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Create java-hash-set examples #3

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142 changes: 142 additions & 0 deletions java-hash-set examples
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import java.util.HashSet;
import java.util.Set;

public class CreateHashSetExample {
public static void main(String[] args) {
// Creating a HashSet
Set<String> daysOfWeek = new HashSet<>();

// Adding new elements to the HashSet
daysOfWeek.add("Monday");
daysOfWeek.add("Tuesday");
daysOfWeek.add("Wednesday");
daysOfWeek.add("Thursday");
daysOfWeek.add("Friday");
daysOfWeek.add("Saturday");
daysOfWeek.add("Sunday");

// Adding duplicate elements will be ignored
daysOfWeek.add("Monday");

System.out.println(daysOfWeek);
}
}

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import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Set;

public class CreateHashSetFromCollectionExample {
public static void main(String[] args) {
List<Integer> numbersDivisibleBy5 = new ArrayList<>();
numbersDivisibleBy5.add(5);
numbersDivisibleBy5.add(10);
numbersDivisibleBy5.add(15);
numbersDivisibleBy5.add(20);
numbersDivisibleBy5.add(25);

List<Integer> numbersDivisibleBy3 = new ArrayList<>();
numbersDivisibleBy3.add(3);
numbersDivisibleBy3.add(6);
numbersDivisibleBy3.add(9);
numbersDivisibleBy3.add(12);
numbersDivisibleBy3.add(15);

// Creating a HashSet from another collection (ArrayList)
Set<Integer> numbersDivisibleBy5Or3 = new HashSet<>(numbersDivisibleBy5);

// Adding all the elements from an existing collection to a HashSet
numbersDivisibleBy5Or3.addAll(numbersDivisibleBy3);

System.out.println(numbersDivisibleBy5Or3);
}
}
***************************************************************************************************************************************************************************

import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Set;

public class HashSetRemoveExample {
public static void main(String[] args) {
Set<Integer> numbers = new HashSet<>();
numbers.add(2);
numbers.add(3);
numbers.add(4);
numbers.add(5);
numbers.add(6);
numbers.add(7);
numbers.add(8);
numbers.add(9);
numbers.add(10);

System.out.println("numbers : " + numbers);

// Remove an element from a HashSet (The remove() method returns false if the element does not exist in the HashSet)
boolean isRemoved = numbers.remove(10);
System.out.println("After remove(10) => " + numbers);

// Remove all elements belonging to a given collection from a HashSet
List<Integer> perfectSquares = new ArrayList<>();
perfectSquares.add(4);
perfectSquares.add(9);

numbers.removeAll(perfectSquares);
System.out.println("After removeAll(perfectSquares) => " + numbers);

// Remove all elements matching a given predicate
numbers.removeIf(num -> num % 2 == 0);
System.out.println("After removeIf() => " + numbers);

// Remove all elements from HashSet (clear it completely)
numbers.clear();
System.out.println("After clear() => " + numbers);
}
}

***************************************************************************************************************************************************************************

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

public class IterateOverHashSetExample {
public static void main(String[] args) {
Set<String> programmingLanguages = new HashSet<>();
programmingLanguages.add("C");
programmingLanguages.add("C++");
programmingLanguages.add("Java");
programmingLanguages.add("Python");
programmingLanguages.add("PHP");
programmingLanguages.add("Ruby");

System.out.println("=== Iterate over a HashSet using Java 8 forEach and lambda ===");
programmingLanguages.forEach(programmingLanguage -> {
System.out.println(programmingLanguage);
});

System.out.println("=== Iterate over a HashSet using iterator() ===");
Iterator<String> programmingLanguageIterator = programmingLanguages.iterator();
while (programmingLanguageIterator.hasNext()) {
String programmingLanguage = programmingLanguageIterator.next();
System.out.println(programmingLanguage);
}

System.out.println("=== Iterate over a HashSet using iterator() and Java 8 forEachRemaining() method ===");
programmingLanguageIterator = programmingLanguages.iterator();
programmingLanguageIterator.forEachRemaining(programmingLanguage -> {
System.out.println(programmingLanguage);
});

System.out.println("=== Iterate over a HashSet using simple for-each loop ===");
for(String programmingLanguage: programmingLanguages) {
System.out.println(programmingLanguage);
}
}
}


***************************************************************************************************************************************************************************