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| <div class="sub-title"><span class="package-label-in-type">Package</span> <a href="package-summary.html">org.apache.calcite.linq4j</a></div> |
| <h1 title="Class Extensions" class="title">Class Extensions</h1> |
| </div> |
| <div class="inheritance" title="Inheritance Tree"><a href="https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/lang/Object.html" title="class or interface in java.lang" class="external-link">java.lang.Object</a> |
| <div class="inheritance">org.apache.calcite.linq4j.Extensions</div> |
| </div> |
| <section class="class-description" id="class-description"> |
| <hr> |
| <div class="type-signature"><span class="modifiers">public abstract class </span><span class="element-name type-name-label">Extensions</span> |
| <span class="extends-implements">extends <a href="https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/lang/Object.html" title="class or interface in java.lang" class="external-link">Object</a></span></div> |
| <div class="block">Contains what, in LINQ.NET, would be extension methods. |
| |
| <h2>Notes on mapping from LINQ.NET to Java</h2> |
| |
| <p>We have preserved most of the API. But we've changed a few things, so that |
| the API is more typical Java API:</p> |
| |
| <ul> |
| |
| <li>Java method names start with a lower-case letter.</li> |
| |
| <li>A few methods became keywords when their first letter was converted |
| to lower case; hence |
| <a href="tree/Expressions.html#break_(org.apache.calcite.linq4j.tree.LabelTarget)"><code>Expressions.break_(org.apache.calcite.linq4j.tree.LabelTarget)</code></a></li> |
| |
| <li>We created a Java interface <a href="Enumerable.html" title="interface in org.apache.calcite.linq4j"><code>Enumerable</code></a>, similar to LINQ.NET's |
| IEnumerable. IEnumerable is built into C#, and that gives it |
| advantages: the standard collections implement it, and you can use |
| any IEnumerable in a foreach loop. We made the Java |
| <code>Enumerable</code> extend <a href="https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/lang/Iterable.html" title="class or interface in java.lang" class="external-link"><code>Iterable</code></a>, |
| so that it can be used in for-each loops. But the standard |
| collections still don't implement it. A few methods that take an |
| IEnumerable in LINQ.NET take an Iterable in LINQ4J.</li> |
| |
| <li>LINQ.NET's Dictionary interface maps to Map in Java; |
| hence, the LINQ.NET <code>ToDictionary</code> methods become |
| <code>toMap</code>.</li> |
| |
| <li>LINQ.NET's decimal type changes to BigDecimal. (A little bit unnatural, |
| since decimal is primitive and BigDecimal is not.)</li> |
| |
| <li>There is no Nullable in Java. Therefore we distinguish between methods |
| that return, say, Long (which may be null) and long. See for example |
| <a href="function/NullableLongFunction1.html" title="interface in org.apache.calcite.linq4j.function"><code>NullableLongFunction1</code></a> and |
| <a href="function/LongFunction1.html" title="interface in org.apache.calcite.linq4j.function"><code>LongFunction1</code></a>, and the |
| variants of <a href="ExtendedEnumerable.html#sum(org.apache.calcite.linq4j.function.BigDecimalFunction1)"><code>ExtendedEnumerable.sum(org.apache.calcite.linq4j.function.BigDecimalFunction1<TSource>)</code></a> that call them. |
| |
| <li>Java erases type parameters from argument types before resolving |
| overloading. Therefore similar methods have the same erasure. Methods |
| <code>averageDouble</code>, |
| <code>averageInteger</code>, |
| <code>groupByK</code>, |
| <code>selectN</code>, |
| <code>selectManyN</code>, |
| <code>skipWhileN</code>, |
| <code>sumBigDecimal</code>, |
| <code>sumNullableBigDecimal</code>, |
| <code>whereN</code> |
| have been renamed from <code>average</code>, <code>groupBy</code>, <code>max</code>, |
| <code>min</code>, <code>select</code>, <code>selectMany</code>, <code>skipWhile</code> and |
| <code>where</code> to prevent ambiguity.</li> |
| |
| <li>.NET allows <i>extension methods</i> — static methods that then |
| become, via compiler magic, a method of any object whose type is the |
| same as the first parameter of the extension method. In LINQ.NET, the |
| <code>IQueryable</code> and <code>IEnumerable</code> interfaces have many such methods. |
| In Java, those methods need to be explicitly added to the interface, and will |
| need to be implemented by every class that implements that interface. |
| We can help by implementing the methods as static methods, and by |
