建造者模式（Builder）用以自由构建对象，主要功能就是代替对象的构造函数，更加自由化。

案例：

/**
 * @author Gjing
 **/
class Custom {
    private Integer age;
    private String name;
    private String address;

    static Custom.Builder builder(){
        return new Custom.Builder();
    }

    private Custom(Builder builder) {
        this.age = builder.age;
        this.name = builder.name;
        this.addr