The builder pattern is a creative design pattern in Java. Its main purpose is to decompose the construction process of a complex object into a construction process of multiple simple objects, and to assemble these construction processes in a certain order, ultimately realizing the creation of complex objects. This article will introduce the builder model in Java in detail, including its definition, structure, implementation method, and application scenarios.
Preface
When we need to create an object with multiple properties or components, we usually need to use a large number of constructors and setter methods. As properties or components increase, this approach can easily become confusing and difficult to maintain. At this point, the Builder Mode can solve this problem well.
The builder pattern breaks down the object construction process into multiple steps. The caller selects the required steps according to needs and assembles them in a certain order, ultimately realizing the creation of complex objects. By using the builder pattern, the object's construction process and specific build implementations can be separated, thereby improving the maintainability and readability of the code.
definition
The builder pattern is a creation pattern defined as follows:
Separate the construction process of a complex object from its representation, so that the same construction process can create different representations.
In other words, the builder pattern breaks down the construction process of an object into a construction process of multiple simple objects and assembles it in a certain order, thereby realizing the creation of complex objects. By using the builder pattern, the object construction process and specific construction implementation can be independent of each other, thereby improving the maintainability and readability of the code.
structure
Builder mode contains the following characters:
1. Product category
A product class is a complex object with multiple attributes or components, which consists of multiple simple objects.
public class Product {
private String part1;
private String part2;
private String part3;
// Omit the getter and setter methods}2. Abstract Builder
The builder class is an abstract class or interface that defines abstract methods for creating parts of a product object. In practical applications, it is usually necessary to define multiple different builder classes to create different types of product objects.
public interface Builder {
void buildPart1();
void buildPart2();
void buildPart3();
Product getResult();
}3. Concrete Builder
The concrete builder class is a subclass of the abstract builder class, which implements all abstract methods defined in the abstract builder class and assembles various parts of the product object according to specific needs.
public class ConcreteBuilder implements Builder {
private Product product = new Product();
@Override
public void buildPart1() {
product.setPart1("part1");
}
@Override
public void buildPart2() {
product.setPart2("part2");
}
@Override
public void buildPart3() {
product.setPart3("part3");
}
@Override
public Product getResult() {
return product;
}
}4. Director class (Director)
The instructor class is responsible for creating instances of the specific builder class and calling methods in the specific builder class to assemble parts of the product object. In practical applications, only one instructor class is usually needed.
public class Director {
public void construct(Builder builder) {
builder.buildPart1();
builder.buildPart2();
builder.buildPart3();
}
}The above is the structure of the builder model. Let us explain in detail its implementation method below.
Implementation method
When actually using Builder mode, you usually need to follow these steps:
1. Define product categories
First, you need to define a complex object with multiple attributes or components, namely a product class.
2. Define the abstract builder class
Next, you need to define an abstract builder class or interface that contains abstract methods for creating various parts of the product object.
3. Define specific builder categories
Then, one or more concrete builder classes need to be defined, which are subclasses of the abstract builder class, implement the abstract methods defined in the abstract builder class, and assemble various parts of the product object according to the specific needs.
4. Define the instructor class
Finally, a mentor class needs to be defined, which is responsible for creating instances of the specific builder class and calling methods in the specific builder class to assemble parts of the product object. In practical applications, only one instructor class is usually needed.
5. Create an object using builder pattern
Finally, we can use the builder pattern to create an object, that is, we first create an instance of the specific builder class, and then hand the instance over to the instructor class for assembly, and finally get a complete product object.
Builder builder = new ConcreteBuilder(); Director director = new Director(); (builder); Product product = ();
The above is the implementation method of the builder model. Let’s introduce its application scenarios below.
Application scenarios
Builder mode is suitable for the following scenarios:
1. The object construction process is relatively complex
When the objects that need to be created are more complex and need to be generated through multiple steps, you can use the builder pattern.
2. Objects with different representations need to be generated
When you need to create objects in different logical orders, or when you need to generate objects with different representations, you can use the builder pattern.
3. The construction process and representation of the object you want to separate
Builder pattern can be used when you want to separate the build process and specific representation of an object.
For example, in Java, StringBuilder uses the builder pattern. In programs, we often need to splice strings. If we use the String type to splice strings, each splicing will create a new String object, which will waste a lot of memory. Instead, using StringBuilder, it adds the required strings one by one and assembles them into a complete string object when needed, thus avoiding unnecessary memory waste.
In addition, in Java, the Calendar class provided in JDK also uses the builder pattern. When creating a date and time object, you need to set information such as year, month, day, hour, minute, and second. If you use ordinary constructors or setter methods to set this information, the code will become lengthy and difficult to maintain. By using the builder pattern provided by the Calendar class, these settings information can be broken down into multiple simple steps and assembled in a certain order, thereby realizing the creation of date and time objects.
Summarize
Through the introduction of this article, we understand the builder model in Java, including its definition, structure, implementation methods, and application scenarios. The builder pattern breaks down the construction process of an object into a construction process of multiple simple objects and assembles it in a certain order, ultimately realizing the creation of complex objects. By using the builder pattern, the object's construction process and specific build implementations can be separated, thereby improving the maintainability and readability of the code.
This is the end of this article about the detailed explanation of the builder model of Java Creative Design Pattern. For more related content on Java Builder Model, please search for my previous articles or continue browsing the related articles below. I hope everyone will support me in the future!