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Rajeev Kumar Singh
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LinkedList and LinkedHashMap
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‎Readme.md

+8-4
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@@ -2,10 +2,14 @@
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1. [Java ArrayList Tutorial with Examples](https://www.callicoder.com/java-arraylist/)
44

5-
2. [Java HashMap Tutorial with Examples](https://www.callicoder.com/java-hashmap/)
5+
2. [Java LinkedList Tutorial with Examples](https://www.callicoder.com/java-linkedlist/)
66

7-
3. [Java HashSet Tutorial with Examples](https://www.callicoder.com/java-hashset/)
7+
3. [Java HashMap Tutorial with Examples](https://www.callicoder.com/java-hashmap/)
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9-
4. [Java TreeMap Tutorial with Examples](https://www.callicoder.com/java-treemap/)
9+
4. [Java LinkedHashMap Tutorial with Examples](https://www.callicoder.com/java-linkedhashmap/)
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11-
5. [Java TreeSet Tutorial with Examples](https://www.callicoder.com/java-treeset/)
11+
5. [Java TreeMap Tutorial with Examples](https://www.callicoder.com/java-treemap/)
12+
13+
6. [Java HashSet Tutorial with Examples](https://www.callicoder.com/java-hashset/)
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15+
7. [Java TreeSet Tutorial with Examples](https://www.callicoder.com/java-treeset/)

‎java-arraylist-examples/src/ArrayListSortExample.java

+1-1
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@@ -20,7 +20,7 @@ public int compare(String name1, String name2) {
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}
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});
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23-
// The above `sort()` method call can also be written simply using lambda expressions
23+
// The above `sort()` method call can also be written simply using lambda expression
2424
names.sort((name1, name2) -> name1.compareTo(name2));
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2626
// Following is an even more concise solution

‎java-arraylist-examples/src/RemoveElementsFromArrayListExample.java

+3-2
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@@ -19,11 +19,12 @@ public static void main(String[] args) {
1919
programmingLanguages.remove(5);
2020
System.out.println("After remove(5): " + programmingLanguages);
2121

22-
// Remove the element "Kotlin" (The remove() method returns false if the element does not exist in the ArrayList)
22+
// Remove the first occurrence of the given element from the ArrayList
23+
// (The remove() method returns false if the element does not exist in the ArrayList)
2324
boolean isRemoved = programmingLanguages.remove("Kotlin");
2425
System.out.println("After remove(\"Kotlin\"): " + programmingLanguages);
2526

26-
// Remove all the elements belonging to the collection scriptingLanguages
27+
// Remove all the elements that exist in a given collection
2728
List<String> scriptingLanguages = new ArrayList<>();
2829
scriptingLanguages.add("Python");
2930
scriptingLanguages.add("Ruby");

‎java-arraylist-examples/src/SearchElementsInArrayListExample.java

+1-1
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@@ -15,7 +15,7 @@ public static void main(String[] args) {
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// Check if an ArrayList contains a given element
1616
System.out.println("Does names array contain \"Bob\"? : " + names.contains("Bob"));
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18-
// Find the index of first occurrence of an element in an ArrayList
18+
// Find the index of the first occurrence of an element in an ArrayList
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System.out.println("indexOf \"Steve\": " + names.indexOf("Steve"));
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System.out.println("indexOf \"Mark\": " + names.indexOf("Mark"));
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‎java-arraylist-examples/src/SynchronizedArrayListExample.java

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@@ -15,7 +15,7 @@ public static void main(String[] args) throws InterruptedException {
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// Create a thread pool of size 10
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ExecutorService executorService = Executors.newFixedThreadPool(10);
1717

18-
// Create a Runnable task that increments the each element of the ArrayList by one
18+
// Create a Runnable task that increments each element of the ArrayList by one
1919
Runnable task = () -> {
2020
incrementArrayList(safeArrayList);
2121
};

‎java-arraylist-examples/src/UnsafeArrayListExample.java

+1-1
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@@ -14,7 +14,7 @@ public static void main(String[] args) throws InterruptedException {
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// Create a thread pool of size 10
1515
ExecutorService executorService = Executors.newFixedThreadPool(10);
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17-
// Create a Runnable task that increments the each element of the ArrayList by one
17+
// Create a Runnable task that increments each element of the ArrayList by one
1818
Runnable task = () -> {
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incrementArrayList(unsafeArrayList);
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};

