Java builder design pattern example

By mkyong | Updated: March 18, 2016

Viewed: 618 (+8 pv/w)

Tags: builder design pattern java

A complete Java builder pattern example.

package com.mkyong.model;

import java.util.List;

public class Student {

    private String name;
    private int age;
    private List<String> language;

    public static class Builder {

        private String name;
        private int age;
        private List<String> language;

        public Builder name(String name) {
            this.name = name;
            return this;
        }

        public Builder age(int age) {
            this.age = age;
            return this;
        }

        public Builder language(List<String> language) {
            this.language = language;
            return this;
        }

        public Student build() {
            return new Student(this);
        }

    }

    private Student(Builder builder) {
        name = builder.name;
        age = builder.age;
        language = builder.language;
    }

    @Override
    public String toString() {
        return "Student{" +
                "name='" + name + '\'' +
                ", age=" + age +
                ", language=" + language +
                '}';
    }
}

Example to use above builder pattern to create a Student object.

package com.mkyong.model;

import java.util.Arrays;

public class TestStudent {

    public static void main(String[] args) {

        Student s = new Student.Builder()
			.name("mkyong")
			.age(18)
			.language(Arrays.asList("chinese","english"))
			.build();

		//Student{name='mkyong', age=18, language=[chinese, english]}
        System.out.println(s);

        // Classic way to create an object
		/*
		Student s = new Student();
        s.setName("mkyong");
        s.setAge(18);
        s.setLanguage(Arrays.asList("chinese","english"));
		*/

    }

}

References

1. Wikipedia – Builder pattern
2. Too Many Parameters in Java Methods, Part 3: Builder Pattern