Java Stream Examples

Lecture 83:-  Java Stream Examples

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

1. Filtering and Collecting:

   javaCopy code
   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:

   javaCopy code
   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:

   javaCopy code
   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:

   javaCopy code
   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:

   javaCopy code
   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:

   javaCopy code
   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.

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