).replaceAll("(%5E.%7C.$)",+"").replace(",+",+","+);|1157099|正则表达式是非常强大的，特别是字符串方法"replaceFirst“和"replaceAll”。试一试。|1157100|entityMap^0|0|0|2|Q|1A|A|0|0|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|V|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|W|8|@$I|X|J|Y|K|L]|$I|Z|J|10|K|L]]|9|@]|A|$]]|$1|M|3|N|5|6|7|11|8|@]|9|@]|A|$]]|$1|O|3|P|5|D|7|12|8|@]|9|@]|A|$E|F]]|$1|Q|3|R|5|6|7|13|8|@]|9|@]|A|$]]|$1|S|3|-4|5|6|7|14|8|@]|9|@]|A|$]]]|T|$]]

You can use replace and replaceAll with regular expressions.

<pre><code>String[] strings = {"a", "b", "c"};

String result = Arrays.asList(strings).toString().replaceAll("(^\\[|\\]$)", "").replace(", ", ",");
</code></pre>

Because <code>Arrays.asList().toString()</code> produces: "[a, b, c]", we do a <code>replaceAll</code> to remove the first and last brackets and then (optionally) you can change the ", " sequence for "," (your new separator).

A stripped version (fewer chars):

<pre><code>String[] strings = {"a", "b", "c"};

String result = ("" + Arrays.asList(strings)).replaceAll("(^.|.$)", "").replace(", ", "," );
</code></pre>

Regular expressions are very powerful, specially String methods "replaceFirst" and "replaceAll". Give them a try.

blocks|key|1372208|text|所有这些其他答案都包括运行时开销...比如使用ArrayList.toString().replaceAll(...)是非常浪费的。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1372209|我将给出零开销的最优算法；它看起来不像其他选项那么漂亮，但在内部，这就是它们都在做的事情(在成堆的其他隐藏检查、多个数组分配和其他crud之后)。|1372210|因为您已经知道您正在处理字符串，所以可以通过手动执行所有操作来节省大量的数组分配。这并不美观，但是如果您跟踪其他实现进行的实际方法调用，您会发现它具有尽可能最小的运行时开销。|1372211|public+static+String+join(String+separator,+String+...+values)+{
++if+(values.length==0)return+"";//need+at+least+one+element
++//all+string+operations+use+a+new+array,+so+minimize+all+calls+possible
++char[]+sep+=+separator.toCharArray();

++//+determine+final+size+and+normalize+nulls
++int+totalSize+=+(values.length+-+1)+*+sep.length;//+separator+size
++for+(int+i+=+0;+i+<+values.length;+i%2B%2B)+{
++++if+(values[i]+==+null)
++++++values[i]+=+"";
++++else
++++++totalSize+%2B=+values[i].length();
++}

++//exact+size;+no+bounds+checks+or+resizes
++char[]+joined+=+new+char[totalSize];
++int+pos+=+0;
++//note,+we+are+iterating+all+the+elements+except+the+last+one
++for+(int+i+=+0,+end+=+values.length-1;+i+<+end;+i%2B%2B)+{
++++System.arraycopy(values[i].toCharArray(),+0,+
++++++joined,+pos,+values[i].length());
++++pos+%2B=+values[i].length();
++++System.arraycopy(sep,+0,+joined,+pos,+sep.length);
++++pos+%2B=+sep.length;
++}
++//now,+add+the+last+element;+
++//this+is+why+we+checked+values.length+==+0+off+the+hop
++System.arraycopy(values[values.length-1].toCharArray(),+0,
++++joined,+pos,+values[values.length-1].length());

++return+new+String(joined);
}|code-block|syntax|javascript|1372212|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|N|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|O|8|@]|9|@]|A|$]]|$1|F|3|G|5|H|7|P|8|@]|9|@]|A|$I|J]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

All of these other answers include runtime overhead... like using ArrayList.toString().replaceAll(...) which are very wasteful.

I will give you the optimal algorithm with zero overhead;
it doesn't look as pretty as the other options, but internally, this is what they are all doing (after piles of other hidden checks, multiple array allocation and other crud).

Since you already know you are dealing with strings, you can save a bunch of array allocations by performing everything manually. This isn't pretty, but if you trace the actual method calls made by the other implementations, you'll see it has the least runtime overhead possible.

