How do I parse a YAML file in groovy?

I am adding here the same example, but implemented with the native YAMLSlurper (Groovy 3.x+):

import groovy.yaml.YamlSlurper

def exampleYaml=""'\
---
- subject: "maths"
- subject: "chemistry"
'''

List example = new YamlSlurper().parseText(exampleYaml)
// If your source is a File
// List example = new YamlSlurper().parse("example.yaml" as File)

example.each{println it.subject}

For previous versions (Original answer):

snakeyaml is a library to parse YAML files. Easy to use in groovy.

UPDATE: changed type of the example variable to List, as the example file’s top level element is a collection

@Grab('org.yaml:snakeyaml:1.17')

import org.yaml.snakeyaml.Yaml

Yaml parser = new Yaml()
List example = parser.load(("example.yaml" as File).text)

example.each{println it.subject}

Full documentation of snakeyaml:

https://bitbucket.org/snakeyaml/snakeyaml/wiki/Documentation