| providing an abstract base class that implements the extension methods |
| in the interface. Hence <a href="AbstractEnumerable.html" title="class in org.apache.calcite.linq4j"><code>AbstractEnumerable</code></a> and |
| <a href="AbstractQueryable.html" title="class in org.apache.calcite.linq4j"><code>AbstractQueryable</code></a> call methods in <a href="Extensions.html" title="class in org.apache.calcite.linq4j"><code>Extensions</code></a>.</li> |
| |
| <li>.NET Func becomes <a href="function/Function0.html" title="interface in org.apache.calcite.linq4j.function"><code>Function0</code></a>, |
| <a href="function/Function1.html" title="interface in org.apache.calcite.linq4j.function"><code>Function1</code></a>, |
| <a href="function/Function2.html" title="interface in org.apache.calcite.linq4j.function"><code>Function2</code></a>, depending |
| on the number of arguments to the function, because Java types cannot be |
| overloaded based on the number of type parameters.</li> |
| |
| <li>Types map as follows: |
| <code>Int32</code> → <code>int</code> or <a href="https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/lang/Integer.html" title="class or interface in java.lang" class="external-link"><code>Integer</code></a>, |
| <code>Int64</code> → <code>long</code> or <a href="https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/lang/Long.html" title="class or interface in java.lang" class="external-link"><code>Long</code></a>, |
| <code>bool</code> → <code>boolean</code> or <a href="https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/lang/Boolean.html" title="class or interface in java.lang" class="external-link"><code>Boolean</code></a>, |
| <code>Dictionary</code> → <a href="https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/util/Map.html" title="class or interface in java.util" class="external-link"><code>Map</code></a>, |
| <code>Lookup</code> → <a href="https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/util/Map.html" title="class or interface in java.util" class="external-link"><code>Map</code></a> whose value type is an <a href="https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/lang/Iterable.html" title="class or interface in java.lang" class="external-link"><code>Iterable</code></a>, |
| </li> |
| |
| <li>Function types that accept primitive types in LINQ.NET have become |
| boxed types in LINQ4J. For example, a predicate function |
| <code>Func<T, bool></code> becomes <code>Func1<T, Boolean></code>. |
| It would be wrong to infer that the function is allowed to return null.</li> |
| |
| </ul></div> |
| </section> |
| <section class="summary"> |
| <ul class="summary-list"> |
| <!-- ========== METHOD SUMMARY =========== --> |
| <li> |
| <section class="method-summary" id="method-summary"> |
| <h2>Method Summary</h2> |
| <div id="method-summary-table"> |
| <div class="table-tabs" role="tablist" aria-orientation="horizontal"><button id="method-summary-table-tab0" role="tab" aria-selected="true" aria-controls="method-summary-table.tabpanel" tabindex="0" onkeydown="switchTab(event)" onclick="show('method-summary-table', 'method-summary-table', 3)" class="active-table-tab">All Methods</button><button id="method-summary-table-tab1" role="tab" aria-selected="false" aria-controls="method-summary-table.tabpanel" tabindex="-1" onkeydown="switchTab(event)" onclick="show('method-summary-table', 'method-summary-table-tab1', 3)" class="table-tab">Static Methods</button><button id="method-summary-table-tab4" role="tab" aria-selected="false" aria-controls="method-summary-table.tabpanel" tabindex="-1" onkeydown="switchTab(event)" onclick="show('method-summary-table', 'method-summary-table-tab4', 3)" class="table-tab">Concrete Methods</button></div> |
| <div id="method-summary-table.tabpanel" role="tabpanel"> |
| <div class="summary-table three-column-summary" aria-labelledby="method-summary-table-tab0"> |
| <div class="table-header col-first">Modifier and Type</div> |
| <div class="table-header col-second">Method</div> |
| <div class="table-header col-last">Description</div> |
| <div class="col-first even-row-color method-summary-table method-summary-table-tab1 method-summary-table-tab4"><code>static <T> <a href="Queryable.html" title="interface in org.apache.calcite.linq4j">Queryable</a><T></code></div> |
| <div class="col-second even-row-color method-summary-table method-summary-table-tab1 method-summary-table-tab4"><code><a href="#asQueryable(org.apache.calcite.linq4j.DefaultEnumerable)" class="member-name-link">asQueryable</a><wbr>(<a href="DefaultEnumerable.html" title="class in org.apache.calcite.linq4j">DefaultEnumerable</a><T> source)</code></div> |
