Java 8 Lambda:comparator Example __java

In the following example, we'll show you how to use the Java 8 LAMBDA expression to write a comparator that sorts the list collection.

1. Classic Comparator example.

comparator<developer> byname = new comparator<developer> () {
	@Override public
	int Compare ( Developer O1, Developer O2) {return
		o1.getname (). CompareTo (O2.getname ());

2. LAMBDA expression equivalent.

Comparator<developer> byname =
	(Developer O1, Developer O2)->o1.getname (). CompareTo (O2.getname ());

1. Do not use the LAMBDA to achieve sorting The   example demonstrates the ability to sort the age property with a Developer   object. Normally, you would use Collections.sort to implement the anonymous comparator  comparer, as follows: Testsorting.java

Package com.mkyong.java8;
Import Java.math.BigDecimal;
Import java.util.ArrayList;
Import java.util.Collections;
Import Java.util.Comparator;

Import java.util.List; 

		public class Testsorting {public static void main (string[] args) {list<developer> Listdevs = Getdevelopers ();
		System.out.println ("before Sort");
		for (Developer Developer:listdevs) {System.out.println (Developer); //sort by Age Collections.sort (Listdevs, New comparator<developer> () {@Override public int compare (Dev
			Eloper O1, Developer O2) {return o1.getage ()-o2.getage ();

		}
		});
		System.out.println ("after Sort");
		for (Developer Developer:listdevs) {System.out.println (Developer); private static list<developer> Getdevelopers () {list<developer> result = new Arraylist<develope

		R> ();
		Result.add (New Developer ("Mkyong", New BigDecimal ("70000"), 33);
		Result.add (New Developer ("Alvin", New BigDecimal ("80000"), 20); Result.add (New Developer ("Jason", New BigDecimal ("100000"), 10);

		Result.add (New Developer ("Iris", New BigDecimal ("170000"), 55);

	return result; }

}

Output

Before Sort
Developer [Name=mkyong, salary=70000, age=33]
Developer [Name=alvin, salary=80000, age=20]
Developer [Name=jason, salary=100000, age=10]
Developer [Name=iris, salary=170000, age=55] after

Sort
Developer [Name=jason, salary=100000, age=10]
Developer [Name=alvin, salary=80000, age=20]
Developer [name= Mkyong, salary=70000, age=33]
Developer [Name=iris, salary=170000, age=55]

When the sort requirement changes, you can only implement it through a new anonymous class, as follows:

//sort by Age Collections.sort (Listdevs, New comparator<developer> () {@Override public int compare (Developer O1,
	Developer O2) {return o1.getage ()-o2.getage ();

}
});  Sort by name Collections.sort (Listdevs, New comparator<developer> () {@Override public int compare (Developer O1, Developer O2) {return o1.getname (