双倍 split 应该做的工作：

String token = data.split(" +")[2].split("[\\[:/]")[0];

我想你要找的正则表达式是：

String regex = "([^\\[:/]+).*";
``` `.*` 表示匹配任何字符的0个或多个。在点星前面放一对圆括号 `().*` 创建可以从匹配器中选择的组。因为它是第一组括号，所以它被组1引用。括号内有一个表达式，它匹配一个或多个被求反的字符类 `[^]+` 包含op中指定的字符，特别是“[”、“：”和“/”字符。
下面是一个测试结果的应用程序示例：

package com.stackexchange.stackoverflow;

import java.util.ArrayList;
import java.util.List;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class Question19370191 {
public static void main(String[] args) {
String regex = "([^\[:/]+).*";
Pattern pattern = Pattern.compile(regex);

    List<String> lines = new ArrayList<>();
    lines.add("2013-10-14T22:05:29+00:00 hostname sshd[6359]: Connection closed by 192.168.1.10");
    lines.add("2013-10-14T22:05:29+00:00 hostname sshd:3322 Connection closed by 192.168.1.10");
    lines.add("2013-10-14T22:05:29+00:00 hostname sshd/6359 Connection closed by 192.168.1.10");
    lines.add("2013-10-14T22:05:29+00:00 hostname sshd Connection closed by 192.168.1.10");
    lines.add("2013-10-14T22:05:29+00:00 hostname SSHD[1133] Connection closed by 192.168.1.10");
    lines.add("2013-10-14T22:05:29+00:00 hostname SSH.D[6359]: Connection closed by 192.168.1.10");

    for(String line : lines) {
        String field = line.split("\\s")[2];
        String extraction = "";
        Matcher matcher = pattern.matcher(field);
        if(matcher.matches()) {
            extraction = matcher.group(1);
        }

        System.out.println(String.format("Field \"%-12s\" Extraction \"%s\"", field, extraction));
    }
}

}

它输出以下内容：

Field "sshd[6359]: " Extraction "sshd"
Field "sshd:3322 " Extraction "sshd"
Field "sshd/6359 " Extraction "sshd"
Field "sshd " Extraction "sshd"
Field "SSHD[1133] " Extraction "SSHD"
Field "SSH.D[6359]:" Extraction "SSH.D"

如果您的示例数据与您提供的完全相同：

(?:.+?\s){2}([\w\.]+).+$

解释： (?:.+?\s){2} …匹配到第二个空格 ([^\s[:/]+) …匹配任何不是“”、“：”或“/”的项 .+$ …匹配eol
你想要的东西将在捕获组中 \1

尝试以下操作：

String str = line.split(" ")[2].replaceAll("(.+)(\\[|\\:|\\/).+", "$1");

还没测试过。