Builder模式

  如果一个类的构造器或者静态工场中有多个参数，使用Builder模式。

 

public class Lunch {
    private String cake;
    private String milk;
    private String meat;
    private String drink;
    
    public static class Builder{
        private String cake;
        private String milk;
        private String meat;
        private String drink;
        
        public Builder(){
            
        }
        public Builder addCake(String cake){
            this.cake = cake;
            return this;
        }
        public Builder addMilk(String milk){
            this.milk = milk;
            return this;
        }
        public Builder addMeat(String meat){
            this.meat = meat;
            return this;
        }
        public Builder addDrink(String drink){
            this.drink = drink;
            return this;
        }
        public Lunch create(){
            return new Lunch(this);
        }
    }
    private Lunch(Builder builder){
        this.cake = builder.cake;
        this.drink = builder.drink;
        this.meat = builder.meat;
        this.milk = builder.milk;
    }
    public String toString() {
        // TODO Auto-generated method stub
        return "==" + meat + "==" + cake + "==" + milk + "==" + drink;  
    }
}

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