builder模式

最新推荐文章于 2025-06-02 02:55:40 发布

原创最新推荐文章于 2025-06-02 02:55:40 发布 · 297 阅读

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本文探讨了在Java类中使用不同构造方法、setter方法及Builder模式来初始化对象的优缺点。通过示例展示了每种方法的实现方式，特别是Builder模式如何解决构造方法在面对多个参数时的不足。

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当某个类中有多个参数时，如果在构造方法中提供参数的设置，将会出现数量众多的组合，代码可读性会非常差

此处例子只有3个参数，构造方法已经众多，并且还有参数类型之间的冲突问题

public class Student {

    private Long id;
    private String name;
    private String phoneNumber;
    //......

    public Student() {
    }

    public Student(Long id) {
        this.id = id;
    }

    public Student(String name) {
        this.name = name;
    }

    public Student(String name, String phoneNumber) {
        this.name = name;
        this.phoneNumber = phoneNumber;
    }

    public Student(Long id, String name) {
        this.id = id;
        this.name = name;
    }

    public Student(Long id, String name, String phoneNumber) {
        this.id = id;
        this.name = name;
        this.phoneNumber = phoneNumber;
    }
    //......

}

改用set方法来优化：

public class Student {

    private Long id;
    private String name;
    private String phoneNumber;

    public Student() {
    }

    public void setId(Long id) {
        this.id = id;
    }

    public void setName(String name) {
        this.name = name;
    }

    public void setPhoneNumber(String phoneNumber) {
        this.phoneNumber = phoneNumber;
    }

}

在使用时：

   Student student = new Student();
   student.setId(123L);
   student.setName("name");
   student.setPhoneNumber("123456");

但是，set方法在使用时会有线程安全的问题

假如上述代码块在执行到setId时student就被另一线程调用，此时Name和PhoneNubmer就会为null，而如果给student加锁，则会影响性能，改用builder则能解决这些问题:

public class Student {

    private Long id;
    private String name;
    private String phoneNumber;

    private Student(StudentBuiler builer) {
        this.id = builer.id;
        this.name = builer.name;
        this.phoneNumber = builer.phoneNumber;
    }

    public static class StudentBuiler {
        private Long id;
        private String name;
        private String phoneNumber;

        public StudentBuiler id(Long id) {
            this.id = id;
            return this;
        }

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

        public StudentBuiler phoneNumber(String phoneNumber) {
            this.phoneNumber = phoneNumber;
            return this;
        }

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

}

在调用时的代码也简洁明了：

  Student student = new Student.StudentBuiler().id(123L).name("name").phoneNumber("123456").build();