The core new features of Java 8 include Lambda expressions, Stream APIs, and default methods. 1. Lambda expressions simplify the implementation of functional interfaces, making the code more concise, but it should be noted that it is only applicable to functional interfaces and should not be too complicated; 2. The Stream API provides declarative data processing methods to improve collection operation efficiency, but should avoid using them on small amounts of data and reduce side effects; 3. The default method allows interfaces to define method implementations to enhance backward compatibility, but cannot access class state and need to resolve method conflict problems. The rational use of these features can improve code quality and development efficiency.
Java 8 is a major version update in the development of Java, bringing many practical and far-reaching new features. These new features not only improve the simplicity and readability of the code, but also significantly enhance Java's capabilities in functional programming.
Lambda expression: make the code simpler
Lambda expressions are one of the most eye-catching features of Java 8. It allows you to represent an instance of an interface with only one abstract method (i.e., a functional interface) in a more concise way. This is especially useful when dealing with collection traversals.
For example, before Java 8, you might need to start a thread with an anonymous inner class:
new Thread(new Runnable() {
@Override
public void run() {
System.out.println("Old way");
}
});Now you can do it with a line of Lambda expressions:
new Thread(() -> System.out.println("New way")).start();The following points should be paid attention to when using Lambda:
- Make sure the target interface is a functional interface (the @FunctionalInterface annotation can help check this).
- Lambda expressions are suitable for simple logic, but it is recommended to use conventional methods for overly complex logic.
- Don't abuse Lambda, especially in the case of multiple statements, it's more important to keep the code readable.
Stream API: Operating collections are more efficient
The Stream API provides a declarative way to process data collections, especially when combined with Lambda expressions, the code logic is clearer.
You can use Stream to filter, map and collect data. For example, find all even numbers from a list of integers and print them out:
List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5, 6);
numbers.stream()
.filter(n -> n % 2 == 0)
.forEach(System.out::println);There are several common misunderstandings to note when using Stream:
- Don't overuse Stream on small collections, performance advantages are usually reflected in large amounts of data.
- Avoid side effects in Stream operations (such as modifying external variables), which can easily cause concurrent problems or difficult to debug errors.
- Learn more about the differences between intermediate operations (such as filter, map) and terminal operations (such as forEach, collect).
Default method: The interface can also be implemented
Java 8 allows the definition of default methods in an interface, which means you can add new methods to the interface without breaking existing implementations. This feature is mainly intended to support backward compatibility.
For example, you can define an interface with a default method like this:
public interface MyInterface {
default void doSomething() {
System.out.println("Doing something");
}
} Then any class that implements the interface will automatically have this method and no additional implementation is required.
Although this function is powerful, there are some things to note:
- The default method cannot access the state of the implementation class because it does not have this pointer to a concrete object.
- If the two interfaces have default methods with the same name, the implementation class must specify which one to use, otherwise the compilation will fail.
- Try to avoid using the default method heavily in the interface unless it is indeed for compatibility considerations.
Basically that's it. These new features of Java 8 have changed the way we write code, especially the combination of Lambda and Stream, making many of the originally verbose operations elegant and concise. However, they are not omnipotent, and only when used reasonably can they achieve their maximum value.
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