blocks|key|440278|text|出于encapsulation的考虑，您应该始终使用第二种方法。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|440279|myLocalVar+=+myClass.getMyVarVal();|code-block|syntax|javascript|440280|效率方面，你很可能不会注意到不同之处。|440281|entityMap|0|LINK|mutability|MUTABLE|url|http://en.wikipedia.org/wiki/Encapsulation_%2528object-oriented_programming%2529^0|2|D|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@$A|T|B|U|1|V]]|C|$]]|$1|D|3|E|5|F|7|W|8|@]|9|@]|C|$G|H]]|$1|I|3|J|5|6|7|X|8|@]|9|@]|C|$]]|$1|K|3|-4|5|6|7|Y|8|@]|9|@]|C|$]]]|L|$M|$5|N|O|P|C|$Q|R]]]]

For the sake of <a href="http://en.wikipedia.org/wiki/Encapsulation_%28object-oriented_programming%29" rel="noreferrer">encapsulation</a> you should always go with the second alternative.

<pre><code>myLocalVar = myClass.getMyVarVal();
</code></pre>

Efficiency wise you most likely won't notice a difference.

blocks|key|654811|text|一定要使用getter和setter来访问你的属性！|type|unstyled|depth|inlineStyleRanges|entityRanges|data|654812|您还应该看看this。|offset|length|654813|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/questions/1568091/why-use-getters-and-setters^0|0|6|4|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|O|8|@]|9|@$D|P|E|Q|1|R]]|A|$]]|$1|F|3|-4|5|6|7|S|8|@]|9|@]|A|$]]]|G|$H|$5|I|J|K|A|$L|M]]]]

Do ALWAYS use getter and setter to access your properties!

You should also take a look at <a href="https://stackoverflow.com/questions/1568091/why-use-getters-and-setters">this</a>.

blocks|key|440486|text|myClass.getMyVarVal()比较慢，因为它是一个方法调用，所以它在堆栈上创建返回值的入口，等等。但使用getters是更好的OOP实践。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|440487|entityMap^0|0|L|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|K|8|@]|D|@]|E|$]]]|G|$]]

<code>myClass.getMyVarVal()</code> is slower since it is a method call and so it creates entrance on the stack for return value, etc. But it is better OOP practice to use getters.

blocks|key|440541|text|myLocalVar+=+myClass.getMyVarVal();|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|440542|如果您使用的是OOP+concept，那么使用它会很好|unstyled|offset|length|style|CODE|440543|entityMap^0|0|7|3|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|F|7|N|8|@$G|O|H|P|I|J]]|9|@]|A|$]]|$1|K|3|-4|5|F|7|Q|8|@]|9|@]|A|$]]]|L|$]]

<pre><code>myLocalVar = myClass.getMyVarVal();
</code></pre>

it will be good to use it if you are working with <code>OOP</code> concept

blocks|key|655132|text|这两种技术都很糟糕，但使用getter是一种常见的(也是更安全的)实践。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|655133|为了访问公共数据成员(又称公共字段或公共属性)，您必须知道类的实现细节(数据成员名称和数据成员类型)。这是一件坏事；它打破了OOP的“信息隐藏”概念，增加了“耦合性”。|655134|使用getter也很糟糕(就像在糟糕的OOP实践中一样)，因为对象不仅仅是数据的包装器；对象应该封装功能和数据。“将此值存储在此处，以便稍后获取”不是功能，而是hoot功能(就像笼子里的猴子在叫)。不过，在java+(以及其他面向对象的轻量级语言，如c%2B%2B和c#)中，Getters是一种公认的实践。|655135|为了避免你认为我是最纯粹的象牙塔，我当然会使用getter；我使用java，所以我使用getter。|655136|Getters可以很好地完成工作(不是双关语)，只是不要相信"I+R+gud+OOP+Prgmr"，因为如果你使用getter，你就不是一个“好的oop程序员”，你只是一个完成工作的程序员。|655137|编辑:也许是一种更好的方式。|655138|更好的方法是不使用better，而是设计您的类，以便它们公开功能而不是数据。在实践中，这是有问题的；例如，如果您需要在JSP页面上显示一个地址，您可以在请求(或会话或诸如此类)中放置一个具有该地址的bean，并使用getter公开这些值。一种“更纯粹的oop”方法是放置一个公开了“在jsp上显示地址”功能的bean。|655139|Edit2:也许是一个更好的例子。|655140|假设我在美国的一家电话公司工作，我有一个表示客户电话号码的对象。这可能如下所示：|655141|public+class+CustomerPhoneNumber
{
++private+String+npa;+//+numbering+plan+area+(google+search+nanp+for+more+details)
++private+String+nxx;+//+exchange.
++private+String+serviceNumber;

