Skip to main content

Groovy Maps

Using Maps in Groovy is much simpler than in Java. Some key differences are:

  • Map declaration and instantiation are simpler

  • Elements of a Map can be accessed either using the bean style or array style

  • Iterating across Maps is far less verbose in Groovy than in Java



The code sample below is self explanatory



//Declaring and instantiating a Map
def emptyMap = [:]


//Populating a Map
//Notice that the keys which are strings are not
//enclosed within quotes
def population = [Estonia:1299371,
Finland:5250275,
Honduras:7792854,
HongKong:7055071]

//Non string keys must be enclosed in ()
def numbers = [(Integer.valueOf("1")):"One",
(Integer.valueOf("2")):"Two"]


//Accessing Map elements
//Maps can be accessed using bean style and
//array style notations respectively
println "Estonia population: " + population.Estonia
println "Finland population: " + population['Finland']
//Use default values in case key does not exist (if key does not exist, then
//it will be added with the default value)
println "Spain population: " + population.get("Spain", 40525002)

//Iterating over all the entries in a Map
println "Population stats"
population.each { key, value ->
println key + " : " + value
}

println "Numbers as words"
numbers.each() {
println it.key + ":" + it.value
}

//Search within a Map
println 'Countries with a population greater than 1 million'
result = population.findAll {key, value ->
value > 5000000
}
println 'population > 5000000 ' + result.keySet()



Output from running the above program:


Estonia population: 1299371
Finland population: 5250275
Spain population: 40525002
Population stats
Estonia : 1299371
Finland : 5250275
Honduras : 7792854
HongKong : 7055071
Spain : 40525002
Numbers as words
1:One
2:Two
Countries with a population greater than 1 million
population > 5000000 ["HongKong", "Finland", "Spain", "Honduras"]

Comments

Popular posts from this blog

Running your own one person company

Recently there was a post on PuneTech on mom's re-entering the IT work force after a break. Two of the biggest concerns mentioned were : Coping with vast advances (changes) in the IT landscape Balancing work and family responsibilities Since I have been running a one person company for a good amount of time, I suggested that as an option. In this post I will discuss various aspects of running a one person company. Advantages: You have full control of your time. You can choose to spend as much or as little time as you would like. There is also a good chance that you will be able to decide when you want to spend that time. You get to work on something that you enjoy doing. Tremendous work satisfaction. You have the option of working from home. Disadvantages: It can take a little while for the work to get set, so you may not be able to see revenues for some time. It takes a huge amount of discipline to work without a boss, and without deadlines. You will not get the benefits (insuran

Some thoughts on redesigning education

Some time back I read a blog post on redesigning education. It asked some very good questions. Stuff which I had been thinking of myself. I left my thoughts on the blog, but I would also like to start a conversation around these ideas with those who read this blog as well. I would like to know what other people think of the issue of redesigning (college) education. I have often thought about how college education can be improved. To answer this question, we first have to ask a very basic question. What is the purpose of education? To me, we need education for 3 things: To learn more about the world around us To lead positive constructive lives To earn a good living / fulfill our ambitions I think education has to a large extent evolved to fulfill #3 (with a bias towards earning a comfortable living). The semester system, along with multiple choice tests, and grading, has made our education system into an assembly line. Students are pushed into the assembly line, given classes, admini

Testing Groovy domain classes

If you are trying to test Grails domain class constraints by putting your unit test cases in the 'test/unit' directory, then your tests will fail because the domain objects will not have the 'valdate' method. This can be resolved in two ways: Place the test cases inside test/integration (which will slow things down) Use the method 'mockForConstraintsTests(Trail)' to create mock method in your domain class and continue writing your test cases in 'test/unit' What follows is some example code around this finding. I am working on a Groovy on Grails project for a website to help programmers keep up and refresh their skills. I started with some domain classes and then moved on to write some unit tests. When we create a Grails project using grails create-app , it creates several directories, one of which is a directory called 'test' for holding unit tests. This directory contains two directories, 'unit', and 'integration' for uni