Build模式

Builder模式，意思是我们new 对象的时候附带构造方法，如果里面的成员变量太多的话，我们根本不知道他是代表什么意思，由此我们可引入静态内部类类Builder类，可阅读性就明显提高了。

下面是实体类的构造方式，加入build类

public class UserDTO {    private long id;    private String userName;    private String loginName;    private String sex;    private double height;    private double weight;    public UserDTO() {    }    public UserDTO(long id, String userName, String loginName, String sex, double height, double weight) {        this.id = id;        this.userName = userName;        this.loginName = loginName;        this.sex = sex;        this.height = height;        this.weight = weight;    }    public long getId() {        return id;    }    public void setId(long id) {        this.id = id;    }    public String getUserName() {        return userName;    }    public void setUserName(String userName) {        this.userName = userName;    }    public String getLoginName() {        return loginName;    }    public void setLoginName(String loginName) {        this.loginName = loginName;    }    public String getSex() {        return sex;    }    public void setSex(String sex) {        this.sex = sex;    }    public double getHeight() {        return height;    }    public void setHeight(double height) {        this.height = height;    }    public double getWeight() {        return weight;    }    public void setWeight(double weight) {        this.weight = weight;    }    private UserDTO(Builder builder) {        this.id = builder.id;        this.userName = builder.userName;        this.loginName = builder.loginName;        this.sex = builder.sex;        this.height = builder.height;        this.weight = builder.weight;    }    //静态内部Builder类    static class Builder {        private long id;        private String userName;        private String loginName;        private String sex;        private double height;        private double weight;        public Builder setId(long id) {            this.id = id;            return this;        }        public Builder setUserName(String userName) {            this.userName = userName;            return this;        }        public Builder setLoginName(String loginName) {            this.loginName = loginName;            return this;        }        public Builder setSex(String sex) {            this.sex = sex;            return this;        }        public Builder setHeight(double height) {            this.height = height;            return this;        }        public Builder setWeight(double weight) {            this.weight = weight;            return this;        }        public UserDTO build() {            return new UserDTO(this);        }    }}

这个时候 我们在其他地方new对象的时候就是这样子的

public class MainActivity extends AppCompatActivity {    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        UserDTO.Builder builder = new UserDTO.Builder();        UserDTO userDTO = builder                .setId(1L)                .setUserName("user")                .setLoginName("admin")                .setHeight(170.00)                .setWeight(60.00)                .setSex("男")                .build();    }}

这样子 每个成员变量是不是都比较清晰了，像OKkttp的构造方法也是类似的这个的。

当然我们也可以直接使用

AA aa=new AA();

aa.setXX(XX);这个方法了