103 lines
2.7 KiB
Java
103 lines
2.7 KiB
Java
package org.warp.commonutils.type;
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import it.unimi.dsi.fastutil.objects.ObjectLinkedOpenHashSet;
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import java.util.ArrayList;
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import java.util.LinkedHashSet;
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import java.util.List;
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import java.util.NoSuchElementException;
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import org.warp.commonutils.error.IndexOutOfBoundsException;
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/**
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* A stack but with the behavior of a Linked HashSet
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*
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* <p>A stack must provide the classical {@link #push(Object)} and
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* {@link #pop()} operations, but may be also <em>peekable</em> to some extent: it may provide just the {@link #top()}
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* function, or even a more powerful {@link #peek(int)} method that provides access to all elements on the stack
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* (indexed from the top, which has index 0).
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*/
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public interface StackSet<K> {
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/**
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* Pushes the given object on the stack.
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*
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* @param o the object that will become the new top of the stack.
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* @return true if added, false if already present
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*/
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boolean push(K o);
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/**
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* Pop multiple times
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* @param count the number of times to pop
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* @return list of popped elements
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*/
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default List<K> pop(int count) {
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if (count < 0) {
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throw new IndexOutOfBoundsException(count);
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}
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var items = new ArrayList<K>(count);
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for (int i = 0; i < count; i++) {
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items.add(this.pop());
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}
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return items;
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}
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/**
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* Pops the top off the stack.
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*
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* @return the top of the stack.
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* @throws NoSuchElementException if the stack is empty.
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*/
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K pop();
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/**
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* Checks whether the stack is empty.
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*
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* @return true if the stack is empty.
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*/
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boolean isEmpty();
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/**
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* Peeks at the top of the stack (optional operation).
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*
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* <p>This default implementation returns {@link #peek(int) peek(0)}.
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*
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* @return the top of the stack.
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* @throws NoSuchElementException if the stack is empty.
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*/
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default K top() {
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return peek(0);
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}
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/**
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* Peeks at an element on the stack (optional operation).
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*
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* <p>This default implementation just throws an {@link UnsupportedOperationException}.
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*
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* @param i an index from the stop of the stack (0 represents the top).
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* @return the {@code i}-th element on the stack.
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* @throws IndexOutOfBoundsException if the designated element does not exist..
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*/
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default K peek(int i) {
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throw new UnsupportedOperationException();
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}
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static <T> StackSet<T> create() {
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return new HashStackSet<>();
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}
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static <T> StackSet<T> wrap(LinkedHashSet<T> linkedHashSet) {
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return new JavaStackSetWrapper<>(linkedHashSet);
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}
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static <T> StackSet<T> wrap(ObjectLinkedOpenHashSet<T> linkedHashSet) {
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return new FastUtilStackSetWrapper<>(linkedHashSet);
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}
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static <T> StackSet<T> wrap(ObjectLinkedOpenHashSet<T> linkedHashSet, AddStrategy addStrategy) {
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return new FastUtilStackSetWrapper<>(linkedHashSet, addStrategy);
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}
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}
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