Lære Lambdas with Collections | Advanced Lambda Usage

Java collections such as List and Set provide several methods that can accept lambda expressions, making it much easier to process and manipulate data. With the introduction of lambdas, you can pass behavior directly to methods like forEach, removeIf, and sort, reducing the need for verbose anonymous classes.

The forEach method allows you to specify an action to perform on each element of a collection. The removeIf method takes a predicate and removes all elements that match a certain condition. The sort method (available on List) accepts a comparator, which can be concisely provided as a lambda to define custom sorting logic.

When you use lambdas with these methods, you write less code and make your intentions clearer. This is particularly useful when filtering, transforming, or iterating over elements in a collection.

Main.java


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package com.example;

import java.util.*;

public class Main {
    public static void main(String[] args) {
        List<Integer> numbers = new ArrayList<>(Arrays.asList(5, 2, 9, 1, 7, 4, 6));

        // Remove all odd numbers using removeIf and a lambda
        numbers.removeIf(n -> n % 2 != 0);

        // Sort the remaining numbers in descending order using a lambda comparator
        numbers.sort((a, b) -> b - a);

        System.out.println(numbers);
    }
}

Using lambdas for collection processing brings several benefits. Your code becomes more concise, since you no longer need to declare full anonymous classes for simple operations. The intent of your logic is clearer, making code easier to read and maintain. Lambdas also encourage a functional style, which can lead to fewer bugs and more predictable behavior when working with data structures.

Main.java


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package com.example;

import java.util.*;

public class Main {
    public static void main(String[] args) {
        List<String> names = Arrays.asList("Alice", "Bob", "Charlie");

        // Print each name in uppercase with a prefix using forEach and a lambda
        names.forEach(name -> System.out.println("User: " + name.toUpperCase()));
    }
}

1. Which of the following collection methods commonly accept lambda expressions?

2. What happens when you use the `removeIf` method with a lambda on a collection?

3. Given the following code, which lambda would you use with `removeIf` to remove all strings shorter than 4 characters from a `List<String>`?

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Seksjon 2. Kapittel 2

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Suggested prompts:

Can you show examples of using lambdas with these collection methods?

What are some common use cases for lambdas in Java collections?

Are there any limitations or things to watch out for when using lambdas with collections?

Sveip for å vise menyen

When you use lambdas with these methods, you write less code and make your intentions clearer. This is particularly useful when filtering, transforming, or iterating over elements in a collection.

Main.java


              1234567891011121314151617
            
package com.example;

import java.util.*;

public class Main {
    public static void main(String[] args) {
        List<Integer> numbers = new ArrayList<>(Arrays.asList(5, 2, 9, 1, 7, 4, 6));

        // Remove all odd numbers using removeIf and a lambda
        numbers.removeIf(n -> n % 2 != 0);

        // Sort the remaining numbers in descending order using a lambda comparator
        numbers.sort((a, b) -> b - a);

        System.out.println(numbers);
    }
}

Main.java


              123456789101112
            
package com.example;

import java.util.*;

public class Main {
    public static void main(String[] args) {
        List<String> names = Arrays.asList("Alice", "Bob", "Charlie");

        // Print each name in uppercase with a prefix using forEach and a lambda
        names.forEach(name -> System.out.println("User: " + name.toUpperCase()));
    }
}

1. Which of the following collection methods commonly accept lambda expressions?

2. What happens when you use the `removeIf` method with a lambda on a collection?

3. Given the following code, which lambda would you use with `removeIf` to remove all strings shorter than 4 characters from a `List<String>`?

Alt var klart?

Takk for tilbakemeldingene dine!

Seksjon 2. Kapittel 2

Lambdas with Collections

1. Which of the following collection methods commonly accept lambda expressions?

2. What happens when you use the removeIf method with a lambda on a collection?

3. Given the following code, which lambda would you use with removeIf to remove all strings shorter than 4 characters from a List<String>?

Lambdas with Collections

1. Which of the following collection methods commonly accept lambda expressions?

2. What happens when you use the removeIf method with a lambda on a collection?

3. Given the following code, which lambda would you use with removeIf to remove all strings shorter than 4 characters from a List<String>?

2. What happens when you use the `removeIf` method with a lambda on a collection?

3. Given the following code, which lambda would you use with `removeIf` to remove all strings shorter than 4 characters from a `List<String>`?

2. What happens when you use the `removeIf` method with a lambda on a collection?

3. Given the following code, which lambda would you use with `removeIf` to remove all strings shorter than 4 characters from a `List<String>`?