Java/Lambas - Revision history

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2017-07-05T23:57:07Z

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2017-07-05T23:56:35Z

References

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	Oracle Java tutorial on lambda expressions: http://docs.oracle.com/javase/tutorial/java/javaOO/lambdaexpressions.html		Oracle Java tutorial on lambda expressions: http://docs.oracle.com/javase/tutorial/java/javaOO/lambdaexpressions.html



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Admin: /* Lambdas for Comparators */

2017-07-05T23:55:57Z

Lambdas for Comparators

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 ===Comparator Examples===
-insert here.
+Compare by x coordinates (if x coordinates are equal, the points are equal):
 ==References==
 Oracle Java tutorial on lambda expressions: http://docs.oracle.com/javase/tutorial/java/javaOO/lambdaexpressions.html

Admin: /* Lambdas for Comparators */

2017-07-05T23:48:45Z

Lambdas for Comparators

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 </pre>
-Now suppose we want to sort point objects by their x coordinates only (ignoring y coordinates). We start by defining a Comparator object that wraps Point objects: <code>Comparator<Point> pc</code>.
+Now suppose we want to sort a list of Point objects, using some kind of custom criteria. We could have Point extend Comparable, and define a compareTo() method, so that we could perform a direct comparison with two point objects. But suppose I have many criteria, and I don't have any control over the Point object source code, so I can't modify the class definition. In this situation I can use a Comparator object, which defines a compare() method taking two objects, performs some calculation, and returns an integer result (analogous to the result that a compareTo method would return).
-	Comparator<Developer> byName =
+We will demonstrate with some lambda Comparator examples. here is the framework:
 ==References==
 Oracle Java tutorial on lambda expressions: http://docs.oracle.com/javase/tutorial/java/javaOO/lambdaexpressions.html

Admin: Created page with "==Lambda Expressions== When it comes to dealing with functions as first-class objects in the language, Java is much more limited than Python. In fact, it was not until Java 8..."

2017-07-05T22:38:27Z

Created page with "==Lambda Expressions== When it comes to dealing with functions as first-class objects in the language, Java is much more limited than Python. In fact, it was not until Java 8..."

New page

==Lambda Expressions==

When it comes to dealing with functions as first-class objects in the language, Java is much more limited than Python. In fact, it was not until Java 8 that Java finally got lambda expressions, which are ways of defining functions using in-place, shorthand expressions.

==Lambdas for Comparators==

You can throw together a fast comparator with a single lambda function, by skipping the class definition and the compare method, and simply using a lambda function instead.

Suppose I have a simple Point object storing two elements:

<pre>
public class Point {
public int x, y;
public Point(int x0, int y0) { this.x = x0; this.y = y0; }
public String tString() { return "("+this.x+","+this.y+")";}
}
</pre>

Now suppose we want to sort point objects by their x coordinates only (ignoring y coordinates). We start by defining a Comparator object that wraps Point objects: <code>Comparator<Point> pc</code>.

Comparator<Developer> byName =
(Developer o1, Developer o2)->o1.getName().compareTo(o2.getName());

==References==

Oracle Java tutorial on lambda expressions: http://docs.oracle.com/javase/tutorial/java/javaOO/lambdaexpressions.html