Builder模式的目的是解耦构建过程，为什么要用内部类？

还没有看过Builder模式的作用，看过一篇介绍Builder模式的文章，这里是关于Builder模式的思考：思考是否有比新建一个内部类更好的方法，首先想到的是

package xyz.n490808114.test;
public class  BuilderTest{
    String name;
    int age;
    int high;
    int weight;
    int speed;

    public BuilderTest name(String name){
        this.name = name;
        return this;
    }
    public BuilderTest age(int age){
        this.age = age;
        return this;
    }
    public BuilderTest high(int high){
        this.high = high;
        return this;
    }
    public BuilderTest weight(int weight){
        this.weight = weight;
        return this;
    }
    public BuilderTest speed(int speed){
        this.speed = speed;
        return this;
    }
    public void setName(String name){this.name = name;}
    public void setAge(int age){this.age = age;}
    public void setHigh(int high){this.high = high;}
    public void setWeight(int weight){this.weight = weight;}
    public void setSpeed(int speed){this.speed = speed;}
    public String getName(){return this.name;}
    public int getAge(){return this.age;}
    public int getHigh(){return this.high;}
    public int getWeight(){return this.weight;}
    public int getSpeed(){return this.speed;}
    public static void main(String[] args) {
        BuilderTest t = new BuilderTest().age(20).speed(50);
        System.out.println(t.name);
        System.out.println(t.age);
        System.out.println(t.high);
        System.out.println(t.weight);
        System.out.println(t.speed);
    }
}

输出为

null
20
0
0
50

这样感觉跟set方法重复太多，整合一下，如下

package xyz.n490808114.test;
public class  BuilderTest{
    String name;
    int age;
    int high;
    int weight;
    int speed;
    public BuilderTest setName(String name){this.name = name;return this;}
    public BuilderTest setAge(int age){this.age = age;return this;}
    public BuilderTest setHigh(int high){this.high = high;return this;}
    public BuilderTest setWeight(int weight){this.weight = weight;return this;}
    public BuilderTest setSpeed(int speed){this.speed = speed;return this;}
    public String getName(){return this.name;}
    public int getAge(){return this.age;}
    public int getHigh(){return this.high;}
    public int getWeight(){return this.weight;}
    public int getSpeed(){return this.speed;}
    public static void main(String[] args) {
        BuilderTest t = new BuilderTest().setAge(20).setSpeed(50);
        System.out.println(t.name);
        System.out.println(t.age);
        System.out.println(t.high);
        System.out.println(t.weight);
        System.out.println(t.speed);
    }
}

这样只是精简代码，只是不知道这样的set方法能不能被spring认可，待测试

能够想到的是：

1，Builder模式用内部类的方法，可以用来修改现有代码，不改动，不新增类的方法，仅在创建时使用内部类；

2，猜测：如果不是频繁创建的话，对性能的影响不大；

3，如果不采用模式，仅使用set方法的话，代码量会多，但是代码会更清晰；

4，Builder模式使代码更易阅读。

Builder模式

package xyz.n490808114.test;
public class BuilderTest{
    String name;
    int age;
    int high;
    int weight;
    int speed;
    public BuilderTest(Builder builder){
        this.name = builder.name;
        this.age = builder.age;
        this.high = builder.high;
        this.weight = builder.weight;
        this.speed = builder.speed;
    }
    public void setName(String name){this.name = name;}
    public void setAge(int age){this.age = age;}
    public void setHigh(int high){this.high = high;}
    public void setWeight(int weight){this.weight = weight;}
    public void setSpeed(int speed){this.speed = speed;}
    public String getName(){return this.name;}
    public int getAge(){return this.age;}
    public int getHigh(){return this.high;}
    public int getWeight(){return this.weight;}
    public int getSpeed(){return this.speed;}

    public static class Builder{
        String name;
        int age;
        int high;
        int weight;
        int speed;
        public Builder name(String name){
            this.name = name;
            return this;
        }
        public Builder age(int age){
            this.age = age;
            return this;
        }
        public Builder high(int high){
            this.high = high;
            return this;
        }
        public Builder weight(int weight){
            this.weight = weight;
            return this;
        }
        public Builder speed(int speed){
            this.speed = speed;
            return this;
        }
        public BuilderTest build(){
            return new BuilderTest(this);
        }
    }
    public static void main(String[] args) {
        BuilderTest t = new BuilderTest.Builder().age(20).speed(50).build();
        BuilderTest s = new BuilderTest.Builder().age(120).speed(150).build();
        System.out.println(t.name);
        System.out.println(t.age);
        System.out.println(t.high);
        System.out.println(t.weight);
        System.out.println(t.speed);
        System.out.println(s.name);
        System.out.println(s.age);
        System.out.println(s.high);
        System.out.println(s.weight);
        System.out.println(s.speed);
    }
}

输出为

null
20
0
0
50
null
120
0
0
150