I want to quickly share how you can sort a Map by its key\/value\/field of valueObject; in either ascending or descending order using Groovy<\/p>\n
I created a Now, Sorting maps in ascending order is a simple one line code:<\/p>\n But how about sorting in reverse order. It would have been great to have map.reverse() or map.reverseSort{} available in Groovy. Since none exists, I had to create the following method:<\/p>\n Use either of the Comparator implementations above & use the method:<\/p>\n Hope it helps.<\/p>\n \u2013Map<String, Person><\/code> as follows:<\/p>\n\r\nclass Person {\r\n String name\r\n Date dateOfBirth\r\n\r\n static constraints = {\r\n }\r\n}\r\n\r\nMap \r\n\/\/ Sort by Key(Person's Name):\r\nmap = map.sort {it.key}\r\n\r\n\/\/ Sort by Value(Person Object):\r\nmap = map.sort {it.value}\r\n\r\n\/\/ Sort by a particular field of Value(Date Of Birth):\r\nmap = map.sort {it.value.dateOfBirth}<\/pre>\n\r\nMap reverseSortMap(Map unsortedMap) {\r\n\r\n \/\/ Different implementations of Comparator\r\n \/\/ 1. Reverse Sort by Key(Person's Name):\r\n Comparator comparator = [compare: {a , b ->\r\n b.compareTo(a)\r\n }] as Comparator\r\n\r\n \/\/ 2. Reverse Sort by Value(Person Object):\r\n Comparator comparator = [compare: {a , b ->\r\n unsortedMap.get(b).compareTo(unsortedMap.get(a))\r\n }] as Comparator\r\n\r\n \/\/ 3. Reverse Sort by a particular field of Value(Date Of Birth):\r\n Comparator comparator = [compare: {a , b ->\r\n unsortedMap.get(b).dateOfBirth.compareTo(unsortedMap.get(a).dateOfBirth)\r\n }] as Comparator\r\n\r\n Map sortedMap = new TreeMap(comparator)\r\n sortedMap.putAll(unsortedMap)\r\n\r\n return sortedMap\r\n}<\/pre>\n\r\npeople = reverseSortMap(people)<\/pre>\n
\n~Aman Aggarwal
\naman@intelligrape.com<\/p>\n