Foo foo = Foo.builder()
.setColor(red)
.setName("Fred")
.setSize(42)
.build();
So I know there is the following "Builder" solution for creating named parameters when calling a method. Although, this only seems to work with inner static classes as the builder or am I wrong? I had a look at some tutorials for builder pattern but they seem really complex for what im trying to do. Is there any way to keep the Foo class and Builder class separate while having the benefit of named parameters like the code above?
Below a typical setup:
public class Foo {
public static class Builder {
public Foo build() {
return new Foo(this);
}
public Builder setSize(int size) {
this.size = size;
return this;
}
public Builder setColor(Color color) {
this.color = color;
return this;
}
public Builder setName(String name) {
this.name = name;
return this;
}
// you can set defaults for these here
private int size;
private Color color;
private String name;
}
public static Builder builder() {
return new Builder();
}
private Foo(Builder builder) {
size = builder.size;
color = builder.color;
name = builder.name;
}
private final int size;
private final Color color;
private final String name;
}
Use composition. To make things easier and cleaner, do not replicate all attributes in source (Foo) and builder (Builder) class.
For example, have Foo class inside Builder instead of each of Foo attribute.
simple code snippet:
import java.util.*;
class UserBasicInfo{
String nickName;
String birthDate;
String gender;
public UserBasicInfo(String name,String date,String gender){
this.nickName = name;
this.birthDate = date;
this.gender = gender;
}
public String toString(){
StringBuilder sb = new StringBuilder();
sb.append("Name:DOB:Gender:").append(nickName).append(":").append(birthDate).append(":").
append(gender);
return sb.toString();
}
}
class ContactInfo{
String eMail;
String mobileHome;
String mobileWork;
public ContactInfo(String mail, String homeNo, String mobileOff){
this.eMail = mail;
this.mobileHome = homeNo;
this.mobileWork = mobileOff;
}
public String toString(){
StringBuilder sb = new StringBuilder();
sb.append("email:mobile(H):mobile(W):").append(eMail).append(":").append(mobileHome).append(":").append(mobileWork);
return sb.toString();
}
}
class FaceBookUser {
String userName;
UserBasicInfo userInfo;
ContactInfo contactInfo;
public FaceBookUser(String uName){
this.userName = uName;
}
public void setUserBasicInfo(UserBasicInfo info){
this.userInfo = info;
}
public void setContactInfo(ContactInfo info){
this.contactInfo = info;
}
public String getUserName(){
return userName;
}
public UserBasicInfo getUserBasicInfo(){
return userInfo;
}
public ContactInfo getContactInfo(){
return contactInfo;
}
public String toString(){
StringBuilder sb = new StringBuilder();
sb.append("|User|").append(userName).append("|UserInfo|").append(userInfo).append("|ContactInfo|").append(contactInfo);
return sb.toString();
}
static class FaceBookUserBuilder{
FaceBookUser user;
public FaceBookUserBuilder(String userName){
this.user = new FaceBookUser(userName);
}
public FaceBookUserBuilder setUserBasicInfo(UserBasicInfo info){
user.setUserBasicInfo(info);
return this;
}
public FaceBookUserBuilder setContactInfo(ContactInfo info){
user.setContactInfo(info);
return this;
}
public FaceBookUser build(){
return user;
}
}
}
public class BuilderPattern{
public static void main(String args[]){
FaceBookUser fbUser1 = new FaceBookUser.FaceBookUserBuilder("Ravindra").build(); // Mandatory parameters
UserBasicInfo info = new UserBasicInfo("sunrise","25-May-1975","M");
// Build User name + Optional Basic Info
FaceBookUser fbUser2 = new FaceBookUser.FaceBookUserBuilder("Ravindra").
setUserBasicInfo(info).build();
// Build User name + Optional Basic Info + Optional Contact Info
ContactInfo cInfo = new ContactInfo("xxx@xyz.com","1111111111","2222222222");
FaceBookUser fbUser3 = new FaceBookUser.FaceBookUserBuilder("Ravindra").
setUserBasicInfo(info).
setContactInfo(cInfo).build();
System.out.println("Facebook user 1:"+fbUser1);
System.out.println("Facebook user 2:"+fbUser2);
System.out.println("Facebook user 3:"+fbUser3);
}
}
output:
Facebook user 1:|User|Ravindra|UserInfo|null|ContactInfo|null
Facebook user 2:|User|Ravindra|UserInfo|Name:DOB:Gender:sunrise:25-May-1975:M|ContactInfo|null
Facebook user 3:|User|Ravindra|UserInfo|Name:DOB:Gender:sunrise:25-May-1975:M|ContactInfo|email:mobile(H):mobile(W):xxx@xyz.com:1111111111:2222222222
Explanation:
FaceBookUser is a complex object with below attributes using composition:
String userName;
UserBasicInfo userInfo;
ContactInfo contactInfo;
FaceBookUserBuilder is a static builder class, which contains and builds FaceBookUser.
userName is only Mandatory parameter to build FaceBookUser
FaceBookUserBuilder builds FaceBookUser by setting optional parameters : UserBasicInfo and ContactInfo
This example illustrates three different FaceBookUsers with different attributes, built from Builder.
In this example, composition has been used instead of duplicating all attributes of FaceBookUser in Builder class.
EDIT:
Group all related attributes into logical classes. Define all these classes in FaceBookUser. Instead of adding all these member variables again in Builder, contain FaceBookUser in Builder class.
For simplicity, I have added two classes: UserBasicInfo and ContactInfo . Now explode this FaceBookUser class with other attributes like
NewsFeed
Messages
Friends
Albums
Events
Games
Pages
Ads
etc.
If you duplicate all these attributes in both Builder and FaceBookUser, code will become difficult to manage. Instead, by using composition of FaceBookUser in FaceBookUserBuilder itself, you can simply construction process.
Once you add above attributes, you will build FaceBookUser in step-by-step process as usual.
It will be like this:
FaceBookUser fbUser3 = new FaceBookUser.FaceBookUserBuilder("Ravindra").
setUserBasicInfo(info).
setNewsFeed(newsFeed).
setMessages(messages).
setFriends(friends).
setAlbums(albums).
setEvents(events).
setGames(games).
setAds(ads).build();