建造者模式

1.概念

建造者模式是一种创建型设计模式，它允许我们一步一步的来构造对象，其实就是将创建对象的一个过程拆分成了很多个小步骤，常见主要是在一个A类的基础上，加多一个Builder的类，然后属性和A类的一样，我们在创建A类的对象时不直接通过new A()的形式，而是通过new Builder（）创建一个Builder对象，然后调用各个方法去设置Builder对象属性最后再去new A()对象,并且各个属性的值均从Builder对象里取。

2.Cat类

package com.yl.pattern.builder;

public class Cat {
    private long id;
    private String name;
    private int age;
    private String gender;

    public Cat(long id,String name,int age,String gender) {
        this.id = id;
        this.name = name;
        this.age = age;
        this.gender = gender;
    }

    @Override
    public String toString() {
        return "id=" + id + ",name=" + name +",age=" + age + ",gender=" + gender;
    }
}

3.Cat Builder

package com.yl.pattern.builder;

public class CatBuilder {
    private long id;
    private String name;
    private int age;
    private String gender;

    public CatBuilder setId(long id) {
        this.id = id;
        return this;
    }

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

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


    public CatBuilder setGender(String gender) {
        this.gender = gender;
        return this;
    }

    public Cat build() {
        return new Cat(id,name,age,gender);
    }

}

4.demo

package com.yl.pattern.builder;

public class Demo {
    public static void main(String[] args) {
        CatBuilder catBuilder = new CatBuilder();
        Cat cat = catBuilder.setId(1).setName("小鱼").setAge(18).setGender("male").build();
        System.out.println(cat);
    }
}