前言

在創(chuàng)建對象需要初始化數(shù)據(jù)，數(shù)據(jù)參數(shù)不容易區(qū)別，可傳可不傳的時候，可以考慮使用Builder建造方法創(chuàng)建。每每當(dāng)看到別人寫的用Bulder方式來調(diào)用，就覺得so cool，那就自己也來用Builder方式創(chuàng)建對象吧。

下面話不多說了，來一起看看詳細的介紹吧

現(xiàn)在要錄入一系列人員的基本信息的示例：

創(chuàng)建Person類

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;}}

那么創(chuàng)建對象就是這樣，后面參數(shù)不容易看出表示的是什么，可讀性不強

new Person("馮提莫",18,150,43);new Person("溫婉",17,164,48);

用Builder模式進行改造

創(chuàng)建一個Builder類，屬性和Person類一樣，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;}}

將Person的構(gòu)造方法改為傳入Builder對象，將Builder對象的屬性值都賦予Person對象

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

改造Builder類，關(guān)鍵步驟是將各個set方法返回Builder類對象，這樣就能繼續(xù)愉快地連續(xù)調(diào)用set方法了，最后調(diào)用build()創(chuàng)建方法返回Person對象。

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);}}

將各個set方法的返回值類型改為Builder，每次都返回builder對象，這樣才能將set方法實現(xiàn)連續(xù)的鏈?zhǔn)秸{(diào)用。

build()方法創(chuàng)建一個person對象，會調(diào)用Person的帶參構(gòu)造方法，將builder對象的屬性依次賦予person對象。person中的屬性值就是鏈?zhǔn)秸{(diào)用set方法的各個值。