‎java-hashmap-examples/src/AccessKeysFromHashMapExample.java

+12-2
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@@ -5,13 +5,15 @@ public class AccessKeysFromHashMapExample {
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public static void main(String[] args) {
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Map<String, String> userCityMapping = new HashMap<>();
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8-
// Check if HashMap is empty
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// Check if a HashMap is empty
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System.out.println("is userCityMapping empty? : " + userCityMapping.isEmpty());
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1111
userCityMapping.put("John", "New York");
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userCityMapping.put("Rajeev", "Bengaluru");
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userCityMapping.put("Steve", "London");
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15+
System.out.println("userCityMapping HashMap : " + userCityMapping);
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// Find the size of a HashMap
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System.out.println("We have the city information of " + userCityMapping.size() + " users");
1719

@@ -25,9 +27,17 @@ public static void main(String[] args) {
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System.out.println("City details not found for user " + userName);
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}
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30+
// Check if a value exists in a HashMap
31+
if(userCityMapping.containsValue("New York")) {
32+
System.out.println("There is a user in the userCityMapping who lives in New York");
33+
} else {
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System.out.println("There is not user in the userCityMapping who lives in New York");
35+
}
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// Modify the value assigned to an existing key
2939
userCityMapping.put(userName, "California");
30-
System.out.println(userName + " moved to a new city " + userCityMapping.get(userName));
40+
System.out.println(userName + " moved to a new city " + userCityMapping.get(userName) + ", New userCityMapping : " + userCityMapping);
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3242
// The get() method returns `null` if the specified key was not found in the HashMap
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System.out.println("Lisa's city : " + userCityMapping.get("Lisa"));

‎java-hashmap-examples/src/CreateHashMapExample.java

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@@ -11,6 +11,9 @@ public static void main(String[] args) {
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numberMapping.put("Two", 2);
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numberMapping.put("Three", 3);
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14+
// Add a new key-value pair only if the key does not exist in the HashMap, or is mapped to `null`
15+
numberMapping.putIfAbsent("Four", 4);
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1417
System.out.println(numberMapping);
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}
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}

‎java-hashmap-examples/src/HashMapEntryKeySetValuesExample.java

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@@ -15,14 +15,14 @@ public static void main(String[] args) {
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1616
// HashMap's entry set
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Set<Map.Entry<String, String>> countryISOCodeEntries = countryISOCodeMapping.entrySet();
18-
System.out.println(countryISOCodeEntries);
18+
System.out.println("countryISOCode entries : " + countryISOCodeEntries);
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2020
// HashMap's key set
2121
Set<String> countries = countryISOCodeMapping.keySet();
22-
System.out.println("Countries : " + countries);
22+
System.out.println("countries : " + countries);
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2424
// HashMap's values
2525
Collection<String> isoCodes = countryISOCodeMapping.values();
26-
System.out.println("ISO Codes : " + isoCodes);
26+
System.out.println("isoCodes : " + isoCodes);
2727
}
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}

‎java-hashmap-examples/src/RemoveKeysFromHashMapExample.java

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@@ -10,16 +10,18 @@ public static void main(String[] args) {
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System.out.println("Husband-Wife Mapping : " + husbandWifeMapping);
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13-
// Unfortunately, Chris got divorced. Let's remove him from the mapping
13+
// Remove a key from the HashMap
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// Ex - Unfortunately, Chris got divorced. Let's remove him from the mapping
1415
String husband = "Chris";
1516
String wife = husbandWifeMapping.remove(husband);
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1718
System.out.println("Couple (" + husband + " => " + wife + ") got divorced");
1819
System.out.println("New Mapping : " + husbandWifeMapping);
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20-
// Divorce "Jack" only if He is married to "Linda"
21+
// Remove a key from the HashMap only if it is mapped to the given value
22+
// Ex - Divorce "Jack" only if He is married to "Linda"
2123
boolean isRemoved = husbandWifeMapping.remove("Jack", "Linda");
22-
System.out.println("Did Jack got removed from the mapping? : " + isRemoved);
24+
System.out.println("Did Jack get removed from the mapping? : " + isRemoved);
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2426
// remove() returns null if the mapping was not found for the supplied key
2527
wife = husbandWifeMapping.remove("David");

