3 Powerful Java Stream Operations Worth Mastering

Transform Your Collection Processing with These 3 Powerful Stream Operations

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Stream operation in Java are powerful tools that can help you write more concise and readable code. In this article I will explore three essential operation that can help reach more readable code.

Before start using Stream API let’s start with a sample data class.

public record Person(
  String name,
  int age,
  String department,
  double salary) {}

List<Person> employees = Arrays.asList(
    new Person("John", 30, "Engineering", 75000.0),
    new Person("Alice", 25, "Engineering", 65000.0),
    new Person("Bob", 35, "HR", 55000.0),
    new Person("Carol", 28, "Engineering", 70000.0),
    new Person("David", 40, "HR", 85000.0)
);

groupingBy

This collector is incredibly useful when you need to group elements by a specific attribute. In example below, the code grouped employees by their department. This way can be used for creating categorized data structures.

Map<String, List<Person>> byDepartment = employees.stream()
    .collect(Collectors.groupingBy(Person::department));

groupingBy and averagingDouble