++public+String+toString()
++{
++++return+"("+%2B+npa+%2B+")+"+%2B+nxx+%2B+"-"+%2B+serviceNumber;
++}

++public+boolean+equals(Object+object)
++{
++++...+standard+equals+implementation+(assume+this+works)
++}
}|code-block|syntax|javascript|655142|现在，假设我从表单String+inputPhoneNumber的网页中获得了一个电话号码作为输入。为了便于讨论，接收此输入的类称为“servlet”。|offset|length|style|CODE|655143|我如何回答这个问题：“输入的电话号码是否在我的CustomerPhoneNumber对象列表中？”|655144|选项1是使npa、nxx和serviceNumber数据成员公开并访问它们。这太可怕了。|655145|选项2是为npa、nxx和服务编号提供getter，并将它们与输入进行比较。同样可怕的是，太多的内部细节暴露了出来。|655146|选项3是提供一个返回格式化电话号码的getter+(我在上面调用了这个toString()+)。这更聪明，但仍然很糟糕，因为servlet必须知道getter将使用的格式，并确保以相同的方式格式化输入。|655147|选项4(我称之为"Welcome+to+OOP")提供了一个方法，该方法接受一个字符串，如果字符串与客户服务编号匹配，则返回true。这样更好，可能看起来像这样(名称很长，但对于本例来说已经足够了)：|655148|public+boolean+doesPhoneNumberMatchThisInput(final+String+input)
{
+++String+formattedInput;
+++String+formattedCustomerPhoneNumber+=+npa+%2B+nxx+%2B+serviceNumber;

+++formattedInput+=+...+strip+all+non-digits+from+input.

+++return+StringUtils.equals(formattedCustomerPhoneNumber,+formattedInput);
}|655149|这是赢家，因为没有公开任何实现细节。此外，toString还可用于在JSP页面上输出电话号码。|655150|StringUtils是Apache+Commons+Lang的一部分。|655151|entityMap|0|LINK|mutability|MUTABLE|url|http://commons.apache.org/lang/api-2.6/index.html^0|0|0|0|0|0|0|0|0|0|0|9|N|0|0|0|0|0|0|0|0|C|J|0|0^^$0|@$1|2|3|4|5|6|7|1Q|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|1R|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|1S|8|@]|9|@]|A|$]]|$1|F|3|G|5|6|7|1T|8|@]|9|@]|A|$]]|$1|H|3|I|5|6|7|1U|8|@]|9|@]|A|$]]|$1|J|3|K|5|6|7|1V|8|@]|9|@]|A|$]]|$1|L|3|M|5|6|7|1W|8|@]|9|@]|A|$]]|$1|N|3|O|5|6|7|1X|8|@]|9|@]|A|$]]|$1|P|3|Q|5|6|7|1Y|8|@]|9|@]|A|$]]|$1|R|3|S|5|T|7|1Z|8|@]|9|@]|A|$U|V]]|$1|W|3|X|5|6|7|20|8|@$Y|21|Z|22|10|11]]|9|@]|A|$]]|$1|12|3|13|5|6|7|23|8|@]|9|@]|A|$]]|$1|14|3|15|5|6|7|24|8|@]|9|@]|A|$]]|$1|16|3|17|5|6|7|25|8|@]|9|@]|A|$]]|$1|18|3|19|5|6|7|26|8|@]|9|@]|A|$]]|$1|1A|3|1B|5|6|7|27|8|@]|9|@]|A|$]]|$1|1C|3|1D|5|T|7|28|8|@]|9|@]|A|$U|V]]|$1|1E|3|1F|5|6|7|29|8|@]|9|@]|A|$]]|$1|1G|3|1H|5|6|7|2A|8|@]|9|@$Y|2B|Z|2C|1|2D]]|A|$]]|$1|1I|3|-4|5|6|7|2E|8|@]|9|@]|A|$]]]|1J|$1K|$5|1L|1M|1N|A|$1O|1P]]]]

Both techniques are terrible, but using the getter is the common (and safer) practice.

