Bash字符串处理（与Java对照） - 13.字符串数组连接（以指定分隔符合并）

In Java

以指定的分隔符将字符串数组连接成一个字符串的源码

以下代码来自：http://www.oschina.net/code/explore/jsoup-1.4.1/helper/StringUtil.java

    /***
     * Join a collection of strings by a seperator
     * @param strings collection of string objects
     * @param sep string to place between strings
     * @return joined string
     */
    public static String join(Collection<String> strings, String sep) {
        return join(strings.iterator(), sep);
    }

    /***
     * Join a collection of strings by a seperator
     * @param strings iterator of string objects
     * @param sep string to place between strings
     * @return joined string
     */
    public static String join(Iterator<String> strings, String sep) {
        if (!strings.hasNext())
            return "";

        String start = strings.next();
        if (!strings.hasNext()) // only one, avoid builder
            return start;

        StringBuilder sb = new StringBuilder(64).append(start);
        while (strings.hasNext()) {
            sb.append(sep);
            sb.append(strings.next());
        }
        return sb.toString();
    }

StringUtils.join

提供了九种join方法

org.apache.commons.lang.StringUtils join方法写道 static String join(Collection collection, char separator)
Joins the elements of the provided Collection into a single String containing the provided elements.
static String join(Collection collection, String separator)
Joins the elements of the provided Collection into a single String containing the provided elements.
static String join(Iterator iterator, char separator)
Joins the elements of the provided Iterator into a single String containing the provided elements.
static String join(Iterator iterator, String separator)
Joins the elements of the provided Iterator into a single String containing the provided elements.
static String join(Object[] array)
Joins the elements of the provided array into a single String containing the provided list of elements.
static String join(Object[] array, char separator)
Joins the elements of the provided array into a single String containing the provided list of elements.
static String join(Object[] array, char separator, int startIndex, int endIndex)
Joins the elements of the provided array into a single String containing the provided list of elements.
static String join(Object[] array, String separator)
Joins the elements of the provided array into a single String containing the provided list of elements.
static String join(Object[] array, String separator, int startIndex, int endIndex)
Joins the elements of the provided array into a single String containing the provided list of elements. ?

In Bash

将数组中的字符串合并。

数组的定义方式如下：

ARR=(S1 S2 S3)

以空格分隔

格式1：STR=${ARR[*])

格式2：STR=${ARR[@])

格式3：STR="${ARR[*]}"

格式4：STR="${ARR[@]}"

[root@jfht ~]# ARR=(S1 S2 S3)

[root@jfht ~]# echo "${ARR[*]}"
S1 S2 S3

[root@jfht ~]# echo "${ARR[@]}" ???????
S1 S2 S3
[root@jfht ~]#

不分隔

str_join() {

??? local dst

??? for s in "$@"

??? do

??????? dst=${dst}${s}

??? done

??? echo "$dst"

}

正确：str_join "$ARR[@]"

错误：str_join $ARR[@]

错误：str_join "$ARR[*]"

错误：str_join $ARR[*]

[root@jfht ~]# declare -f str_join
str_join ()
{
??? local dst;
??? for s in "$@";
??? do
??????? dst=${dst}${s};
??? done;
??? echo "$dst"
}

[root@jfht ~]# ARR=(yes no 'hello world')
[root@jfht ~]# str_join ${ARR[*]}
yesnohelloworld
[root@jfht ~]# str_join ${ARR[@]}
yesnohelloworld
[root@jfht ~]# str_join "${ARR[*]}"
yes no hello world
[root@jfht ~]# str_join "${ARR[@]}"
yesnohello world
[root@jfht ~]#

以指定分隔符来分隔

实现方式一

str_join_sep ()
{

??? local sep="$1"

??? shift
??? local dst
??? for s in "$@"
??? do

??????? if [ "$dst" ]; then
??????????? dst=${dst}${sep}${s}

??????? else

??????????? dst=${s}

??????? fi
??? done
??? echo "$dst"
}

正确：str_join_sep "$SEP" "$ARR[@]"

注意双引号的使用。

[root@jfht ~]# declare -f str_join_sep
str_join_sep ()
{
??? local sep="$1";
??? shift;
??? local dst;
??? for s in "$@";
??? do
??????? if [ "$dst" ]; then
??????????? dst=${dst}${sep}${s};
??????? else
??????????? dst=${s};
??????? fi;
??? done;
??? echo "$dst"
}
[root@jfht ~]# ARR=(yes no 'hello world')????
[root@jfht ~]# SEP=,
[root@jfht ~]# str_join_sep "$SEP" "${ARR[@]}"
yes,no,hello world
[root@jfht ~]#

实现方式二

str_join_sep ()
{

??? local sep="$1"

??? shift
??? local dst="$1"

??? shift
??? for s in "$@"
??? do

??????? dst=${dst}${sep}${s}

??? done
??? echo "$dst"
}

[root@jfht ~]# declare -f str_join_sep
str_join_sep ()
{
??? local sep="$1";
??? shift;
??? local dst="$1";
??? shift;
??? for s in "$@";
??? do
??????? dst=${dst}${sep}${s};
??? done;
??? echo "$dst"
}
[root@jfht ~]# ARR=(yes no 'hello world')
[root@jfht ~]# SEP=,
[root@jfht ~]# str_join_sep "$SEP" "${ARR[@]}"
yes,no,hello world
[root@jfht ~]# SEP=:
[root@jfht ~]# str_join_sep "$SEP" "${ARR[@]}"
yes:no:hello world
[root@jfht ~]# SEP='|'