Builder Pattern in java

 In Builder pattern, we have a inner static class named Builder inside our Server class with instance fields for that class and also have a factory method to return an new instance of Builder class on every invocation. The setter methods will now return Builder class reference. We will also have a build method to return instances of Server side class, i.e. outer class.

The builder pattern is a design pattern designed to provide a flexible solution to various object creation problems in object-oriented programming. The intent of the Builder design pattern is to separate the construction of a complex object from its representation. It is one of the Gang of Four design patterns.

class Student { private final int id; private final String name; private final String address; private Student(Builder builder) { this.id = builder.id; this.name = builder.name; this.address = builder.address; } // Static class Builder public static class Builder { private int id; private String name; private String address; public static Builder newInstance() { return new Builder(); } private Builder() {} public Builder setId(int id) { this.id = id; return this; } public Builder setName(String name) { this.name = name; return this; } public Builder setAddress(String address) { this.address = address; return this; } public Student build() { return new Student(this); } } @Override public String toString() { return "id = " + this.id + ", name = " + this.name + ", address = " + this.address; } } public class BuilderDemo { public static void main(String args[]) { Student student = Student.Builder.newInstance().setId(7).setName("abc").setAddress("def").build(); System.out.println(student.toString()); } }