jonjack

Notes on installing multiple versions Java on Mac OSX using Homebrew and Jenv.

Install Homebrew

Homebrew is a superb tool for Mac for managing the installation of software. It's core command is brew and it calls packages of software formula. If you are intrigued then you can check out the list of Formula in the brew Github repository.

/usr/bin/ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"

jonjack

The following scenario has multiple Optionals, a real example could be where you are calling multiple validation checks where each check returns an Optional<T>. You then want to check if each Optional contains a value or is empty - returning the first one that has a value. If none contain a value (ie. are instances of Optional.empty) then you return a default value.

In this example we are using Optional<Single> where Single is an RxJava Observer that returns a single value.

import com.google.common.collect.ImmutableList;

jonjack

Assumes you have brew installed.

Install pyenv.

brew install pyenv

Check what versions of python are available.

jonjack

Mac Setup

Fonts

Check out Adobe Fonts.

brew tap caskroom/fonts && brew cask install font-source-code-pro

jonjack

While installing some formula I get:-

The formula built, but is not symlinked into /usr/local

Running brew as root is not allowed.

sudo brew install awscli

jonjack

Check whats available

brew search maven

==> Formulae
maven                maven-completion     maven-shell          maven@3.0            maven@3.1            maven@3.2            maven@3.3

jonjack

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jonjack

import java.time.LocalTime;
import java.util.concurrent.TimeUnit;

public class Timer {
    public static void main(String[] args) {
        LocalTime start = LocalTime.now();
	// some event to be timed
	LocalTime end = LocalTime.now();
	long delta = TimeUnit.NANOSECONDS.toMillis(end.toNanoOfDay() - start.toNanoOfDay());
	System.out.println("Time took: " + Double.valueOf(delta)/1000 + " seconds");

jonjack

import org.joda.time.LocalTime;

public class Timer {
    public static void main(String[] args) {
        LocalTime start = LocalTime.now();
        // some event to be timed
        LocalTime end = LocalTime.now();
        int delta = end.getMillisOfDay() - start.getMillisOfDay();
        System.out.println("Time took: " + Double.valueOf(delta)/1000 + " seconds");
    }

jonjack

We have a method to test which iterates over some List. The example is a validator service which iterates over a List of validators applying each one and returning when one fails ie. it returns an Optional containing an error message (this is just a concrete example to demonstrate Mockito and is not important to understand).

public class SomeValidationService implements ValidationService {

    /* List of validators which all encapsulate some different business validation logic */
    /* This gets injected say via Spring */
    private List<Validator> validators;
 
    public Optional<ErrorMessage> validateAction(final ObjectToValidate obj) {