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Convenient utility to build XML models by evaluating XPath expressions
There is a newer version: 2.3.9
package com.github.simy4.xpath.view;

import com.github.simy4.xpath.XmlBuilderException;
import com.github.simy4.xpath.navigator.Node;
import com.github.simy4.xpath.util.FilteringIterator;
import com.github.simy4.xpath.util.Function;
import com.github.simy4.xpath.util.Predicate;
import com.github.simy4.xpath.util.TransformingIterator;

import java.util.Collections;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Set;

public final class NodeSetView implements IterableNodeView {

    private static final NodeSetView EMPTY_NODE_SET = new NodeSetView(Collections.>emptySet());

    @SuppressWarnings("unchecked")
    public static  NodeSetView empty() {
        return (NodeSetView) EMPTY_NODE_SET;
    }

    private final Iterable> nodeSet;

    /**
     * Creates NodeSetView from given nodes and predicate.
     *
     * @param nodes     nodes to wap in a view
     * @param predicate predicate to apply to nodes
     */
    public NodeSetView(final Iterable nodes, final Predicate predicate) {
        this(new Iterable>() {
            @Override
            public Iterator> iterator() {
                return new TransformingIterator>(new FilteringIterator(nodes.iterator(), predicate),
                        new NodeWrapper());
            }
        });
    }

    public NodeSetView(Iterable> nodeSet) {
        this.nodeSet = nodeSet;
    }

    @Override
    public int compareTo(View other) {
        final Iterator> iterator = iterator();
        if (iterator.hasNext()) {
            return iterator.next().compareTo(other);
        } else {
            return other.toBoolean() ? -1 : 0;
        }
    }

    @Override
    public boolean toBoolean() {
        return iterator().hasNext();
    }

    @Override
    public double toNumber() {
        final Iterator> iterator = iterator();
        return iterator.hasNext() ? iterator.next().toNumber() : Double.NaN;
    }

    @Override
    public String toString() {
        final Iterator> iterator = iterator();
        return iterator.hasNext() ? iterator.next().toString() : "";
    }

    @Override
    public  T visit(ViewVisitor visitor) throws XmlBuilderException {
        return visitor.visit(this);
    }

    @Override
    public Iterator> iterator() {
        return new FilteringIterator>(nodeSet.iterator(), new Distinct());
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) {
            return true;
        }
        if (!(o instanceof View)) {
            return false;
        }

        final Iterator> iterator = iterator();
        if (iterator.hasNext()) {
            return iterator.next().equals(o);
        } else {
            return !((View) o).toBoolean();
        }
    }

    @Override
    public int hashCode() {
        final Iterator> iterator = iterator();
        return iterator.hasNext() ? iterator.next().hashCode() : 0;
    }

    private static final class NodeWrapper implements Function> {

        @Override
        public NodeView apply(T node) {
            return new NodeView(node);
        }

    }

    private static final class Distinct implements Predicate> {

        private final Set visited = new HashSet();

        @Override
        public boolean test(NodeView node) {
            return visited.add(node.getNode());
        }

    }

}