@Builder参数值改变UI没有刷新问题，代码如下，点击按钮“年龄+1”,年龄数值并没有发生改变，是什么原因呢

class Student {
  age: number = 0

  constructor(age: number) {
    this.age = age
  }
}
@Component
export struct Component19 {
  @State student: Student = new Student(20)

  build() {
    Column() {
      this.StudentBuilder(this.student)
    }.width("100%")
    .padding(10)
  }

  @Builder
  StudentBuilder(student: Student) {
    Text(student.age + "")
    Button("年龄+1").onClick(() => {
      student.age++
    })
  }
}

class Student {
  age: number = 0

  constructor(age: number) {
    this.age = age
  }
}

@Component
export struct Component19 {
  @State student: Student = new Student(20)

  build() {
    Column() {
      this.StudentBuilder()
    }.width("100%")
    .padding(10)
  }

  @Builder
  StudentBuilder() {
    Text(this.student.age + "")
    Button("年龄+1").onClick(() => {
      this.student.age++
    })
  }
}