io.inbot.utils

Class PatternEvaluator<Input,Output>

java.lang.Object

io.inbot.utils.PatternEvaluator<Input,Output>

Type Parameters:

Input - Input

Output - Output

public class PatternEvaluator<Input,Output>
extends Object

Simple Java lambda based implementation of Kotlin and Scala style pattern matching. This provides a nice alternative to the if else chaos that and a more powerful alternative to switch statements. It's not perfect of course but it should allow for some limited verbosity when doing this kind of stuff. Inspired by https://kerflyn.wordpress.com/2012/05/09/towards-pattern-matching-in-java/. Because the evaluate returns an Optional, you can emulate the otherwise bit with a simple call to orElse(...).

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	PatternEvaluator.BoolExprPattern<I,O> If you want to match using a lambda function that produces a boolean this is what you use.
static class	PatternEvaluator.EqualsPattern<I,O> Allows you to produce patterns that simply compare the input to the value and produce the output when they are equal.

Constructor Summary

Constructors

Constructor and Description
PatternEvaluator(io.inbot.utils.PatternEvaluator.Pattern<Input,Output>... ps)

Method Summary

Modifier and Type	Method and Description
static <I,O> PatternEvaluator.EqualsPattern<I,O>	equals(I value, java.util.function.Function<I,O> f) Allows you to match on a value using the equals method
Optional<Output>	evaluate(Input matchVal)
static <I,O> Optional<O>	evaluate(I input, io.inbot.utils.PatternEvaluator.Pattern<I,O>... patterns) Creates an evaluator and then evaluates the value right away.
static <I,O> PatternEvaluator<I,O>	evaluator(io.inbot.utils.PatternEvaluator.Pattern<I,O>... patterns)
static <I,O> PatternEvaluator.BoolExprPattern<I,O>	matches(java.util.function.Function<I,Boolean> expr, java.util.function.Function<I,O> f) Allows you use a lambda to match on an input.

Methods inherited from class java.lang.Object

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

Constructor Detail

PatternEvaluator

@SafeVarargs
public PatternEvaluator(io.inbot.utils.PatternEvaluator.Pattern<Input,Output>... ps)

Method Detail

evaluate

public Optional<Output> evaluate(Input matchVal)

matches

public static <I,O> PatternEvaluator.BoolExprPattern<I,O> matches(java.util.function.Function<I,Boolean> expr,
                                                                  java.util.function.Function<I,O> f)

Allows you use a lambda to match on an input.

Type Parameters:

I - Input

O - Output

Parameters:

expr - expression that evaluates to true/false

f - function that produces O from I

Returns:

pattern that matches on the expression

equals

public static <I,O> PatternEvaluator.EqualsPattern<I,O> equals(I value,
                                                               java.util.function.Function<I,O> f)

Allows you to match on a value using the equals method

Type Parameters:

I - Input

O - Output

Parameters:

value - the object to compare I to

f - function that produces O from I

Returns:

O

evaluator

@SafeVarargs
public static <I,O> PatternEvaluator<I,O> evaluator(io.inbot.utils.PatternEvaluator.Pattern<I,O>... patterns)

Type Parameters:

I - Input

O - Output

Parameters:

patterns - zero or more patterns

Returns:

evaluator for the given patterns

evaluate

@SafeVarargs
public static <I,O> Optional<O> evaluate(I input,
                                                      io.inbot.utils.PatternEvaluator.Pattern<I,O>... patterns)

Creates an evaluator and then evaluates the value right away.

Type Parameters:

I - Input

O - Output

Parameters:

input - input value

patterns - zero or more patterns

Returns:

O