How to iterate over list and remove the matched items to create a new list

Question

I am new to groovy Lists, and I have list as shown below:

Class File{
 String name 
 int type
 int revision
}

def fileList = [File1, File2, File3,....]

I want the fileList to have the latest files

1. It should not have the items of same type
2. It should have the highest revision files means, if two or more files have the same type then the list must have the single file with the highest revision.

How do I do this in Groovy?

Answer 1

You can use Collection#groupBy to create a map with an entry for each unique file name. You can then use Map#collect to iterate over the contents of this map and create the list you want. The map's values will be a list of instances of File, so Collection#max will let you search for the one with the highest revision number.

class File {
    String name
    int type
    int revision

    String toString() { "File(name: $name; type: $type; revision: $revision)" }
}

final files = [
    new File(name: 'foo', type: 0, revision: 0),
    new File(name: 'bar', type: 0, revision: 0),
    new File(name: 'bar', type: 0, revision: 1),
    new File(name: 'baz', type: 0, revision: 0),
    new File(name: 'baz', type: 0, revision: 1),
    new File(name: 'baz', type: 1, revision: 1),
]

final result = files.groupBy { it.name }
             . collect { name, revisions -> revisions.max { it.revision } }

I'm not sure what you meant when you said that the list should not have items of the same type. You'll notice that if there are two instances of File with the same name and revision number but different types, this solution picks one arbitrarily.