Java 中创建对象的方式

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1. 使用new关键字创建对象

Student stu = new Student();

2. 使用Class类的newInstance方法（反射机制）

// 调用无参的构造器创建对象
Student stu = (Student) Class.forName("Student类全限定名").newInstance();　

Student stu = Student.class.newInstance();

3. 使用Constructor类的newInstance方法（反射机制）

class Student {
    private int id;
    
    public Student(Integer id) {
        this.id = id;
    }
}

// 可以调用有参数的和私有的构造函数
Constructor<Student> constructor = Student.class.getConstructor(Integer.class);
       
Student stu = constructor.newInstance(123);

4. 使用Clone方法创建对象

class Student implements Cloneable {

    @Override
    public Object clone() throws CloneNotSupportedException {
        return super.clone();
    }
}

5. 使用(反)序列化机制创建对象

class Student implements Serializable {
   private int id;

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

Student stu = new Student(123);

// 写对象
ObjectOutputStream output = new ObjectOutputStream(new FileOutputStream("student.bin"));
output.writeObject(stu);
output.close();

// 读对象
ObjectInputStream input = new ObjectInputStream(new FileInputStream("student.bin"));
Student stu = (Student) input.readObject();
System.out.println(stu);