Class LambdaExamples

java.lang.Object

net.jrodolfo.java_evolution.java08.LambdaExamples

public class LambdaExamples
extends Object

Demonstrates lambda expressions, one of the main language features introduced in Java 8.

Before Java 8, passing behavior into a method usually meant creating an anonymous class. That made common operations such as filtering, sorting, and callbacks much more verbose than the actual idea being expressed.

Lambdas solve this by letting Java treat a small block of behavior as a value, as long as the target type is a functional interface. They are commonly used with interfaces such as Predicate, Comparator, and the interfaces in java.util.function. This also made the Stream API practical because stream operations can receive behavior directly.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static interface	LambdaExamples.IntegerOperation	Simple functional interface used to demonstrate passing behavior into a method.

Constructor Summary

Constructors

Constructor	Description
LambdaExamples()

Method Summary

Modifier and Type	Method	Description
int	calculate(int left, int right, LambdaExamples.IntegerOperation operation)	Receives a custom operation as a method argument.
List<String>	namesWithAtLeastFourLetters(List<String> names)	Filters a list by assigning a lambda expression to a Predicate.
int	normalizedPositiveDifference(int left, int right)	Uses a multi-statement lambda body.
List<String>	sortByLength(List<String> names)	Sorts names using a lambda expression as a Comparator.
List<String>	sortWithAnonymousClass(List<String> names)	Sorts names with an anonymous class, the older style commonly used before Java 8 lambdas.
List<String>	sortWithLambda(List<String> names)	Sorts names with a lambda expression, showing the shorter Java 8 replacement for a simple anonymous class.

Methods inherited from class Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details

LambdaExamples

public LambdaExamples()

Method Details

namesWithAtLeastFourLetters

public List<String> namesWithAtLeastFourLetters(List<String> names)

Filters a list by assigning a lambda expression to a Predicate.

Parameters:

names - the names to inspect

Returns:

only the names that contain at least four letters

sortByLength

public List<String> sortByLength(List<String> names)

Sorts names using a lambda expression as a Comparator.

Parameters:

names - the names to sort

Returns:

a new list sorted from shortest name to longest name

calculate

public int calculate(int left,
 int right,
 LambdaExamples.IntegerOperation operation)

Receives a custom operation as a method argument.

Parameters:

left - the left number used by the operation

right - the right number used by the operation

operation - the behavior to apply to both numbers

Returns:

the result produced by the operation

normalizedPositiveDifference

public int normalizedPositiveDifference(int left,
 int right)

Uses a multi-statement lambda body.

Single-expression lambdas can omit braces and return. When the lambda needs more than one statement, Java requires a block body and an explicit return for non-void functional interfaces.

Parameters:

left - the left number used by the operation

right - the right number used by the operation

Returns:

a normalized score

sortWithAnonymousClass

public List<String> sortWithAnonymousClass(List<String> names)

Sorts names with an anonymous class, the older style commonly used before Java 8 lambdas.

Parameters:

names - the names to sort

Returns:

a new list sorted alphabetically

sortWithLambda

public List<String> sortWithLambda(List<String> names)

Sorts names with a lambda expression, showing the shorter Java 8 replacement for a simple anonymous class.

Parameters:

names - the names to sort

Returns:

a new list sorted alphabetically