$ java -Xmx64m LineCount reader big.log
reader        lines=9,623,347 chars=990,376,717 time=1,288 ms  gc=37 collections / 31 ms  (-Xmx64 MB)
$ java -Xmx64m LineCount scanner big.log
scanner       lines=9,623,347 chars=990,376,717 time=6,233 ms  gc=140 collections / 116 ms  (-Xmx64 MB)
$ java -Xmx64m LineCount lines big.log
lines         lines=9,623,347 chars=990,376,717 time=1,179 ms  gc=37 collections / 32 ms  (-Xmx64 MB)
$ java -Xmx64m LineCount readAllLines big.log
readAllLines  OutOfMemoryError: Java heap space   (-Xmx64 MB)

How much heap does readAllLines need for this file?
$ java -Xmx1g LineCount readAllLines big.log
readAllLines  OutOfMemoryError: Java heap space   (-Xmx1024 MB)
$ java -Xmx2g LineCount readAllLines big.log
readAllLines  lines=9,623,347 chars=990,376,717 time=2,872 ms  gc=24 collections / 922 ms  (-Xmx2048 MB)
$ java -Xmx3g LineCount readAllLines big.log
readAllLines  lines=9,623,347 chars=990,376,717 time=2,729 ms  gc=23 collections / 949 ms  (-Xmx3072 MB)
$ java -Xmx4g LineCount readAllLines big.log
readAllLines  lines=9,623,347 chars=990,376,717 time=2,862 ms  gc=23 collections / 905 ms  (-Xmx4096 MB)

And the streaming reader at a tiny heap:
$ java -Xmx16m LineCount reader big.log
reader        lines=9,623,347 chars=990,376,717 time=1,347 ms  gc=171 collections / 101 ms  (-Xmx16 MB)