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
Java 8中有三种可能性:
List<String> list = Arrays.asList("Alice", "Bob", "Charlie")
String result = String.join(" and ", list);
result = list.stream().collect(Collectors.joining(" and "));
result = list.stream().reduce((t, u) -> t + " and " + u).orElse("");
其他回答
在纯JDK中有一种有趣的方法:
String[] array = new String[] { "Bill", "Bob", "Steve","[Bill]","1,2,3","Apple ][" };
String join = " and ";
String joined = Arrays.toString(array).replaceAll(", ", join)
.replaceAll("(^\\[)|(\\]$)", "");
System.out.println(joined);
输出:
比尔、鲍勃、史蒂夫、[比尔]、1,2,3和苹果][
一个不太完美也不太有趣的方式!
String[] array = new String[] { "7, 7, 7","Bill", "Bob", "Steve", "[Bill]",
"1,2,3", "Apple ][" };
String join = " and ";
for (int i = 0; i < array.length; i++) array[i] = array[i].replaceAll(", ", "~,~");
String joined = Arrays.toString(array).replaceAll(", ", join)
.replaceAll("(^\\[)|(\\]$)", "").replaceAll("~,~", ", ");
System.out.println(joined);
输出:
7,7,7和比尔，鲍勃，史蒂夫和[比尔]，1,2,3和苹果][
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。
另一个解，它是另一个答案的变体
public static String concatStringsWSep(Iterable<String> strings, String separator) {
Iterator<String> it = strings.iterator();
if( !it.hasNext() ) return "";
StringBuilder sb = new StringBuilder(it.next());
while( it.hasNext()) {
sb.append(separator).append(it.next());
}
return sb.toString();
}
你可能想试试Apache Commons StringUtils join方法:
以http://commons.apache.org/lang/api/org/apache/commons/lang/StringUtils.html加入(java.util.Iterator)
我发现Apache StringUtils捡起jdk的懈怠;-)
实现它的一个正统方法是定义一个新函数:
public static String join(String joinStr, String... strings) {
if (strings == null || strings.length == 0) {
return "";
} else if (strings.length == 1) {
return strings[0];
} else {
StringBuilder sb = new StringBuilder(strings.length * 1 + strings[0].length());
sb.append(strings[0]);
for (int i = 1; i < strings.length; i++) {
sb.append(joinStr).append(strings[i]);
}
return sb.toString();
}
}
示例:
String[] array = new String[] { "7, 7, 7", "Bill", "Bob", "Steve",
"[Bill]", "1,2,3", "Apple ][","~,~" };
String joined;
joined = join(" and ","7, 7, 7", "Bill", "Bob", "Steve", "[Bill]", "1,2,3", "Apple ][","~,~");
joined = join(" and ", array); // same result
System.out.println(joined);
输出:
7,7,7和比尔，鲍勃，史蒂夫和[比尔]，1,2,3和苹果][和~，~
