title: maven-compiler-plugin:3.1:compile failed. NullPointerException
body: <p>I got NullPointerException with the maven-compiler-plugin:3.1. I have surveyed similar questions on SOF but in vain attempt. </p>
  
  <p><strong>The command that I ran</strong>: <code>mvn compile</code></p>
  
  <p><strong>The maven environment</strong>:</p>
  
  <pre><code>Apache Maven 3.0.3 (rNON-CANONICAL_2011-12-28_13-22_mein; 2011-12-28 13:22:36-0600)
  Maven home: /soft/maven/3.0.3
  Java version: 1.6.0_38, vendor: Sun Microsystems Inc.
  Java home: /soft/jdk1.6.0_38-arch/jre
  Default locale: en_US, platform encoding: UTF-8
  OS name: "linux", version: "3.13.0-83-generic", arch: "amd64", family: "unix"
  </code></pre>
  
  <p>(It's using 1.6 since this is required by the project, a legacy project)</p>
  
  <p><strong>Error message</strong>:</p>
  
  <pre><code>[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.1:compile (default-compile) on project wikibrain-utils: Execution default-compile of goal org.apache.maven.plugins:maven-compiler-plugin:3.1:compile failed. NullPointerException -&gt; [Help 1]
  org.apache.maven.lifecycle.LifecycleExecutionException: Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.1:compile (default-compile) on project wikibrain-utils: Execution default-compile of goal org.apache.maven.plugins:maven-compiler-plugin:3.1:compile failed.
      at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:225)
      at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:153)
      at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:145)
      at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:84)
      at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:59)
      at org.apache.maven.lifecycle.internal.LifecycleStarter.singleThreadedBuild(LifecycleStarter.java:183)
      at org.apache.maven.lifecycle.internal.LifecycleStarter.execute(LifecycleStarter.java:161)
      at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:319)
      at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:156)
      at org.apache.maven.cli.MavenCli.execute(MavenCli.java:537)
      at org.apache.maven.cli.MavenCli.doMain(MavenCli.java:196)
      at org.apache.maven.cli.MavenCli.main(MavenCli.java:141)
      at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
      at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
      at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
      at java.lang.reflect.Method.invoke(Method.java:597)
      at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced(Launcher.java:290)
      at org.codehaus.plexus.classworlds.launcher.Launcher.launch(Launcher.java:230)
      at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode(Launcher.java:409)
      at org.codehaus.plexus.classworlds.launcher.Launcher.main(Launcher.java:352)
  Caused by: org.apache.maven.plugin.PluginExecutionException: Execution default-compile of goal org.apache.maven.plugins:maven-compiler-plugin:3.1:compile failed.
      at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:110)
      at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:209)
      ... 19 more
  Caused by: java.lang.NullPointerException
      at org.apache.maven.plugin.compiler.AbstractCompilerMojo.hasNewFile(AbstractCompilerMojo.java:1198)
      at org.apache.maven.plugin.compiler.AbstractCompilerMojo.isDependencyChanged(AbstractCompilerMojo.java:1166)
      at org.apache.maven.plugin.compiler.AbstractCompilerMojo.execute(AbstractCompilerMojo.java:648)
      at org.apache.maven.plugin.compiler.CompilerMojo.execute(CompilerMojo.java:129)
      at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:101)
      ... 20 more
  [ERROR]
  [ERROR]
  [ERROR] For more information about the errors and possible solutions, please read the following articles:
  [ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/PluginExecutionException
  [ERROR]
  [ERROR] After correcting the problems, you can resume the build with the command
  [ERROR]   mvn &lt;goals&gt; -rf :wikibrain-utils
  </code></pre>