Answered: Java Programming: There is an error in…

Database System Concepts

7th Edition

ISBN:9780078022159

Author:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan

Publisher:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan

Chapter1: Introduction

Section: Chapter Questions

Problem 1PE

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Question

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:

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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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