Lernen Lambdas in Stream API | Advanced Lambda Usage

You will often encounter the Stream API when processing collections of data in Java. The Stream API allows you to perform complex data operations in a concise and readable way. Lambda expressions play a central role in this, as they are used to define the behavior of stream operations such as map, filter, and reduce. These operations enable you to transform, filter, and aggregate data declaratively, rather than writing explicit loops and conditionals.

Main.java


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package com.example;

import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;

public class Main {
    public static void main(String[] args) {
        List<String> names = Arrays.asList("Alice", "Bob", "Charlie", "David", "Eve");
        List<String> upperCaseNamesWithE = names.stream()
            .filter(name -> name.contains("e"))
            .map(name -> name.toUpperCase())
            .collect(Collectors.toList());
        System.out.println(upperCaseNamesWithE);
    }
}

Using lambdas within streams allows you to focus on what you want to do with the data, rather than how to do it. This declarative style improves code readability and maintainability. You express operations like filtering, mapping, and reducing as a sequence of transformations, making your intent clear and your code less error-prone.

Main.java


              123456789101112131415
            
package com.example;

import java.util.Arrays;
import java.util.List;
import java.util.Optional;

public class Main {
    public static void main(String[] args) {
        List<Integer> numbers = Arrays.asList(10, 23, 5, 99, 34);
        Optional<Integer> max = numbers.stream()
            .max((a, b) -> a.compareTo(b));
        max.ifPresent(m -> System.out.println("Max value: " + m));
    }
}

1. Which of the following Stream API methods commonly use lambda expressions?

2. What is the main difference between the `map` and `filter` methods in a Java stream?

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Abschnitt 2. Kapitel 5

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Main.java


              1234567891011121314151617
            
package com.example;

import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;

public class Main {
    public static void main(String[] args) {
        List<String> names = Arrays.asList("Alice", "Bob", "Charlie", "David", "Eve");
        List<String> upperCaseNamesWithE = names.stream()
            .filter(name -> name.contains("e"))
            .map(name -> name.toUpperCase())
            .collect(Collectors.toList());
        System.out.println(upperCaseNamesWithE);
    }
}

Main.java


              123456789101112131415
            
package com.example;

import java.util.Arrays;
import java.util.List;
import java.util.Optional;

public class Main {
    public static void main(String[] args) {
        List<Integer> numbers = Arrays.asList(10, 23, 5, 99, 34);
        Optional<Integer> max = numbers.stream()
            .max((a, b) -> a.compareTo(b));
        max.ifPresent(m -> System.out.println("Max value: " + m));
    }
}

1. Which of the following Stream API methods commonly use lambda expressions?

2. What is the main difference between the `map` and `filter` methods in a Java stream?

War alles klar?

Danke für Ihr Feedback!

Abschnitt 2. Kapitel 5

Lambdas in Stream API

1. Which of the following Stream API methods commonly use lambda expressions?

2. What is the main difference between the map and filter methods in a Java stream?

Lambdas in Stream API

1. Which of the following Stream API methods commonly use lambda expressions?

2. What is the main difference between the map and filter methods in a Java stream?

2. What is the main difference between the `map` and `filter` methods in a Java stream?

2. What is the main difference between the `map` and `filter` methods in a Java stream?