Lecture 83:-  Java Stream Examples

Here are some Java stream examples that demonstrate various stream operations:

1. Filtering and Collecting:

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   import java.util.Arrays; import java.util.List; import java.util.stream.Collectors; public class StreamFilterExample {    public static void main(String[] args) {        List<String> fruits = Arrays.asList("apple", "banana", "cherry", "orange", "grape");        // Filter fruits that start with 'a' and collect them into a new list        List<String> filteredFruits = fruits.stream()            .filter(fruit -> fruit.startsWith("a"))            .collect(Collectors.toList());        System.out.println(filteredFruits); // Output: [apple]    } }

2. Mapping:

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   import java.util.Arrays; import java.util.List; import java.util.stream.Collectors; public class StreamMapExample {    public static void main(String[] args) {        List<String> names = Arrays.asList("Alice", "Bob", "Charlie");        // Map names to their lengths and collect the lengths into a new list        List<Integer> nameLengths = names.stream()            .map(name -> name.length())            .collect(Collectors.toList());        System.out.println(nameLengths); // Output: [5, 3, 7]    } }

3. Sorting:

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   import java.util.Arrays; import java.util.List; import java.util.stream.Collectors; public class StreamSortExample {    public static void main(String[] args) {        List<String> fruits = Arrays.asList("apple", "banana", "cherry", "orange", "grape");        // Sort fruits in alphabetical order and collect them into a new list        List<String> sortedFruits = fruits.stream()            .sorted()            .collect(Collectors.toList());        System.out.println(sortedFruits); // Output: [apple, banana, cherry, grape, orange]    } }

4. Aggregation:

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   import java.util.Arrays; import java.util.List; public class StreamAggregationExample {    public static void main(String[] args) {        List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5);        // Calculate the sum of all numbers        int sum = numbers.stream()            .reduce(0, (a, b) -> a + b);        System.out.println("Sum: " + sum); // Output: Sum: 15    } }

5. Distinct Elements:

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   import java.util.Arrays; import java.util.List; import java.util.stream.Collectors; public class StreamDistinctExample {    public static void main(String[] args) {        List<String> colors = Arrays.asList("red", "blue", "green", "red", "yellow");        // Find distinct colors and collect them into a new list        List<String> distinctColors = colors.stream()            .distinct()            .collect(Collectors.toList());        System.out.println(distinctColors); // Output: [red, blue, green, yellow]    } }

6. Counting:

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   import java.util.Arrays; import java.util.List; public class StreamCountExample {    public static void main(String[] args) {        List<String> fruits = Arrays.asList("apple", "banana", "cherry", "orange", "grape");        // Count the number of fruits in the list        long count = fruits.stream()            .count();        System.out.println("Count: " + count); // Output: Count: 5    } }

These examples showcase some common operations that can be performed using Java streams. The stream API provides a powerful and expressive way to manipulate data in a functional and declarative style. It is particularly useful for processing large datasets and simplifying complex data manipulation tasks.