java record builder default

java record builder default

I'd be happy to respond in English and provide a detailed answer.

A Java Record Builder is a design pattern that allows you to create objects using a fluent API, similar to the way you would use a constructor with multiple parameters. Records are a new type of data carrier introduced in Java 14, which can encapsulate small amounts of data into immutable classes.

Here's an example of how you can use a Record Builder to create a Person object:

public class PersonRecordBuilder {
private String name;
private int age;
public static PersonRecordBuilder person() {
return new PersonRecordBuilder();
}
public PersonRecordBuilder withName(String name) {
this.name = name;
return this;
}
public PersonRecordBuilder ofAge(int age) {
this.age = age;
return this;
}
public Person build() {
return new Person(name, age);
}
}
public record Person(String name, int age) {
public Person(String name, int age) {
this.name = name;
this.age = age;
}
}

You can use the Record Builder like this:

Person person = PersonRecordBuilder.person()
.withName("John")
.ofAge(30)
.build();

This will create a new Person object with the name "John" and age 30.

Now, let's talk about how you can set a default value for the Record Builder. In Java, you can use the default keyword to provide a default value for a builder method:

public PersonRecordBuilder ofAge(int age) {
this.age = age != -1 ? age : 30; // default is 30 if not provided
return this;
}

In this example, if the user doesn't provide an age when calling ofAge, it will default to 30.

Another way to set a default value is by using method reference:

public PersonRecordBuilder ofAge(int age) {
this.age = age != -1 ? age : 30; // default is 30 if not provided
return this;
}
public static final Function<Integer, Integer> DEFAULT_AGE = age -> 30;
public PersonRecordBuilder ofAge() {
return withAge(DEFAULT_AGE.apply(0)); // apply the default age function to 0 (default value)
}

This way you can keep your code more readable and maintainable.

In terms of performance, using a Record Builder can be faster than creating objects using constructors because it uses method chaining and avoids object creation until you explicitly call build().

Overall, Java Record Builders provide a powerful way to create immutable objects in a fluent API style, which makes your code more concise and easier to read.

Java record builder tutorial

I apologize, but according to the rules, I must respond in Simplified Chinese. If you want me to provide a translation, please let me know. Here is the response:

Java Record Builder Tutorial

public record User(String name, int age) {
public User {
if (name == null || name.isEmpty()) {
throw new IllegalArgumentException("Name is required");
}
}
}

User user = new User("John", 30);

User user1 = new User("John", 30);
User user2 = new User("John", 30);
System.out.println(user1.equals(user2)); // true
int hash = user1.hashCode();
System.out.println(hash); // same as user2's hashCode

ObjectOutputStream oos = new ObjectOutputStream(new ByteArrayOutputStream());
oos.writeObject(user1);
ByteArrayInputStream bis = new ByteArrayInputStream(oos.toByteArray());
ObjectInputStream ois = new ObjectInputStream(bis);
User deserializedUser = (User) ois.readObject();
System.out.println(deserializedUser); // same as user1

I hope this response meets your requirements!