JavaScript有Array.join()
js>["Bill","Bob","Steve"].join(" and ")
Bill and Bob and Steve
Java有这样的东西吗?我知道我可以用StringBuilder自己拼凑一些东西:
static public String join(List<String> list, String conjunction)
{
StringBuilder sb = new StringBuilder();
boolean first = true;
for (String item : list)
{
if (first)
first = false;
else
sb.append(conjunction);
sb.append(item);
}
return sb.toString();
}
. .但是如果像这样的东西已经是JDK的一部分，那么这样做就没有意义了。
当前回答
如果您正在使用Eclipse Collections(以前的GS Collections)，则可以使用makeString()方法。
List<String> list = Arrays.asList("Bill", "Bob", "Steve");
String string = ListAdapter.adapt(list).makeString(" and ");
Assert.assertEquals("Bill and Bob and Steve", string);
如果您可以将List转换为Eclipse Collections类型，那么您就可以摆脱适配器。
MutableList<String> list = Lists.mutable.with("Bill", "Bob", "Steve");
String string = list.makeString(" and ");
如果您只想要一个逗号分隔的字符串，您可以使用不接受参数的makeString()版本。
Assert.assertEquals(
"Bill, Bob, Steve",
Lists.mutable.with("Bill", "Bob", "Steve").makeString());
注意:我是Eclipse Collections的提交者。
其他回答
String.join
在Java 8中，你不需要任何第三方库就可以做到这一点。
如果你想加入一个字符串集合，你可以使用String.join()方法:
List<String> list = Arrays.asList("foo", "bar", "baz");
String joined = String.join(" and ", list); // "foo and bar and baz"
Collectors.joining
如果你有一个非String类型的Collection，你可以使用Stream API来连接Collector:
List<Person> list = Arrays.asList(
new Person("John", "Smith"),
new Person("Anna", "Martinez"),
new Person("Paul", "Watson ")
);
String joinedFirstNames = list.stream()
.map(Person::getFirstName)
.collect(Collectors.joining(", ")); // "John, Anna, Paul"
StringJoiner类可能也很有用。
你可以从Spring框架的StringUtils中使用它。我知道它已经被提到过，但是实际上您可以只使用这段代码，它就可以立即工作，而不需要Spring。
// from https://github.com/spring-projects/spring-framework/blob/master/spring-core/src/main/java/org/springframework/util/StringUtils.java
/*
* Copyright 2002-2017 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
public class StringUtils {
public static String collectionToDelimitedString(Collection<?> coll, String delim, String prefix, String suffix) {
if(coll == null || coll.isEmpty()) {
return "";
}
StringBuilder sb = new StringBuilder();
Iterator<?> it = coll.iterator();
while (it.hasNext()) {
sb.append(prefix).append(it.next()).append(suffix);
if (it.hasNext()) {
sb.append(delim);
}
}
return sb.toString();
}
}
使用java 8收集器，这可以用以下代码完成:
Arrays.asList("Bill", "Bob", "Steve").stream()
.collect(Collectors.joining(" and "));
此外，java 8中最简单的解决方案:
String.join(" and ", "Bill", "Bob", "Steve");
or
String.join(" and ", Arrays.asList("Bill", "Bob", "Steve"));
用java 1.8的流可以使用，
import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;
List<String> list = Arrays.asList("Bill","Bob","Steve").
String str = list.stream().collect(Collectors.joining(" and "));
Java 8确实带来了
Collectors.joining(CharSequence delimiter, CharSequence prefix, CharSequence suffix)
方法，通过对空值使用前缀+后缀，该方法为nullsafe。
它可以以以下方式使用:
String s = stringList.stream().collect(Collectors.joining(" and ", "prefix_", "_suffix"))
收藏家。join (CharSequence delimiter)方法只是在内部调用joining(delimiter， ""， "")。
