Add model for FileChannel.lock() returning not null

Reviewed By: jvillard

Differential Revision: D2631231

fb-gh-sync-id: e5a3476

infer/models/java/src/java/nio/channels/FileChannel.java

@@ -9,7 +9,9 @@
 
 package java.nio.channels;
 
+import com.facebook.infer.models.InferBuiltins;
 import java.nio.channels.spi.AbstractInterruptibleChannel;
+import java.nio.channels.FileLock;
 
 public abstract class FileChannel extends AbstractInterruptibleChannel {
 
@@ -23,4 +25,12 @@ public abstract class FileChannel extends AbstractInterruptibleChannel {
 
         private String displayName;
     }
+
+    private native FileLock getFileLock();
+
+    FileLock lock() {
+        FileLock f = getFileLock();
+        InferBuiltins.assume(f != null);
+        return f;
+    }
 }