String str = "  this is string   ";
str = str.replaceAll("\\s+", " ").trim();

要消除字符串开头和结尾的空格，请使用String#trim()方法。然后使用你的mytext。replaceAll("()+"， " ")。

可以使用字符串标记器

 String str = "  hello    there  ";
            StringTokenizer stknzr = new StringTokenizer(str, " ");
            StringBuffer sb = new StringBuffer();
            while(stknzr.hasMoreElements())
            {
                sb.append(stknzr.nextElement()).append(" ");
            }
            System.out.println(sb.toString().trim());

这对我很有效

scan= filter(scan, " [\\s]+", " ");
scan= sac.trim();

其中filter跟在function后面，scan是输入字符串:

public String filter(String scan, String regex, String replace) {
    StringBuffer sb = new StringBuffer();

    Pattern pt = Pattern.compile(regex);
    Matcher m = pt.matcher(scan);

    while (m.find()) {
        m.appendReplacement(sb, replace);
    }

    m.appendTail(sb);

    return sb.toString();
}

管柱。替换(“s+”，“”);

String str = "  this is string   ";
str = str.replaceAll("\\s+", " ").trim();