Convert Array to string in Java/Groovy

Question

I have a list like this:

List tripIds = new ArrayList()

def sql = Sql.newInstance("jdbc:mysql://localhost:3306/steer", "root", "", "com.mysql.jdbc.Driver")
        
sql.eachRow("SELECT trip.id from trip JOIN department WHERE organization_id = trip.client_id AND department.id = 1") {
  println "Gromit likes ${it.id}"
  tripIds << it.id
} 

On printing tripids gives me value:

  [1,2,3,4,5,6,]

I want to convert this list to simple string like:

 1,2,3,4,5,6

How can I do this?

Solution 1

Use join, e.g.,

tripIds.join(", ")

---

Unrelated, but if you just want to create a list of something from another list, you'd be better off doing something like a map or collect instead of manually creating a list and appending to it, which is less idiomatic, e.g. (untested),

def sql = Sql.newInstance("jdbc:mysql://localhost:3306/steer", "root", "", "com.mysql.jdbc.Driver")
def tripIds = sql.map { it.id }

Or if you only care about the resulting string,

def tripIds = sql.map { it.id }.join(", ")

Solution 2

In groovy:

def myList = [1,2,3,4,5]
def asString = myList.join(", ")

Solution 3

Use the join method that Groovy addes to Collection

List l = [1,2,3,4,5,6]
assert l.join(',') == "1,2,3,4,5,6"

Comments

[Dave Newton]

Seems like a lot of work. Why repeat the code for appending tripIds.get(i) in both conditions? For that matter, why show the code for doing the creation twice; wouldn't it be more vertical-space-friendly to put it in a method and just call it from the example?

[Dónal]

I assume you get paid by the line?