Despite the synchronization added to BufferedInputStream, a NullPointerException can still be generated from the reading thread as by the following stack traces:

in close setting in to null:
        at java.io.BufferedInputStream.close(BufferedInputStream.java:417)
        at java.lang.UNIXProcess$DeferredCloseInputStream.lower(UNIXProcess.java:173)
        at java.lang.UNIXProcess$DeferredCloseInputStream.read(UNIXProcess.java:223)
        at java.io.BufferedInputStream.read1(BufferedInputStream.java:228)
        at java.io.BufferedInputStream.read(BufferedInputStream.java:285)
        at sun.nio.cs.StreamDecoder$CharsetSD.readBytes(StreamDecoder.java:408)
        at sun.nio.cs.StreamDecoder$CharsetSD.implRead(StreamDecoder.java:450)
        at sun.nio.cs.StreamDecoder.read(StreamDecoder.java:182)
        at java.io.InputStreamReader.read(InputStreamReader.java:167)
        at java.io.BufferedReader.fill(BufferedReader.java:136)
        at java.io.BufferedReader.read(BufferedReader.java:157)
        at com.sun.tools.example.debug.tty.VMConnection.dumpStream(VMConnection.java:283)
        at com.sun.tools.example.debug.tty.VMConnection.access$000(VMConnection.java:48)
        at com.sun.tools.example.debug.tty.VMConnection$1.run(VMConnection.java:307)

java.lang.NullPointerException
        at java.io.BufferedInputStream.read(BufferedInputStream.java:287)
        at sun.nio.cs.StreamDecoder$CharsetSD.readBytes(StreamDecoder.java:408)
        at sun.nio.cs.StreamDecoder$CharsetSD.implRead(StreamDecoder.java:450)
        at sun.nio.cs.StreamDecoder.read(StreamDecoder.java:182)
        at java.io.InputStreamReader.read(InputStreamReader.java:167)
        at java.io.BufferedReader.fill(BufferedReader.java:136)
        at java.io.BufferedReader.read(BufferedReader.java:157)
        at com.sun.tools.example.debug.tty.VMConnection.dumpStream(VMConnection.java:283)
        at com.sun.tools.example.debug.tty.VMConnection.access$000(VMConnection.java:48)
        at com.sun.tools.example.debug.tty.VMConnection$1.run(VMConnection.java:307)