title: PatternSyntaxException: Illegal Repetition when using regex in Java
body: <p>I don't know much regex, but I need to match a simple pattern. The following should return true,</p>
  
  <pre><code>Pattern.matches("{\"user_id\" : [0-9]*}", inputLine)
  </code></pre>
  
  <p>when inputLine is</p>
  
  <pre><code>{"user_id" : 34}
  </code></pre>
  
  <p>However, I'm getting this exception:</p>
  
  <pre><code>java.util.regex.PatternSyntaxException: Illegal repetition
  {"user_id" : 24}
      at java.util.regex.Pattern.error(Unknown Source)
      at java.util.regex.Pattern.closure(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.&lt;init&gt;(Unknown Source)
      at java.util.regex.Pattern.compile(Unknown Source)
      at java.util.regex.Pattern.matches(Unknown Source)
      at org.whispercomm.manes.server.http.IntegrationTest.createUser(IntegrationTest.java:173)
      at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
      at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
      at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
      at java.lang.reflect.Method.invoke(Unknown Source)
      at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:45)
      at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15)
      at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:42)
      at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:20)
      at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:28)
      at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:30)
      at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:263)
      at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:68)
      at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:47)
      at org.junit.runners.ParentRunner$3.run(ParentRunner.java:231)
      at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:60)
      at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:229)
      at org.junit.runners.ParentRunner.access$000(ParentRunner.java:50)
      at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:222)
      at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:28)
      at org.junit.runners.ParentRunner.run(ParentRunner.java:300)
      at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:50)
      at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
      at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467)
      at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683)
      at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390)
      at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197)
  </code></pre>
  
  <p>What am I doing wrong?</p>