can anyone help

Question about the task

Shortener (10)

Java Collections, Level 6, Lesson 15

Resolved

am getting NPE line 153 and every where where trying to get from FileBucket obj the Entry thank u!

Create and implement a FileStorageStrategy class. It must:
10.1. Implement the StorageStrategy interface.
10.2. Use FileBucket as a buckets.

Hint: The class must have a FileBucket[] table field.

10.3. It works like OurHashMapStorageStrategy, but double the number of buckets not when the number of size elements becomes larger than some threshold, but rather when the size of one of the buckets (files) became larger than bucketSizeLimit.
10.3.1. Add a long bucketSizeLimit field to the class.
10.3.2. Initialize it with a default value, such as 10,000 bytes.
10.3.3. Add a setter and getter for this field.
10.4. When implementing the resize(int newCapacity) method, be sure that the files you no longer need have been deleted (call the remove() method).
Test the new strategy in the main() method. Bear in mind that the FileStorageStrategy strategy is much slower than the others. Don't use a large number of elements for the test. Doing so could take a looooog time. Run the program and compare the performance of all 3 strategies.

P.S. Be sure that the FileStorageStrategy class has all the necessary fields by analogy with OurHashMapStorageStrategy:
static final int DEFAULT_INITIAL_CAPACITY
static final long DEFAULT_BUCKET_SIZE_LIMIT
FileBucket[] table
int size
private long bucketSizeLimit = DEFAULT_BUCKET_SIZE_LIMIT
long maxBucketSize

Requirements:

The FileStorageStrategy class must support the StorageStrategy interface.
All the required fields (according to the task conditions) must be created in the FileStorageStrategy class.
The StorageStrategy interface's methods must be implemented in FileStorageStrategy in a way that ensures the correct operation of the Shortener class on which it is based.

package com.codegym.task.task33.task3310; import com.codegym.task.task33.task3310.strategy.*; import java.util.*; public class Solution { public static Set<Long> getIds(Shortener shortener, Set<String> strings) { Set<Long> set = new HashSet<>(); for (String str : strings) { set.add(shortener.getId(str)); } return set; } public static Set<String> getStrings(Shortener shortener, Set<Long> keys) { Set<String> set = new HashSet<>(); for (Long l : keys) { set.add(shortener.getString(l)); } return set; } public static void testStrategy(StorageStrategy strategy, long elementsNumber) { Helper.printMessage(strategy.getClass().getSimpleName()); Set<String> set = new HashSet<>(); Set<Long> set2 = new HashSet<>(); Set<String> set3 = new HashSet<>(); for (int i = 0; i < elementsNumber; i++) { String testString = Helper.generateRandomString(); set.add(testString); } Shortener sr = new Shortener(strategy); Date startD = new Date(); for (String string : set) { set2.add(sr.getId(string)); } Helper.printMessage(new Date().getTime() - startD.getTime() + ""); startD = new Date(); for (Long long1 : set2) { set3.add(sr.getString(long1)); } Helper.printMessage(new Date().getTime() - startD.getTime() + ""); if (set.containsAll(set3)) Helper.printMessage("The test passed."); else Helper.printMessage("The test failed."); } public static void main(String[] args) { testStrategy(new OurHashMapStorageStrategy(), 10000); } }

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Jonas

Level 41 , Vilnius, Lithuania

17 April 2020, 05:58

solution

I can't explain why are you getting NPE here, but what I did is: 1) use for-each loop to iterate through table ( for (FileBucket bucket : table) ) 2) check if bucket you took is not null, to avoid NPE ( if (bucket == null) return false; ) 3) check if that bucket has the right value ( if (bucket.getEntry().value.equals(value)) return true; ) 4) if for-each loop is not gonna return true, just return false after the loop, it means that the right value wasn't found. Good luck :)

yz Backend Developer

17 April 2020, 16:13

Thanks maan, it was really helpful... i was using == not equals and also my transfer method was incorrect thank u!