<pre><code>public static String join(String separator, String ... values) {
 if (values.length==0)return "";//need at least one element
 //all string operations use a new array, so minimize all calls possible
 char[] sep = separator.toCharArray();

 // determine final size and normalize nulls
 int totalSize = (values.length - 1) * sep.length;// separator size
 for (int i = 0; i &lt; values.length; i++) {
 if (values[i] == null)
 values[i] = "";
 else
 totalSize += values[i].length();
 }

 //exact size; no bounds checks or resizes
 char[] joined = new char[totalSize];
 int pos = 0;
 //note, we are iterating all the elements except the last one
 for (int i = 0, end = values.length-1; i &lt; end; i++) {
 System.arraycopy(values[i].toCharArray(), 0, 
 joined, pos, values[i].length());
 pos += values[i].length();
 System.arraycopy(sep, 0, joined, pos, sep.length);
 pos += sep.length;
 }
 //now, add the last element; 
 //this is why we checked values.length == 0 off the hop
 System.arraycopy(values[values.length-1].toCharArray(), 0,
 joined, pos, values[values.length-1].length());

 return new String(joined);
}
</code></pre>

blocks|key|1371889|text|它在StringUtils中：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1371890|http://www.java2s.com/Code/JavaAPI/org.apache.commons.lang/StringUtilsjoinObjectarrayStringseparator.htm|offset|length|1371891|entityMap|0|LINK|mutability|MUTABLE|url^0|0|0|2W|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|N|8|@]|9|@$D|O|E|P|1|Q]]|A|$]]|$1|F|3|-4|5|6|7|R|8|@]|9|@]|A|$]]]|G|$H|$5|I|J|K|A|$L|C]]]]

it's in StringUtils:

<a href="http://www.java2s.com/Code/JavaAPI/org.apache.commons.lang/StringUtilsjoinObjectarrayStringseparator.htm" rel="noreferrer">http://www.java2s.com/Code/JavaAPI/org.apache.commons.lang/StringUtilsjoinObjectarrayStringseparator.htm</a>

blocks|key|1157399|text|此选项快速且清晰：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1157400|++public+static+String+join(String+separator,+String...+values)+{
++++StringBuilder+sb+=+new+StringBuilder(128);
++++int+end+=+0;
++++for+(String+s+:+values)+{
++++++if+(s+!=+null)+{
++++++++sb.append(s);
++++++++end+=+sb.length();
++++++++sb.append(separator);
++++++}
++++}
++++return+sb.substring(0,+end);
++}|code-block|syntax|javascript|1157401|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

This options is fast and clear:

<pre><code> public static String join(String separator, String... values) {
 StringBuilder sb = new StringBuilder(128);
 int end = 0;
 for (String s : values) {
 if (s != null) {
 sb.append(s);
 end = sb.length();
 sb.append(separator);
 }
 }
 return sb.substring(0, end);
 }
</code></pre>

blocks|key|1157354|text|这个小函数总是派上用场。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1157355|public+static+String+join(String[]+strings,+int+startIndex,+String+separator)+{
++++StringBuffer+sb+=+new+StringBuffer();
++++for+(int+i=startIndex;+i+<+strings.length;+i%2B%2B)+{
++++++++if+(i+!=+startIndex)+sb.append(separator);
++++++++sb.append(strings[i]);
++++}
++++return+sb.toString();
}|code-block|syntax|javascript|1157356|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

This small function always comes in handy.

<pre><code>public static String join(String[] strings, int startIndex, String separator) {
 StringBuffer sb = new StringBuffer();
 for (int i=startIndex; i &lt; strings.length; i++) {
 if (i != startIndex) sb.append(separator);
 sb.append(strings[i]);
 }
 return sb.toString();
}
</code></pre>

blocks|key|1157567|text|我所采用的方法是从Java+1.0开始发展起来的，它提供了可读性并维护了与旧Java版本向后兼容的合理选项，同时还提供了替代apache+commons-lang方法签名的方法签名。出于性能原因，我可以看到对使用Arrays.asList的一些可能的反对意见，但我更喜欢具有合理默认值的帮助器方法，而不是重复执行实际工作的一个方法。这种方法为可靠的方法提供了适当的入口点，该方法在调用之前不需要进行数组/列表转换。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1157568|Java版本兼容性的可能变体包括用StringBuffer+(Java1.0)替换StringBuilder+(Java1.5)，去掉Java1.5迭代器，并从集合(Java1.2)中删除通用通配符(Java1.5)。如果要进一步实现向后兼容性，请删除使用Collection的方法，并将逻辑移到基于数组的方法中。|1157569|public+static+String+join(String[]+values)
{
++++return+join(values,+',');
}

public+static+String+join(String[]+values,+char+delimiter)
{
++++return+join(Arrays.asList(values),+String.valueOf(delimiter));
}

