JAVA构建器Builder模式

/**
* 构建器Builder模式
* Android中的AlertDialog的构建器模式
*/
public class Lunch {
private String cake;
private String meat;
private String milk;
private String drink;

public static class Builder{
private String meat; //必须要初始化的参数
private String cake;
private String milk;
private String drink;

public Builder(String meat){
this.meat = meat;
}

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

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

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

public Lunch create(){
return new Lunch(this);
}
}

private Lunch(Builder builder){
this.meat = builder.meat;
this.cake = builder.cake;
this.milk = builder.milk;
this.drink = builder.drink;
}

@Override
public String toString() {
return "Lunch [cake=" + cake + ", drink=" + drink + ", meat=" + meat
+ ", milk=" + milk + "]";
}

public static void main(String[] args) {
Lunch.Builder builder = new Lunch.Builder("meat");
Lunch lunch = builder.addCake("cake")
.addDrink("drink")
//.addMilk("milk")
.create();
System.out.println(lunch.toString());
}
}