‎java-linkedhashmap-examples/src/AccessEntriesFromLinkedHashMapExample.java

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1+
import java.util.LinkedHashMap;
2+
3+
public class AccessEntriesFromLinkedHashMapExample {
4+
public static void main(String[] args) {
5+
LinkedHashMap<Integer, String> customerIdNameMapping = new LinkedHashMap<>();
6+
7+
customerIdNameMapping.put(1001, "Jack");
8+
customerIdNameMapping.put(1002, "David");
9+
customerIdNameMapping.put(1003, "Steve");
10+
customerIdNameMapping.put(1004, "Alice");
11+
customerIdNameMapping.put(1005, "Marie");
12+
13+
System.out.println("customerIdNameMapping : " + customerIdNameMapping);
14+
15+
// Check if a key exists in the LinkedHashMap
16+
Integer id = 1005;
17+
if(customerIdNameMapping.containsKey(id)) {
18+
System.out.println("Found the customer with id " + id + " : " + customerIdNameMapping.get(id));
19+
} else {
20+
System.out.println("Customer with id " + id + " does not exist");
21+
}
22+
23+
// Check if a value exists in the LinkedHashMap
24+
String name = "David";
25+
if(customerIdNameMapping.containsValue(name)) {
26+
System.out.println("A customer named " + name + " exist in the map");
27+
} else {
28+
System.out.println("No customer found with name " + name + " in the map");
29+
}
30+
31+
// Change the value associated with an existing key
32+
id = 1004;
33+
customerIdNameMapping.put(id, "Bob");
34+
System.out.println("Changed the name of customer with id " + id + ", New mapping : " + customerIdNameMapping);
35+
}
36+
}

‎java-linkedhashmap-examples/src/CreateLinkedHashMapExample.java

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1+
import java.util.LinkedHashMap;
2+
3+
public class CreateLinkedHashMapExample {
4+
public static void main(String[] args) {
5+
// Creating a LinkedHashMap
6+
LinkedHashMap<String, Integer> wordNumberMapping = new LinkedHashMap<>();
7+
8+
// Adding new key-value pairs to the LinkedHashMap
9+
wordNumberMapping.put("one", 1);
10+
wordNumberMapping.put("two", 2);
11+
wordNumberMapping.put("three", 3);
12+
wordNumberMapping.put("four", 4);
13+
14+
// Add a new key-value pair only if the key does not exist in the LinkedHashMap, or is mapped to `null`
15+
wordNumberMapping.putIfAbsent("five", 5);
16+
17+
18+
System.out.println(wordNumberMapping);
19+
}
20+
}

‎java-linkedhashmap-examples/src/IterateOverLinkedHashMapExample.java

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1+
import java.util.Iterator;
2+
import java.util.LinkedHashMap;
3+
import java.util.Map;
4+
5+
public class IterateOverLinkedHashMapExample {
6+
public static void main(String[] args) {
7+
LinkedHashMap<String, String> userCityMapping = new LinkedHashMap<>();
8+
9+
userCityMapping.put("Rajeev", "Bengaluru");
10+
userCityMapping.put("Chris", "London");
11+
userCityMapping.put("David", "Paris");
12+
userCityMapping.put("Jesse", "California");
13+
14+
System.out.println("=== Iterating over a LinkedHashMap using Java 8 forEach loop ===");
15+
userCityMapping.forEach((user, city) -> {
16+
System.out.println(user + " => " + city);
17+
});
18+
19+
20+
System.out.println("\n=== Iterating over the LinkedHashMap's entrySet using Java 8 forEach loop ===");
21+
userCityMapping.entrySet().forEach(entry -> {
22+
System.out.println(entry.getKey() + " => " + entry.getValue());
23+
});
24+
25+
System.out.println("\n=== Iterating over the entrySet of a LinkedHashMap using iterator() ===");
26+
Iterator<Map.Entry<String, String>> userCityMappingIterator = userCityMapping.entrySet().iterator();
27+
while (userCityMappingIterator.hasNext()) {
28+
Map.Entry<String, String> entry = userCityMappingIterator.next();
29+
System.out.println(entry.getKey() + " => " + entry.getValue());
30+
}
31+
32+
System.out.println("\n=== Iterating over the entrySet of a LinkedHashMap using iterator() and forEachRemaining ===");
33+
userCityMappingIterator = userCityMapping.entrySet().iterator();
34+
userCityMappingIterator.forEachRemaining(entry -> {
35+
System.out.println(entry.getKey() + " => " + entry.getValue());
36+
});
37+
}
38+
}

‎java-linkedhashmap-examples/src/RemoveEntriesFromLinkedHashMapExample.java

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1+
import java.util.LinkedHashMap;
2+
3+
public class RemoveEntriesFromLinkedHashMapExample {
4+
public static void main(String[] args) {
5+
LinkedHashMap<String, String> husbandWifeMapping = new LinkedHashMap<>();
6+
7+
husbandWifeMapping.put("Rajeev", "Jennifer");
8+
husbandWifeMapping.put("John", "Maria");
9+
husbandWifeMapping.put("Chris", "Lisa");
10+
husbandWifeMapping.put("Steve", "Susan");
11+
12+
System.out.println("husbandWifeMapping : " + husbandWifeMapping);
13+
14+
// Remove the entry with the given key from the LinkedHashMap
15+
String wife = husbandWifeMapping.remove("John");
16+
System.out.println("Removed John and his wife " + wife + " from the mapping. New husbandWifeMapping : " + husbandWifeMapping);
17+
18+
// Remove the entry with the given key from the LinkedHashMap only if the key is mapped to the given value
19+
boolean isRemoved = husbandWifeMapping.remove("John", "Susan");
20+
System.out.println("Did John get removed from the mapping? : " + isRemoved);
21+
}
22+
}

