ykushch

public class CustomCronExpression extends CronExpression {
    private static final String DELIMITER = " ";
 /**
  * Constructs a new <CODE>CronExpression</CODE> based on the specified
  * parameter.
  *
  * @param cronExpression String representation of the cron expression the
  *       new object should represent
  * @throws java.text.ParseException if the string expression cannot be parsed into a valid
  *         <CODE>CronExpression</CODE>

ykushch

Latency numbers every programmer should know

L1 cache reference ......................... 0.5 ns
Branch mispredict ............................ 5 ns
L2 cache reference ........................... 7 ns
Mutex lock/unlock ........................... 25 ns
Main memory reference ...................... 100 ns             
Compress 1K bytes with Zippy ............. 3,000 ns  =   3 µs
Send 2K bytes over 1 Gbps network ....... 20,000 ns  =  20 µs
SSD random read ........................ 150,000 ns  = 150 µs

Read 1 MB sequentially from memory ..... 250,000 ns = 250 µs

ykushch

#System Design Cheatsheet

Picking the right architecture = Picking the right battles + Managing trade-offs

##Basic Steps

1. Clarify and agree on the scope of the system

• User cases (description of sequences of events that, taken together, lead to a system doing something useful)
  • Who is going to use it?
  • How are they going to use it?

ykushch

If:

- you add and commit with the wrong email address in git, and
- your remote has a hook set up to prevent you from pushing with the bad address

Then you need to amend the author of your commit before push can succeed:

1. fix your email address in git config:

$ git config user.name "Your Name"

ykushch

# image that solves PID 1 issue
FROM phusion/baseimage:0.9.17

# make sure that package repository is up to date
RUN \
  sed -i 's/# \(.*multiverse$\)/\1/g' /etc/apt/sources.list && \
  apt-get update && \
  apt-get -y upgrade && \
  locale-gen en_US.UTF-8

ykushch

FROM ykushch/java8

ENV TOMCAT_MAJOR_VERSION 8
ENV TOMCAT_MINOR_VERSION 8.0.20
ENV CATALINA_HOME /opt/tomcat

RUN apt-get update && \
    apt-get install -yq --no-install-recommends pwgen ca-certificates && \
    apt-get clean && \
    rm -rf /var/lib/apt/lists/*

ykushch

# Set variables in .bashrc file

# don't forget to change your path correctly!

export GOPATH=$HOME/golang
export GOROOT=/usr/local/opt/go/libexec
export PATH=$PATH:$GOPATH/bin
export PATH=$PATH:$GOROOT/bin

ykushch

df -PH | grep -vE '^Filesystem|none|cdrom' | awk '{ print $5 " " $1 }' | while read -r output;

do
  echo "$output"
  usep=$(echo "$output" | awk '{ print $1}' | cut -d'%' -f1  )
  partition=$(echo "$output" | awk '{ print $2 }' )

  if [ "$usep" -ge 90 ]; then
    echo "Running out of space \"$partition ($usep%)\" on $(hostname) as on $(date)" |
    mail -s "Alert: Almost out of disk space $usep%" -r system@server [email protected]

ykushch

git branch -m old_branch new_branch         # Rename branch locally    
git push origin :old_branch                 # Delete the old branch    
git push --set-upstream origin new_branch   # Push the new branch, set local branch to track the new remote

ykushch

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class Solution {

    public static int[] counts(int[] nums, int[] maxes) {
        Arrays.sort(nums);
        List<Integer> result = new ArrayList<>();
        for (int m : maxes) {