Bash字符串处理-13.字符串数组连接

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
Java代码
/***
* 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;
&n

补充：软件开发 , Java ,