build设计模式

又叫生成器模式

public class MainActivity extends AppCompatActivity {

    TextView textView;
    Button button;
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        textView = findViewById(R.id.text);
        button = findViewById(R.id.button);

        Student.Builder builder = new Student.Builder();
        String address = builder.address("北京").name("四环").build().getAddress();
        System.out.println(address);
    }
    }

public class Student {

    private int id;
    private String name;
    private String passwd;
    private String sex;
    private String address;

    // 构造器尽量缩小范围
    private Student() {
    }

    // 构造器尽量缩小范围
    private Student(Student origin) {
        // 拷贝一份
        this.id = origin.id;
        this.name = origin.name;
        this.passwd = origin.passwd;
        this.sex = origin.sex;
        this.address = origin.address;
    }

    public int getId() {
        return id;
    }

    public String getName() {
        return name;
    }

    public String getPasswd() {
        return passwd;
    }

    public String getSex() {
        return sex;
    }

    public String getAddress() {
        return address;
    }

    /**
     * Student的创建完全依靠Student.Builder，使用一种方法链的方式来创建
     *
     */
    public static class Builder {

        private Student target;

        public Builder() {
            target = new Student();
        }

        public Builder address(int id) {
            target.id = id;
            return this;
        }

        public Builder name(String name) {
            target.name = name;
            return this;
        }

        public Builder password(String passwd) {
            target.passwd = passwd;
            return this;
        }

        public Builder sex(String sex) {
            target.sex = sex;
            return this;
        }

        public Builder address(String address) {
            target.address = address;
            return this;
        }

        public Student build() {
            return new Student(target);
        }

    }

}