‎java-linkedlist-examples/src/CreateLinkedListExample.java

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1+
import java.util.ArrayList;
2+
import java.util.LinkedList;
3+
import java.util.List;
4+
5+
public class CreateLinkedListExample {
6+
public static void main(String[] args) {
7+
// Creating a LinkedList
8+
LinkedList<String> friends = new LinkedList<>();
9+
10+
// Adding new elements to the end of the LinkedList using add() method.
11+
friends.add("Rajeev");
12+
friends.add("John");
13+
friends.add("David");
14+
friends.add("Chris");
15+
16+
System.out.println("Initial LinkedList : " + friends);
17+
18+
// Adding an element at the specified position in the LinkedList
19+
friends.add(3, "Lisa");
20+
System.out.println("After add(3, \"Lisa\") : " + friends);
21+
22+
// Adding an element at the beginning of the LinkedList
23+
friends.addFirst("Steve");
24+
System.out.println("After addFirst(\"Steve\") : " + friends);
25+
26+
// Adding an element at the end of the LinkedList (This method is equivalent to the add() method)
27+
friends.addLast("Jennifer");
28+
System.out.println("After addLast(\"Jennifer\") : " + friends);
29+
30+
// Adding all the elements from an existing collection to the end of the LinkedList
31+
List<String> familyFriends = new ArrayList<>();
32+
familyFriends.add("Jesse");
33+
familyFriends.add("Walt");
34+
35+
friends.addAll(familyFriends);
36+
System.out.println("After addAll(familyFriends) : " + friends);
37+
}
38+
}

‎java-linkedlist-examples/src/IterateOverLinkedListExample.java

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1+
import java.util.Iterator;
2+
import java.util.LinkedList;
3+
import java.util.ListIterator;
4+
5+
public class IterateOverLinkedListExample {
6+
public static void main(String[] args) {
7+
LinkedList<String> humanSpecies = new LinkedList<>();
8+
9+
humanSpecies.add("Homo Sapiens");
10+
humanSpecies.add("Homo Neanderthalensis");
11+
humanSpecies.add("Homo Erectus");
12+
humanSpecies.add("Home Habilis");
13+
14+
System.out.println("=== Iterate over a LinkedList using Java 8 forEach loop ===");
15+
humanSpecies.forEach(name -> {
16+
System.out.println(name);
17+
});
18+
19+
20+
System.out.println("\n=== Iterate over a LinkedList using iterator() ===");
21+
Iterator<String> humanSpeciesIterator = humanSpecies.iterator();
22+
while (humanSpeciesIterator.hasNext()) {
23+
String speciesName = humanSpeciesIterator.next();
24+
System.out.println(speciesName);
25+
}
26+
27+
System.out.println("\n=== Iterate over a LinkedList using iterator() and Java 8 forEachRemaining() method ===");
28+
humanSpeciesIterator = humanSpecies.iterator();
29+
humanSpeciesIterator.forEachRemaining(speciesName -> {
30+
System.out.println(speciesName);
31+
});
32+
33+
System.out.println("\n=== Iterate over a LinkedList using descendingIterator() ===");
34+
Iterator<String> descendingHumanSpeciesIterator = humanSpecies.descendingIterator();
35+
while (descendingHumanSpeciesIterator.hasNext()) {
36+
String speciesName = descendingHumanSpeciesIterator.next();
37+
System.out.println(speciesName);
38+
}
39+
40+
41+
System.out.println("\n=== Iterate over a LinkedList using listIterator() ===");
42+
// ListIterator can be used to iterate over the LinkedList in both forward and backward directions
43+
// In this example, we start from the end of the list and traverse backwards
44+
ListIterator<String> humanSpeciesListIterator = humanSpecies.listIterator(humanSpecies.size());
45+
while (humanSpeciesListIterator.hasPrevious()) {
46+
String speciesName = humanSpeciesListIterator.previous();
47+
System.out.println(speciesName);
48+
}
49+
50+
System.out.println("\n=== Iterate over a LinkedList using simple for-each loop ===");
51+
for(String speciesName: humanSpecies) {
52+
System.out.println(speciesName);
53+
}
54+
}
55+
}

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