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Posted By

thebugslayer on 06/03/07


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groovy shortcut


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doctorillo


Sorting map keys by comparing it's values

 / Published in: Java
 

This demonstrate the expressiveness of Groovy vs Java.

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  1. import java.util.*;
  2.  
  3. //
  4. // Groovy version of "Sort keys by values" is:
  5. //    keys.sort{ lang[it] }
  6. // That's one line replacement!!!
  7. //
  8.  
  9. class MapSort {
  10. 	public static void main(String[] args){
  11. 		Map lang = new HashMap();
  12. 		lang.put(0, "Java");
  13. 		lang.put(1, "Groovy");
  14. 		lang.put(2, "Ruby");
  15. 		lang.put(3, "Python");
  16. 		lang.put(4, "C#");
  17. 		lang.put(5, "C++");
  18. 		lang.put(6, "Perl");
  19.  
  20. 		List keys = new ArrayList(lang.keySet());
  21.  
  22. 		//Sort keys by values.
  23. 		final Map langForComp = lang;
  24. 		Collections.sort(keys, 
  25. 			new Comparator(){
  26. 				public int compare(Object left, Object right){
  27. 					Integer leftKey = (Integer)left;
  28. 					Integer rightKey = (Integer)right;
  29.  
  30. 					String leftValue = (String)langForComp.get(leftKey);
  31. 					String rightValue = (String)langForComp.get(rightKey);
  32. 					return leftValue.compareTo(rightValue);
  33. 				}
  34. 			});
  35.  
  36. 		//List the key value
  37. 		for(Iterator i=keys.iterator(); i.hasNext();){
  38. 			Object k = i.next();
  39. 			System.out.println(k + " " + lang.get(k));
  40. 		}
  41. 	}
  42. }

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Posted By: hohonuuli on June 8, 2007

The equivalent Groovy code to the Java shown is actually:

// create Map def lang = [0:"Java", 1:"Groovy", 2:"Ruby", 3:"Python", 4:"C#", 5:"C++", 6:"Perl"] // Sort the keys by value def keys = lang.keySet().sort {lang[it]} // List the key value keys.each { println "${it} ${lang[it]}" }

Also, the Java code for Java 5 and 6 could be more like:

final Map lang = new HashMap() {{ put(0, "Java"); put(1, "Groovy"); put(2, "Ruby"); put(3, "Python"); put(4, "C#"); put(5, "C++"); put(6, "Perl"); }}; List keys = new ArrayList(lang.keySet()); Collections.sort(keys, new Comparator() { public int compare(Integer left, Integer right) { return lang.get(left).compareTo(lang.get(right)) } }); for (Integer k : keys) { System.out.println(k + " " lang.get(k); }

Groovy definitly requires WAY less scaffolding than Java. On the other hand Java is WAY WAY faster than groovy. (Nothing in life comes free ;-)

Posted By: hohonuuli on June 8, 2007

The equivalent Groovy code to the Java shown is actually:


// create Map 
def lang = [0:"Java", 1:"Groovy", 2:"Ruby", 3:"Python", 4:"C#", 5:"C++", 6:"Perl"] 
// Sort the keys by value 
def keys = lang.keySet().sort {lang[it]} 
// List the key value 
keys.each { println "${it} ${lang[it]}" }

Also, the Java code for Java 5 and 6 could be more like:


final Map lang = new HashMap() {{ 
    put(0, "Java"); put(1, "Groovy"); put(2, "Ruby"); 
    put(3, "Python"); put(4, "C#"); put(5, "C++"); 
    put(6, "Perl"); }}; 
List keys = new ArrayList(lang.keySet()); 
Collections.sort(keys, new Comparator() { 
    public int compare(Integer left, Integer right) { 
        return lang.get(left).compareTo(lang.get(right)) 
    } 
}); 
for (Integer k : keys) { System.out.println(k + " " lang.get(k); }

Groovy definitly requires WAY less scaffolding than Java. On the other hand Java is WAY WAY faster than groovy. (Nothing in life comes free ;-)

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