| <div class="col-last even-row-color method-summary-table method-summary-table-tab1 method-summary-table-tab4"> </div> |
| <div class="col-first odd-row-color method-summary-table method-summary-table-tab1 method-summary-table-tab4"><code>static <a href="https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/lang/RuntimeException.html" title="class or interface in java.lang" class="external-link">RuntimeException</a></code></div> |
| <div class="col-second odd-row-color method-summary-table method-summary-table-tab1 method-summary-table-tab4"><code><a href="#todo()" class="member-name-link">todo</a>()</code></div> |
| <div class="col-last odd-row-color method-summary-table method-summary-table-tab1 method-summary-table-tab4"> </div> |
| </div> |
| </div> |
| </div> |
| <div class="inherited-list"> |
| <h3 id="methods-inherited-from-class-java.lang.Object">Methods inherited from class java.lang.<a href="https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/lang/Object.html" title="class or interface in java.lang" class="external-link">Object</a></h3> |
| <code><a href="https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/lang/Object.html#clone()" title="class or interface in java.lang" class="external-link">clone</a>, <a href="https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/lang/Object.html#equals(java.lang.Object)" title="class or interface in java.lang" class="external-link">equals</a>, <a href="https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/lang/Object.html#finalize()" title="class or interface in java.lang" class="external-link">finalize</a>, <a href="https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/lang/Object.html#getClass()" title="class or interface in java.lang" class="external-link">getClass</a>, <a href="https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/lang/Object.html#hashCode()" title="class or interface in java.lang" class="external-link">hashCode</a>, <a href="https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/lang/Object.html#notify()" title="class or interface in java.lang" class="external-link">notify</a>, <a href="https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/lang/Object.html#notifyAll()" title="class or interface in java.lang" class="external-link">notifyAll</a>, <a href="https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/lang/Object.html#toString()" title="class or interface in java.lang" class="external-link">toString</a>, <a href="https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/lang/Object.html#wait()" title="class or interface in java.lang" class="external-link">wait</a>, <a href="https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/lang/Object.html#wait(long)" title="class or interface in java.lang" class="external-link">wait</a>, <a href="https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/lang/Object.html#wait(long,int)" title="class or interface in java.lang" class="external-link">wait</a></code></div> |
| </section> |
| </li> |
| </ul> |
| </section> |
| <section class="details"> |
| <ul class="details-list"> |
| <!-- ============ METHOD DETAIL ========== --> |
| <li> |
| <section class="method-details" id="method-detail"> |
| <h2>Method Details</h2> |
| <ul class="member-list"> |
| <li> |
| <section class="detail" id="todo()"> |
| <h3>todo</h3> |
| <div class="member-signature"><span class="modifiers">public static</span> <span class="return-type"><a href="https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/lang/RuntimeException.html" title="class or interface in java.lang" class="external-link">RuntimeException</a></span> <span class="element-name">todo</span>()</div> |
| </section> |
| </li> |
| <li> |
| <section class="detail" id="asQueryable(org.apache.calcite.linq4j.DefaultEnumerable)"> |
| <h3>asQueryable</h3> |
| <div class="member-signature"><span class="modifiers">public static</span> <span class="type-parameters"><T></span> <span class="return-type"><a href="Queryable.html" title="interface in org.apache.calcite.linq4j">Queryable</a><T></span> <span class="element-name">asQueryable</span><wbr><span class="parameters">(<a href="DefaultEnumerable.html" title="class in org.apache.calcite.linq4j">DefaultEnumerable</a><T> source)</span></div> |
| </section> |
| </li> |
| </ul> |
| </section> |
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