Added some new examples in LambdasAndStreams

.gitignore

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+# Default ignored files
+.idea
+target

LambdasAndStreams/.gitignore

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+# Default ignored files
+.idea
+target
+.class

LambdasAndStreams/pom.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+
+    <groupId>org.example</groupId>
+    <artifactId>Java8</artifactId>
+    <version>1.0-SNAPSHOT</version>
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <configuration>
+                    <source>16</source>
+                    <target>16</target>
+                </configuration>
+            </plugin>
+        </plugins>
+    </build>
+
+</project>

LambdasAndStreams/src/main/java/StreamsCodeDemoPart2.java

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+import java.util.*;
+import java.util.function.Function;
+import java.util.stream.Collectors;
+import java.util.stream.IntStream;
+import java.util.stream.Stream;
+
+/**
+ * Class to demonstrate Streams, record and generics in Java.
+ */
+public class StreamsCodeDemoPart2 {
+    // Enable this to see logs.
+    private static final boolean DEBUG = true;
+
+    public static void main(String[] args) {
+
+        // 1. Given a sentence, find and print the frequency of each word.
+        String sentence = "Java is a programming language. Java is versatile. Java is fun!";
+
+        Map<String, Long> wordFreqMap = Arrays.stream(sentence.split("\\s+"))
+                .collect(Collectors.groupingBy(String::toLowerCase, Collectors.counting()));
+
+        printArgs(wordFreqMap);
+
+        // 2. Given a list of integers, find out all the numbers starting with 1.
+
+        List<Integer> numList = Arrays.asList(12, 13, 18, 21, 90, 11);
+
+        List<Integer> numbersWithOne = numList.stream()
+                .filter(n -> String.valueOf(n).startsWith("1"))
+                .toList();
+
+        printArgs(numbersWithOne);
+
+        // 3. Given a list of names, group them by their first letter, and then count the number of names in each group.
+
+        String[] names = {"Alice", "Bob", "Charlie", "Amy", "Bill", "Anna", "John", "Michael", "Rambo", "Batman"};
+
+        Map<Character, Long> namesMap = Arrays.stream(names)
+                .collect(Collectors.groupingBy(s -> s.charAt(0), Collectors.counting()));
+
+        printArgs(namesMap);
+
+        // 4. Find and print duplicate numbers in an array if it contains multiple duplicates?
+
+        int[] arr = {2, 4, 2, 3, 1, 5, 5, 78, 3, 1, 5};
+
+        Arrays.stream(arr).boxed()
+                .collect(Collectors.groupingBy(e -> e, Collectors.counting()))
+                .entrySet().stream()
+                //key -value - 2 (k), 2(val)
+                .filter(entry -> entry.getValue() > 1)
+                .map(Map.Entry::getKey)
+                .forEach(StreamsCodeDemoPart2::printArgs);
+
+        // 5. How are duplicates removed from a given array in Java?
+
+        int[] newArr = Arrays.stream(arr).distinct().toArray();
+
+        printArgs(newArr);
+
+        // 6. Given a list of words, filter and print the palindromes
+
+        List<String> strings = List.of("level", "hello", "radar", "world", "deed");
+
+        List<String> palindromeWords = strings.stream().
+                filter(str -> str.contentEquals(new StringBuilder(str).reverse())).toList();
+
+        printArgs(palindromeWords);
+
+        // 7. How do you merge two sorted arrays into a single sorted array?
+        int[] array1 = {1, 3, 32, 5, 7};
+        int[] array2 = {2, 4, 6, 62, 8};
+
+        int[] sortedArray = IntStream.concat(Arrays.stream(array1), Arrays.stream(array2)).sorted().toArray();
+        printArgs(sortedArray);
+
+        // 8. Given two lists of strings, concatenate them and remove duplicates.
+
+        List<String> list1 = List.of("apple", "banana", "orange");
+        List<String> list2 = List.of("banana", "kiwi", "grape");
+
+        List<String> uniqueList = Stream
+                .concat(list1.stream(), list2.stream())
+                .distinct()
+                .toList();
+        printArgs(uniqueList);
+
+        // 9. Student Grade Classification - 70 and above pass
+
