Java对象创建与Builder模式-优快云博客

一、创建、销毁对象

1、考虑用静态工厂方法替代构造器

2、遇到多个构造器参数时要考虑用构建器

静态工厂和构造器有一个共同的局限性，它们不能很好的扩展到大量的可选参数，程序员一向习惯采用重叠构造器，在这种模式下，提供第一个只有必要参数的构造器，第二个构造器有一个可选参数，最后一个构造器包含所有的可选参数。

public People(String name,String sex){
  this(name,sex,0,0,0,"");
}
public People(String name,String sex,int age){
  this(name,sex,age,0,0,"");
}
public People(String name,String sex,int age,float height,float wigth){
  this(name,sex,age,height,wigth,"");
}
public People(String name,String sex,int age,float height,float wigth,String skin){
  this.name=name;
  this.sex=sex;
  this.age=age;
  this.height=height;
  this.wigth=wigth;
  this.skin=skin;
}

重叠的构造器方法可行，但是当有许多参数的时候，代码很难编写，并且难以阅读。

Builder方法：

public class People {
    private final String name;
    private final String sex;
    private final String address;
    private final float height;
    private final float weight;

    public People(Builder builder) {
        name = builder.name;
        sex = builder.sex;
        address = builder.address;
        height = builder.height;
        weight = builder.weight;
    }
}

public class Builder {
    public String name;
    public String sex;
    public String address;
    public float height;
    public float weight;

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

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

    public Builder setHeight(float height) {
        this. height = height;
        return this;
    }

    public Builder setWeight(float weight) {
        this.weight = weight;
        return this;
    }

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


public class MainClass {
    public static void main(String[] args){
        People people = new Builder("pxc","女").setAddress("福州").setHeight(163).setWeight(45).build();
       
    }
}

运行结果：通过builder方法把参数写入对象中。