利用Builder方式创建对象示例代码

前言

在创建对象需要初始化数据，数据参数不容易区别，可传可不传的时候，可以考虑使用Builder建造方法创建。每每当看到别人写的用Bulder方式来调用，就觉得so cool，那就自己也来用Builder方式创建对象吧。

下面话不多说了，来一起看看详细的介绍吧

现在要录入一系列人员的基本信息的示例：

创建Person类

public class Person {private String name;private int age;private float height;private float weight;public Person(String name, int age, float height, float weight) {this.name = name;this.age = age;this.height = height;this.weight = weight;}public String getName() {return name;}public void setName(String name) {this.name = name;}public int getAge() {return age;}public void setAge(int age) {this.age = age;}public float getHeight() {return height;}public void setHeight(float height) {this.height = height;}public float getWeight() {return weight;}public void setWeight(float weight) {this.weight = weight;}}

那么创建对象就是这样，后面参数不容易看出表示的是什么，可读性不强

new Person("冯提莫",18,150,43);new Person("温婉",17,164,48);

用Builder模式进行改造

创建一个Builder类，属性和Person类一样，加上SetXxx()方法

static class Builder{private String name;private int age;private float height;private float weight;public void setName(String name) {this.name = name;}public void setAge(int age) {this.age = age;}public void setHeight(float height) {this.height = height;}public void setWeight(float weight) {this.weight = weight;}}

将Person的构造方法改为传入Builder对象，将Builder对象的属性值都赋予Person对象

public Person(Builder builder){this.name = builder.name;this.age = builder.age;this.height = builder.height;this.weight = builder.weight;}

改造Builder类，关键步骤是将各个set方法返回Builder类对象，这样就能继续愉快地连续调用set方法了，最后调用build()创建方法返回Person对象。

static class Builder{private String name;private int age;private float height;private float weight;public Builder setName(String name) {this.name = name;return this;}public Builder setAge(int age) {this.age = age;return this;}public Builder setHeight(float height) {this.height = height;return this;}public Builder setWeight(float weight) {this.weight = weight;return this;}public Person build(){return new Person(this);}}

将各个set方法的返回值类型改为Builder，每次都返回builder对象，这样才能将set方法实现连续的链式调用。

build()方法创建一个person对象，会调用Person的带参构造方法，将builder对象的属性依次赋予person对象。person中的属性值就是链式调用set方法的各个值。