原型模式
public class MainActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Student student = new Student();
student.name = "我的世界";
student.student_id = "123465";
ArrayList<Teacher> list = new ArrayList<>();
for (int i = 0; i < 5; i++) {
Teacher teacher = new Teacher();
teacher.id = "" + i;
teacher.name = "--" + i + "--";
list.add(teacher);
}
student.teachers = list;
clone_0(student);
// setData(student);
}
/**
* clone 模式测试
*
*/
/**
* 1 赋值模式
*
* @param student log 结果
* setData: name = 我的世界
* onCreate: student = app.yjkm.com.day_03.Student@125b76ef
* onCreate: student1 = app.yjkm.com.day_03.Student@125b76ef
* setData: student.name = student1
* setData: student1.name = student1
* <p>
* 可以看到student 和student1其实在堆中保存的地址是一样的
* 说明student 和student1 持有的地址引用是一样的
* 所以在student1 改名后student的名字也会改变
*/
private void setData(Student student) {
String name = student.name;
Student student1 = student;
student1.name = "student1";
Log.e("text123", "setData: name = " + name);
Log.e("text123", "onCreate: student = " + student);
Log.e("text123", "onCreate: student1 = " + student1);
Log.e("text123", "setData: student.name = " + student.name);
Log.e("text123", "setData: student1.name = " + student1.name);
}
/**
* 浅拷贝
*
* @param student clone_0: name = 我的世界
* clone_0: student = app.yjkm.com.day_03.Student@125b76ef
* clone_0: StudentClone = app.yjkm.com.day_03.Student@1b08a5fc
* clone_0: student.name = 我的世界
* clone_0: student1.name = 浅拷贝
* clone_0: teachers = []
* clone_0: teachers1 = []
*
* 可以看到student和studentClone 所持有引用的地址是不一样的
* 所以 student和studentClone是两个类了 所以当studentClone的name修改的时候
* student的name 是没有受到影响
*
* 但是在student的teachers和studentClone 的 teachers 缺还是持有的同一个地址
* 如果在复写clone函数的时候也是用的teacher的clone函数才会把student里面的
* teacher类也clone那就是深拷贝了
*
* 深拷贝
* clone_0: teachers = [
* app.yjkm.com.day_03.Teacher@229a485,
* app.yjkm.com.day_03.Teacher@1fb9c2da,
* app.yjkm.com.day_03.Teacher@2a12930b,
* app.yjkm.com.day_03.Teacher@183825e8,
* app.yjkm.com.day_03.Teacher@24e50401]
*
* clone_0: teachers1 = []
*
*/
private void clone_0(Student student) {
String name = student.name;
Student StudentClone = student.clone();
StudentClone.name = "浅拷贝";
Log.e("text123", "clone_0: name = " + name);
Log.e("text123", "clone_0: student = " + student);
Log.e("text123", "clone_0: StudentClone = " + StudentClone);
Log.e("text123", "clone_0: student.name = " + student.name);
Log.e("text123", "clone_0: student1.name = " + StudentClone.name);
List<Teacher> teachers = student.teachers;
List<Teacher> teachers1 = StudentClone.teachers;
teachers1.clear();
Log.e("text123", "clone_0: teachers = " + teachers);
Log.e("text123", "clone_0: teachers1 = " + teachers1);
}
}
优点
原型模式是在内存中二进制流的拷贝,要比直接new一个对象性能要好很多
特别是要在一个循环体内产生大量对象的时候,原型模式可以更好的体现其优点
缺点
直接在内存中拷贝 是不会执行构造函数的,在实际开发中要注意这个潜在的问题
优点是减少约束缺点是少了约束
代码地址
