java中的builder模式

import android.text.TextUtils;

/**
 * Created by toothwind on 2017/7/19.
 * you can contact me at : toothwind@163.com.
 * All Rights Reserved
 */
public class Demo {

    //属性
    private String age;
    private String height;
    private String salary;

    //构造
    private Demo(Builder builder) {
        this.age = builder.age;
        this.height = builder.height;
        this.salary = builder.salary;
    }

    //对外方法
    public String age() {
        return age;
    }

    //对外方法
    public String height() {
        return height;
    }

    //对外方法
    public String salary() {
        return salary;
    }

    public Builder newBuilder() {
        return new Builder(this);
    }

    @Override
    public String toString() {
        return "Demo{" +
                "age='" + age + '\'' +
                ", height='" + height + '\'' +
                ", salary='" + salary + '\'' +
                '}';
    }

    public static class Builder {
        private String age;
        private String height;
        private String salary;

        public Builder() {
            this.age = "18";
        }

        private Builder(Demo demo) {
            this.age = demo.age;
            this.height = demo.height;
            this.salary = demo.salary;
        }

        public Builder age(String age) throws Exception {
            if (TextUtils.isEmpty(age)) {
                throw new Exception("年龄不能为空");
            }
            this.age = age;
            return this;
        }

        public Builder height(String height) throws Exception {
            if (TextUtils.isEmpty(height)) {
                throw new Exception("身高不能为空");
            }
            this.height = height;
            return this;
        }

        public Builder salary(String salary) throws Exception {
            this.salary = salary;
            return this;
        }

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

    }


}