title: java.util.regex.PatternSyntaxException on Android
body: <p>I am getting a <code>java.util.regex.PatternSyntaxException</code> when trying to call string.split()
  with the regex <code>(?&lt;=}),(?=\\{)</code> against a string such as "{test},{test}"</p>
  
  <p>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:</p>
  
  <pre><code>  java.util.regex.PatternSyntaxException: Syntax error U_REGEX_RULE_SYNTAX near index 5:
          (?&lt;=}),(?=\{)
          ^
          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:
          (?&lt;=}),(?=\{)
          ^
          at java.util.regex.Pattern.compileImpl(Native Method)
          at java.util.regex.Pattern.compile(Pattern.java:400)
          at java.util.regex.Pattern.&lt;init&gt;(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)
  </code></pre>
  
  <p>I'm wondering if the Android runtime doesn't support regex lookaheads, can anyone confirm this or offer any suggestions for solving this?</p>