In order to access a public data member (a.k.a. public field or public property) of a class, you must know the implementation details of the class (the data member name and the data member type). This is a bad thing; it breaks the OOP concept "information hiding" and increases "coupling".

Using a getter is also bad (as in a bad OOP practice) because objects are not just wrappers around data; objects are supposed to encapsulate functionality and data. "store this here value so I can get it later" is not functionality; it is hoot functionality (as in a monkey in a cage hooting). Getters are; however, an accepted practice in java (and other OOP-lite languages like c++ and c#).

Lest you think I am some ivory tower purest, of course I use getters; I use java, so I use getters.

Getters are fine for getting the work done (no pun), just don't walk around believing that "I R gud OOP Prgmr", because if you use getters you are not a "good oop programmer", you are just a programmer who gets work done.

Edit: Perhaps a better way.

The better way is to not use getters, but to instead design your classes so they expose functionality not data. In practice, there is a point where this breaks down; for example, if you need to display an address on a JSP page, you put a bean in the request (or session or blah) with the address and expose the values using getters. A "more oop pure" way would be to put a bean that exposed "display the address on a jsp" functionality.

Edit2: Perhaps a better example.

Say I work for a phone company, in the USA, and I have an object that represents a customers phone number. This might look like the following:

<pre><code>public class CustomerPhoneNumber
{
 private String npa; // numbering plan area (google search nanp for more details)
 private String nxx; // exchange.
 private String serviceNumber;

 public String toString()
 {
 return "(" + npa + ") " + nxx + "-" + serviceNumber;
 }

 public boolean equals(Object object)
 {
 ... standard equals implementation (assume this works)
 }
}
</code></pre>

Now say I get a phone number as an input from a web page in the form <code>String inputPhoneNumber</code>. For the purposes of discussion, the class that receives this input is called "the servlet".

How can I answer this question: "Is the input phone number in my list of CustomerPhoneNumber objects?"

Option 1 is make the npa, nxx, and serviceNumber data members public and access them. This is terrible.

Option 2 is provide getters for npa, nxx, and service number and compare them with the input. Also terrible, too many internal details exposed.

Option 3 is provide a getter that returns the formatted phone number (I called this toString() above). This is smarter but still terrible because the servlet has to know the format that will be used by the getter and ensure that the input is formatted the same way.

Option 4 (I call this "Welcome to OOP") provide a method that takes a String and returns true if that matches the customer service number. This is better and might look like this (the name is long, but sufficient for this example):

<pre><code>public boolean doesPhoneNumberMatchThisInput(final String input)
{
 String formattedInput;
 String formattedCustomerPhoneNumber = npa + nxx + serviceNumber;

 formattedInput = ... strip all non-digits from input.

 return StringUtils.equals(formattedCustomerPhoneNumber, formattedInput);
}
</code></pre>

This is the winner because no implementation details are exposed. Also the toString can be used to output the phone number on a JSP page.

StringUtils is part of <a href="http://commons.apache.org/lang/api-2.6/index.html" rel="noreferrer">Apache Commons Lang</a>.

blocks|key|655198|text|只需创建对象并使用object.variablename;或object.methodName();即可使非静态reference...no使用getter是必需的。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|655199|entityMap^0|9|K|U|K|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]|$9|K|A|L|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|M|8|@]|D|@]|E|$]]]|G|$]]

Just create object and <code>object.variablename;</code> or <code>object.methodName();</code> can be used to make non-static reference...no use of getter is required.

I can call variables 2 ways.

One is just to do it like this:

<pre><code>MyClass myClass = new MyClass(); 

myLocalVar = myClass.myVarVal;
</code></pre>

And the other way is to use a getter like this:

<pre><code>myLocalVar = myClass.getMyVarVal();
</code></pre>

Both ways are working fine, but I was wondering what would be the most efficient/proper way of doing this?

Thanks

Proper way of getting variable from another class

我可以用两种方式调用变量。一种是像这样做：MyClass myClass = new MyClass();    myLocalVar = myClass.myVarVal;另一种方法是使用这样的getter：myLocalVar = myClass.getMyVarVal();这两种方法都工作得很好，但我想知道做这件...

问从另一个类获取变量的正确方法
EN

社区

活动

资源

关于

腾讯云开发者

热门产品

热门推荐

更多推荐

问从另一个类获取变量的正确方法EN

社区

活动

资源

关于

腾讯云开发者

热门产品

热门推荐

更多推荐

问从另一个类获取变量的正确方法
EN