Database System Concepts
Database System Concepts
7th Edition
ISBN: 9780078022159
Author: Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan
Publisher: McGraw-Hill Education
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Java Programming: There is an error in the code so make sure to fix it:

OrderedMergeIterator.java

import java.util.Iterator;
import java.util.Map;
import java.util.PriorityQueue;
import java.util.Queue;

public class OrderedMergeIterator<DataElement extends Comparable<? super DataElement>> implements Iterator<DataElement> {
private Queue<Map.Entry<DataElement, Iterator<DataElement>>> queue;

public OrderedMergeIterator(Iterator<DataElement>... iterators) {
queue = new PriorityQueue<>((entry1, entry2) -> entry1.getKey().compareTo(entry2.getKey()));

for (Iterator<DataElement> iterator : iterators) {
if (iterator.hasNext()) {
DataElement element = iterator.next();
queue.add(Map.entry(element, iterator));
}
}
}

@Override
public boolean hasNext() {
return !queue.isEmpty();
}

@Override
public DataElement next() {
if (hasNext()) {
Map.Entry<DataElement, Iterator<DataElement>> entry = queue.poll();
DataElement element = entry.getKey();
Iterator<DataElement> iterator = entry.getValue();

if (iterator.hasNext()) {
DataElement nextElement = iterator.next();
queue.add(Map.entry(nextElement, iterator));
}

return element;
}

throw new RuntimeException("No more elements in the merge iterator");
}
}

Attached is an image of the errors:

[画像:110 12 13 14 15 16 17 18 19 20 21 220 423 24 25 26 270 -28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44} 45 public Ordered MergeIterator (Iterator<Data Element>... iterators) { queue = new PriorityQueue<> ((entry1, entry2) -> entry1.getKey().compareTo(entry2.getKey())); } } for (Iterator<Data Element> iterator: iterators) { if (iterator.hasNext()) { Data Element element iterator.next(); queue.add(Map.entry(element, iterator)); } @Override public boolean hasNext() { return !queue.isEmpty(); } } @Override public Data Element next() { if (hasNext()) { } Map.Entry<Data Element, Iterator<DataElement>> entry = queue.poll(); Data Element element = entry.getKey(); Iterator<DataElement> iterator = entry.getValue(); if (iterator.hasNext()) { Data Element nextElement = iterator.next(); queue.add(Map entry nextElement, iterator)); } return element; throw new RuntimeException ("No more elements in the merge iterator");]
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Transcribed Image Text:110 12 13 14 15 16 17 18 19 20 21 220 423 24 25 26 270 -28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44} 45 public Ordered MergeIterator (Iterator<Data Element>... iterators) { queue = new PriorityQueue<> ((entry1, entry2) -> entry1.getKey().compareTo(entry2.getKey())); } } for (Iterator<Data Element> iterator: iterators) { if (iterator.hasNext()) { Data Element element iterator.next(); queue.add(Map.entry(element, iterator)); } @Override public boolean hasNext() { return !queue.isEmpty(); } } @Override public Data Element next() { if (hasNext()) { } Map.Entry<Data Element, Iterator<DataElement>> entry = queue.poll(); Data Element element = entry.getKey(); Iterator<DataElement> iterator = entry.getValue(); if (iterator.hasNext()) { Data Element nextElement = iterator.next(); queue.add(Map entry nextElement, iterator)); } return element; throw new RuntimeException ("No more elements in the merge iterator");
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