Unclosed character class near index 1 :[ 轉義符問題

Exception in thread "main" java.util.regex.PatternSyntaxException: Unclosed character class near index 1
:[

at java.util.regex.Pattern.error(Unknown Source)
    at java.util.regex.Pattern.clazz(Unknown Source)
    at java.util.regex.Pattern.sequence(Unknown Source)
    at java.util.regex.Pattern.expr(Unknown Source)
    at java.util.regex.Pattern.compile(Unknown Source)
    at java.util.regex.Pattern.<init>(Unknown Source)
    at java.util.regex.Pattern.compile(Unknown Source)
    at java.lang.String.split(Unknown Source)
    at java.lang.String.split(Unknown Source)
    at test.TestDemo.main(TestDemo.java:11)

出現此錯誤應該是字符轉義出現問題：

System.out.println(str.split(":[")[1]);

解決方案：在[之前加上\\

System.out.println(str.split(":\\[")[1]);