Stringutils.join()

 private static final String[] str = {"1","2","3","4"};
 String str2 = StringUtils.join(str, "|");
 
 System.out.println(str2);

commons.lang3.StringUtils

StringUtils.join(Object array[],String separator)   

将数组以符号或其他字符串为间隔组成新的字符串

Object array[] 需要转换的数组。separator组成新串的间隔符号，如 ","  "|"   

 输出结果：1|2|3|4