java.util.regex.PatternSyntaxException on Android

Question

I am getting a java.util.regex.PatternSyntaxException when trying to call string.split() with the regex (?<=}),(?=\\{) against a string such as "{test},{test}"

This works fine when I run it in a unit test on the JVM (ie. not on Android) but on Android I get the following stack trace:

  java.util.regex.PatternSyntaxException: Syntax error U_REGEX_RULE_SYNTAX near index 5:
        (?<=}),(?=\{)
        ^
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1647)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663)
        at android.app.ActivityThread.access$1500(ActivityThread.java:117)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:130)
        at android.app.ActivityThread.main(ActivityThread.java:3683)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:507)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
        at dalvik.system.NativeStart.main(Native Method)
        Caused by: java.util.regex.PatternSyntaxException: Syntax error U_REGEX_RULE_SYNTAX near index 5:
        (?<=}),(?=\{)
        ^
        at java.util.regex.Pattern.compileImpl(Native Method)
        at java.util.regex.Pattern.compile(Pattern.java:400)
        at java.util.regex.Pattern.<init>(Pattern.java:383)
        at java.util.regex.Pattern.compile(Pattern.java:374)
        at java.lang.String.split(String.java:2021)
        at java.lang.String.split(String.java:2002)

I'm wondering if the Android runtime doesn't support regex lookaheads, can anyone confirm this or offer any suggestions for solving this?

the '}' character doesn't need to be escaped and if you try it it makes the regex illegal — Rupert Bates
– Rupert Bates, Commented Jun 17, 2011 at 10:12

agent-j · Accepted Answer · 2011-06-24 15:41:44Z

1

This android/java regex page indicates that lookbehinds are supported and that you have the correct syntax for it.

I don't see how escaping the { can cause a problem with the regex. Have you tried this form of the expression? string ex = "(?<=\\}),(?=\\{)";

answered Jun 24, 2011 at 15:41

agent-j

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1 Comment

Rupert Bates Over a year ago

Do you know I was SO sure I had tried this, I think it must be my C# background and I was escaping it with a single backslash! Thanks.

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