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Merge pull request #6 from dykov/add-next-method
Add '.next' method
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‎readme.md‎

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@@ -32,6 +32,7 @@
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* [.find](#find)
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* [.reduce](#reduce)
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* [.after](#after)
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* [.next](#next)
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* [How to contribute?](#how-to-contribute)
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@@ -185,6 +186,27 @@ public interface Enumerable<X> extends Collection<X> {
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default Enumerable<X> after(Predicate<X> prd, long size) {
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// ...
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}
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/**
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* Returns the next element of enumerable after the first one which corresponds the condition.
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* If no predicate (null) is given, or no element found then alternative is returned instead.
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* @param prd The function to match element after which enumerable element should be returned.
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* @return The next element of enumerable after the first one which corresponds the condition.
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*/
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default X next(Predicate<X> prd) {
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// ...
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}
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/**
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* Returns the next element of enumerable after the first one which corresponds the condition.
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* If no predicate (null) is given, or no element found then alternative is returned instead.
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* @param prd The function to match element after which enumerable element should be returned.
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* @param alt The alternative to return in case of null predicate or no element found.
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* @return The next element of enumerable after the first one which corresponds the condition.
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*/
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default X next(Predicate<X> prd, X alt) {
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// ...
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}
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}
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```
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See [more](./src/main/java/io/github/dgroup/enumerable4j/Enumerable.java).
@@ -225,6 +247,7 @@ See [more](./src/main/java/io/github/dgroup/enumerable4j/Enumerable.java).
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`.find(...)` | `.stream().filter(...).findFirst().orElse(...)` | `new FirstOf<>(...,...).value()` | tbd |
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`.reduce(...,...)` | `.stream().reduce(...,...)` | `new Reduced<>(...,...).value()` | tbd |
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`.after(...)` | | | tbd |
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`.next(...)` | | | tbd |
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#### .all
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@@ -297,6 +320,13 @@ YourOwnCollection<Integer> src = ... // with
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Enumerable<Integer> afterThree = src.after(val -> val == 3); // [4, 5, 6]
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Enumerable<Integer> firstTwoAfterThree = src.after(val -> val == 3, 2); // [4, 5]
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```
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#### .next
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```java
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YourOwnCollection<Integer> src = ... // with elements [1, 2, 3, 4]
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Integer next = src.next(val -> val == 2); // 3
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Integer alternative = src.next(val -> val > 5, -1); // -1
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```
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### How to contribute?
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‎src/main/java/io/github/dgroup/enumerable4j/Enumerable.java‎

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@@ -258,4 +258,32 @@ default Enumerable<X> after(Predicate<X> prd, long size) {
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}
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return out;
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}
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/**
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* Returns the next element of enumerable after the first one which corresponds the condition.
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* If no predicate (null) is given, or no element found then null is returned instead.
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* @param prd The function to match element after which enumerable element should be returned.
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* @return The next element of enumerable after the first one which corresponds the condition.
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*/
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default X next(Predicate<X> prd) {
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return this.next(prd, null);
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}
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/**
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* Returns the next element of enumerable after the first one which corresponds the condition.
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* If no predicate (null) is given, or no element found then alternative is returned instead.
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* @param prd The function to match element after which enumerable element should be returned.
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* @param alt The alternative to return in case of null predicate or no element found.
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* @return The next element of enumerable after the first one which corresponds the condition.
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*/
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default X next(Predicate<X> prd, X alt) {
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final X out;
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if (prd == null) {
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out = alt;
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} else {
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out = this.after(prd, 1).stream().findFirst().orElse(alt);
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}
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return out;
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}
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}

‎src/test/java/io/github/dgroup/enumerable4j/FindTest.java‎

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@@ -50,7 +50,7 @@ void find() {
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@Test
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void nullPredicate() {
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new Assertion<>(
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"In case of null predicate we will get the same enumerable",
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"In case of the null predicate, we get null as a result",
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new Linked<>(1, 2, 3).find(null),
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new IsNull<>()
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).affirm();

‎src/test/java/io/github/dgroup/enumerable4j/NextTest.java‎

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/*
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* MIT License
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*
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* Copyright (c) 2019-2021 Yurii Dubinka
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"),
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* to deal in the Software without restriction, including without limitation
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* the rights to use, copy, modify, merge, publish, distribute, sublicense,
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* and/or sell copies of the Software, and to permit persons to whom
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* the Software is furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included
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* in all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
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* ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE
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* OR OTHER DEALINGS IN THE SOFTWARE.
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*/
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package io.github.dgroup.enumerable4j;
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import org.hamcrest.core.IsEqual;
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import org.hamcrest.core.IsNull;
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import org.junit.jupiter.api.Test;
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import org.llorllale.cactoos.matchers.Assertion;
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/**
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* Test cases for {@link Enumerable#next}.
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*
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* @since 0.1.0
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* @checkstyle MagicNumberCheck (500 lines)
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* @checkstyle JavadocMethodCheck (500 lines)
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*/
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@SuppressWarnings("PMD.AvoidDuplicateLiterals")
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public class NextTest {
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@Test
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void nullPredicate() {
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new Assertion<>(
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"In a case of the null predicate, we get null as a result",
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new Linked<>(1, 2, 3).next(null),
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new IsNull<>()
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).affirm();
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}
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@Test
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void altNullPredicate() {
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new Assertion<>(
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"In a case of the null predicate, we get an alternative result",
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new Linked<>(1, 2, 3).next(null, -1),
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new IsEqual<>(-1)
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).affirm();
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}
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@Test
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void getNext() {
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new Assertion<>(
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"Returns the next element after the first one which corresponds the condition",
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new Linked<>(1, 2, 3, 4, 5).next(n -> n > 1),
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new IsEqual<>(3)
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).affirm();
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}
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@Test
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void altGetNext() {
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new Assertion<>(
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"Returns the next element after the first one which corresponds the condition",
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new Linked<>(1, 2, 3, 4, 5).next(n -> n > 1, -1),
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new IsEqual<>(3)
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).affirm();
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}
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@Test
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void noneMatch() {
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new Assertion<>(
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"No one element corresponds the condition, the result is null",
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new Linked<>(1, 2, 3).next(n -> n > 10),
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new IsNull<>()
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).affirm();
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}
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@Test
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void altNoneMatch() {
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new Assertion<>(
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"No one element corresponds the condition, we get an alternative result",
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new Linked<>(1, 2, 3).next(n -> n > 10, -1),
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new IsEqual<>(-1)
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).affirm();
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}
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}

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