java类只读怎么办_如何在Java中制作一个只读类？

java类只读怎么办

The question is that "can we make a read-only class in Java?"

问题是“我们可以用Java制作一个只读类吗？”

The answer is: "Yes, we can make a read-only in java."

答案是： “是的，我们可以在Java中将其设为只读。”

在Java中定义只读类 (Defining read-only class in Java)

Now, we will see in few steps, how to make Read-only class and the various steps in given below:

现在，我们将在几个步骤中看到如何制作只读类以及下面给出的各个步骤：

We can make a class read-only by making all of the data members private.

我们可以通过将所有数据成员设为私有来将类设为只读。

Please note:

请注意：

If we make a class read-only, then we can’t modify the properties or data members value of the class.
如果我们将类设为只读，则无法修改该类的属性或数据成员值。
If we make a class read-only, then we can only read the properties or data members value of the class.
如果我们将类设为只读，则只能读取该类的属性或数据成员值。
The read-only class will contain only getter methods which return the value of the private properties to the main() function.
只读类将仅包含将私有属性的值返回给main()函数的getter方法。
The read-only class can contain setter methods if we want to modify the value of the private properties after reading because there is our choice to keep setter method in the class but as per based on the concepts we should not contain.
如果我们想在读取后修改私有属性的值，则只读类可以包含setter方法，因为可以选择将setter方法保留在类中，但是根据我们不应该包含的概念。

Now, we will see the objective of the getter method, why it is required?

现在，我们将看到getter方法的目标，为什么需要它？

Few points need to remember about getter methods are given below:

以下是关于getter方法需要记住的几点：

As we know that "private" data member of the class is accessible in the same class only.
众所周知，该类的“私有”数据成员只能在同一类中访问。
Let suppose we want to access "private" data member of the class in outside class. So, in that case, we need to declare public "getter" methods.
假设我们要在外部类中访问该类的“私有”数据成员。因此，在这种情况下，我们需要声明公共的“ getter”方法。
The objective of the getter method is used to view the private variable values.
getter方法的目标用于查看私有变量值。

Syntax:

句法：

    public returntype getDataMember_Name();

In the Getter method, it is not mandatory the same data member name after get, but it is convenient for our understanding that we should consider the same name as the data member after get.

在Getter方法中，获取后并不一定要使用相同的数据成员名称，但是对于我们理解而言，方便的是，我们应该考虑与获取后的数据成员使用相同的名称。

There are few advantages of getter methods are given below:

下面给出了getter方法的一些优点：

Hiding the internal representation of the private data member.
隐藏私有数据成员的内部表示。
Getter methods provide access level hierarchy.
Getter方法提供访问级别层次结构。
This method adds additional functionality easily later.
此方法以后可以轻松添加其他功能。
This class allows getter methods to be passed around as lambda expressions rather than values.
此类允许getter方法作为lambda表达式而不是值传递。
The private data member is accessible from outside the class with the help of getter methods.
可以使用getter方法从类外部访问私有数据成员。

Example:

例：

// Java program to demonstrate the example of 
// making Read-only class in Java
public class Weeks {
// Private Data Member Declaration
private String days = "7 days";
// Defining Getter method to return the value of
// private properties.
public String getDays() {
return days;
}
public static void main(String[] args) {
// Weeks object instanstiation
Weeks w = new Weeks();
// Get the value of the private member
String result = w.getDays();
// Display the value of the private properties
System.out.println("Days in a Week:" + " " + result);
}
}

Output

输出量