请问下面的代码属于什么设计?为什么把set方法改成那样子
public class A{
private Integer num;
private String min;
public Integer gerNum(){
return num;
}
public A num(Integer num){
this.num = num;
return this;
}
public String getMin(){
return min;
}
public A min(String min){
this.min = min;
return this;
}
}