+        List<Student> students = List.of(
+                new Student("Alice", 85),
+                new Student("Bob", 60),
+                new Student("Charlie", 75),
+                new Student("David", 90)
+        );
+
+        Map<String, List<Student>> studentMap =
+                students.stream().collect(Collectors.groupingBy(student -> student.grade >= 70 ? "Pass" : "Fail"));
+
+        printArgs(studentMap);
+
+        // 10. Given a list of strings, sort them according to increasing order of their length.
+
+        List<String> fruits = Arrays.asList("Mango", "pear", "Apple", "Banana", "Pineapple", "Kiwi");
+
+        fruits.stream().sorted(Comparator.comparingInt(String::length)).forEach(StreamsCodeDemoPart2::printArgs);
+
+        // 11.Partition a list of numbers into two groups: even and odd, using a custom predicate.
+        List<Integer> numbers1 = Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10);
+        Map<Boolean, List<Integer>> partitionedNumbers = numbers1.stream()
+                .collect(Collectors.partitioningBy(n -> n % 2 == 0));
+
+        printArgs(partitionedNumbers);
+
+        // 12. Find the squares of the first three even numbers in a list.
+
+        List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10);
+        List<Integer> firstThreeSquares = numbers.stream()
+                .filter(n -> n % 2 == 0)
+                .map(n -> n * n)
+                .limit(3)
+                .toList();
+
+        printArgs(firstThreeSquares);
+
+        // 13. Flatten a list of lists
+
+        List<List<Integer>> listOfLists = Arrays.asList(Arrays.asList(1, 2), Arrays.asList(3, 4), Arrays.asList(5, 6));
+        List<Integer> flattenedList = listOfLists.stream()
+                .flatMap(List::stream)
+                .toList();
+
+        printArgs(flattenedList);
+
+        // 14. Find prime numbers in a given array.
+
+        int[] primeInputList = {2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 29, 30};
+
+        printArgs(
+                Arrays.stream(primeInputList)
+                        .filter(StreamsCodeDemoPart2::isPrime)
+                        .sorted()
+        );
+
+        // 15. String array to Map with String length as the key. Re-using fruits List here. :)
+
+        printArgs(
+                fruits.stream()
+                        .collect(
+                                Collectors.toMap(
+                                        Function.identity(),
+                                        String::length
+                                )
+                        )
+        );
+
+        // 16. Find the topper in the list of students. Re-using students here.
+        Optional<Student> topper = students.stream()
+                .max(Comparator.comparingInt(student -> student.grade));
+
+        topper.ifPresent(StreamsCodeDemoPart2::printArgs);
+    }
+
+    /**
+     * Helper method for printing the logs.
+     * This makes it easy to enable or disable logs.
+     *
+     * @param message Generic type to be printed. It could be a String, a List, or a Map.
+     */
+    private static <V> void printArgs(V message) {
+        if (DEBUG) {
+            System.out.println(message);
+        } else {
+            System.out.println("Please change 'DEBUG' to true to see logs.");
+        }
+    }
+
+    /**
+     * Method to check if the given number is prime or not.
+     *
+     * @param number int input for checking prime number.
+     * @return true if prime, false otherwise.
+     */
+    private static boolean isPrime(int number) {
+        if (number <= 1) {
+            return false;
+        }
+
+        for (int i = 2; i <= Math.sqrt(number); i++) {
+            if (number % i == 0)
+                return false;
+        }
+        return true;
+    }
+
+    /**
+     * Record to template a student's name and grade.
+     *
+     * @param name  String name of the student.
+     * @param grade int grade of the student.
+     */
+    private record Student(String name, int grade) {
+        @Override
+        public String toString() {
+            return "Student{" +
+                    "name='" + name + '\'' +
+                    ", grade=" + grade +
+                    '}';
+        }
+    }
+}