//+To+match+Apache+commons-lang:+StringUtils.join(values,+delimiter)
public+static+String+join(String[]+values,+String+delimiter)
{
++++return+join(Arrays.asList(values),+delimiter);
}

public+static+String+join(Collection<?>+values)
{
++++return+join(values,+',');
}

public+static+String+join(Collection<?>+values,+char+delimiter)
{
++++return+join(values,+String.valueOf(delimiter));
}

public+static+String+join(Collection<?>+values,+String+delimiter)
{
++++if+(values+==+null)
++++{
++++++++return+new+String();
++++}

++++StringBuffer+strbuf+=+new+StringBuffer();

++++boolean+first+=+true;

++++for+(Object+value+:+values)
++++{
++++++++if+(!first)+{+strbuf.append(delimiter);+}+else+{+first+=+false;+}
++++++++strbuf.append(value.toString());
++++}

++++return+strbuf.toString();
}|code-block|syntax|javascript|1157570|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|L|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|M|8|@]|9|@]|A|$G|H]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

The approach that I've taken has evolved since Java 1.0 to provide readability and maintain reasonable options for backward-compatibility with older Java versions, while also providing method signatures that are drop-in replacements for those from apache commons-lang. For performance reasons, I can see some possible objections to the use of Arrays.asList but I prefer helper methods that have sensible defaults without duplicating the one method that performs the actual work. This approach provides appropriate entry points to a reliable method that does not require array/list conversions prior to calling.

Possible variations for Java version compatibility include substituting StringBuffer (Java 1.0) for StringBuilder (Java 1.5), switching out the Java 1.5 iterator and removing the generic wildcard (Java 1.5) from the Collection (Java 1.2). If you want to take backward compatibility a step or two further, delete the methods that use Collection and move the logic into the array-based method.

<pre><code>public static String join(String[] values)
{
 return join(values, ',');
}

public static String join(String[] values, char delimiter)
{
 return join(Arrays.asList(values), String.valueOf(delimiter));
}

// To match Apache commons-lang: StringUtils.join(values, delimiter)
public static String join(String[] values, String delimiter)
{
 return join(Arrays.asList(values), delimiter);
}

public static String join(Collection&lt;?&gt; values)
{
 return join(values, ',');
}

public static String join(Collection&lt;?&gt; values, char delimiter)
{
 return join(values, String.valueOf(delimiter));
}

public static String join(Collection&lt;?&gt; values, String delimiter)
{
 if (values == null)
 {
 return new String();
 }

 StringBuffer strbuf = new StringBuffer();

 boolean first = true;

 for (Object value : values)
 {
 if (!first) { strbuf.append(delimiter); } else { first = false; }
 strbuf.append(value.toString());
 }

 return strbuf.toString();
}
</code></pre>

blocks|key|1372507|text|public+String+join(String[]+str,+String+separator){
++++String+retval+=+"";
++++for+(String+s:+str){+retval%2B=+separator+%2B+s;}
++++return+retval.replaceFirst(separator,+"");
}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1372508|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>public String join(String[] str, String separator){
 String retval = "";
 for (String s: str){ retval+= separator + s;}
 return retval.replaceFirst(separator, "");
}
</code></pre>

See <a href="https://stackoverflow.com/questions/455438/opposite-of-string-split-with-separators-net">Related .NET question</a> 

I'm looking for a quick and easy way to do exactly the opposite of split
so that it will cause <code>["a","b","c"]</code> to become <code>"a,b,c"</code>

Iterating through an array requires either adding a condition (if this is not the last element, add the seperator) or using substring to remove the last separator.

I'm sure there is a certified, efficient way to do it (Apache Commons?)

How do you prefer doing it in your projects?

A quick and easy way to join array elements with a separator (the opposite of split) in Java

Java

请参阅我正在寻找一种快速而简单的方法来做与拆分正好相反的事情，这样它就会使["a","b","c"]成为"a,b,c"迭代数组需要添加条件(如果这不是最后一个元素，则添加分隔符)或使用子字符串删除最后一个分隔符。我确信有一种经过认证的有效方法(Apache Commons?)在你的项目中，你更喜欢怎么做？

问Java中使用分隔符(与split相反)连接数组元素的一种快速而简单的方法
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