110 lines
4.0 KiB
Java
110 lines
4.0 KiB
Java
package net.abhinavsarkar.spelhelper;
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import static java.util.Collections.unmodifiableList;
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import static java.util.Collections.unmodifiableSet;
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import java.util.ArrayList;
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import java.util.Collections;
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import java.util.HashSet;
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import java.util.List;
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import java.util.Set;
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/**
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* Provides some implicit methods which can be invoked on the instances of
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* class of the first parameter of the method inside a SpEL expression.
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* @author Abhinav Sarkar _abhinav@abhinavsarkar.net_
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*/
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public final class ImplicitMethods {
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/**
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* Provides implicit method `distinct` on the {@link List} class.
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*
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* Example: `"#list('a','b','a').distinct()" //should return List('a','b')`
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*
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* With implicit property support provided by {@link SpelHelper} this can
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* also be written as:
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*
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* `"#list('a','b','a').distinct" //same output as earlier`
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* @param <T> Type of the list's elements.
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* @param list The list to call this method upon.
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* @return An unmodifiable {@link Set} containing the distinct items of the list.
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*/
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public static <T> Set<T> distinct(final List<? extends T> list) {
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return unmodifiableSet(new HashSet<T>(list));
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}
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/**
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* Provides implicit method `sorted` on the {@link List} class.
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*
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* Example: `"#list('c','b','a').sorted()" //should return List('a','b','c')`
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*
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* With implicit property support provided by {@link SpelHelper} this can
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* also be written as:
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*
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* `"#list('c','b','a').sorted" //same output as earlier`
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* @param <T> Type of the list's elements.
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* @param list The list to call this method upon.
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* @return An unmodifiable {@link List} containing the sorted items
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* of the list.
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* @see Collections#sort(List)
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*/
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public static <T extends Comparable<? super T>> List<T> sorted(
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final List<? extends T> list) {
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List<T> temp = new ArrayList<T>(list);
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Collections.sort(temp);
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return unmodifiableList(temp);
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}
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/**
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* Provides implicit method `reversed` on the {@link List} class.
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*
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* Example: `"#list('c','b','a').reversed()" //should return List('a','b','c')`
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*
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* With implicit property support provided by {@link SpelHelper} this can
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* also be written as:
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*
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* `"#list('c','b','a').reversed" //same output as earlier`
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* @param <T> Type of the list's elements.
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* @param list The list to call this method upon.
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* @return An unmodifiable {@link List} containing the items of the
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* list in reverse order.
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* @see Collections#reverse(List)
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*/
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public static <T> List<T> reversed(final List<? extends T> list) {
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List<T> temp = new ArrayList<T>(list);
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Collections.reverse(temp);
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return unmodifiableList(temp);
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}
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/**
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* Provides implicit method `take` on the {@link List} class.
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*
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* Example: `"#list('c','b','a').take(2)" //should return List('a','b')`
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*
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* @param <T> Type of the list's elements.
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* @param list The list to call this method upon.
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* @param n Number of items to _take_ from the list.
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* @return An unmodifiable {@link List} containing the first `n` items
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* of the list.
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*/
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public static <T> List<T> take(final List<T> list, final int n) {
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return unmodifiableList(list.subList(0, n));
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}
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/**
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* Provides implicit method `drop` on the {@link List} class.
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*
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* Example: `"#list('c','b','a').drop(2)" //should return List('a')`
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*
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* @param <T> Type of the list's elements.
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* @param list The list to call this method upon.
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* @param n Number of items to _drop_ from the list.
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* @return An unmodifiable {@link List} containing the items after the
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* first `n` items of the list.
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*/
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public static <T> List<T> drop(final List<T> list, final int n) {
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return unmodifiableList(list.subList(n, list.size()));
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}
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}
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