# 1) Increase the jvm max heap size. Strict compilation in 2) requires more than 2 GB.
# 2) Strict compilation using error-prone
# 3) Reset the maven options. Parallel testing in 4) launches 2 processes, each requires 1 GB of memory. Increasing the maximum memory may cause OutOfMemory error because the instance of Travis has 4 GB of memory space.
# 4) Parallel unit testing
# Using && instead of independent script steps to make Travis build fail faster, if each step is not successful