构建器使用举例-静态工厂和构造器的替代方法

“静态工厂和构造器有个共同的局限性：他们都不能很好的扩展到大量的可选参数。”

下面是构建器的一个举例：

package com.bestcxx.stu.builder;

/**
* 只能通过构造器方法对实体进行值的修改
* @author Administrator
*
*/
public class UserBuilder {

private final int number;
private final int name;
private final int age;

public static class Builder{

private final int number;

//设置默认值
private int name=0;
private int age=0;

public Builder(int number){
this.number=number;
}

public Builder name(int val){
name=val;return this;
}

public Builder age(int val){
age=val;return this;
}

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

}

private UserBuilder(Builder builder){
number=builder.number;
name=builder.name;
age=builder.age;
}

public static void main(String[] args) {
UserBuilder u=new UserBuilder.Builder(1).name(10).age(20).build();
System.out.println(u.number);
System.out.println(u.age);
System.out.println(u.name);

}

}