blocks|key|2280948|text|您试图使用'this'来引用静态变量，而不是实例变量。'+this+'仅用于引用该类实例化对象的实例变量。您不能使用'this'来引用类中的静态变量。|type|unstyled|depth|inlineStyleRanges|offset|length|style|BOLD|entityRanges|data|2280949|当您使用'+this+'时，您说的是“我想引用这个类的特定实例化的变量”。另一方面，不管实例化如何，静态总是类的相同变量。|2280950|此外，引用实例变量的正确语法是由点运算符：|2280951|this.x+=+42;+//correct
this->x+=+42;+//will+not+compile+as+its+not+valid+Java|code-block|syntax|javascript|2280952|所以从本质上说，你所追求的是如下所示：|2280953|public+class+Foo+{

++++private+int+x;

++++public+void+setX(int+x)+{
++++++++this.x+=+x;
++++}

++++public+int+getX()+{
++++++++return+this.x;
++++}
}

public+class+HelloWorld+{

++++public+static+void+main(String[]+args)
++++{
++++++++Foo+foo+=+new+Foo();
++++++++foo.setX(45);

++++++++System.out.println(foo.getX());
++++}

}|2280954|entityMap^0|5|6|R|8|1M|6|1Y|2|0|4|8|1E|2|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@$9|V|A|W|B|C]|$9|X|A|Y|B|C]|$9|Z|A|10|B|C]|$9|11|A|12|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|13|8|@$9|14|A|15|B|C]|$9|16|A|17|B|C]]|D|@]|E|$]]|$1|H|3|I|5|6|7|18|8|@]|D|@]|E|$]]|$1|J|3|K|5|L|7|19|8|@]|D|@]|E|$M|N]]|$1|O|3|P|5|6|7|1A|8|@]|D|@]|E|$]]|$1|Q|3|R|5|L|7|1B|8|@]|D|@]|E|$M|N]]|$1|S|3|-4|5|6|7|1C|8|@]|D|@]|E|$]]]|T|$]]

You're attempting to use 'this' to refer to a static, not an instance variable. 'this' is only used to refer to the instance variables of an instantiated object of this class. You cannot use 'this' to refer to static variables on a class.

When you use 'this' you are saying "I want to refer to the variables of this particular instantiation of this class". A static on the other hand is always going to be the same variable for the class, irrespective of instantiation.

In addition the correct syntax for referring to an instance variable is by the dot operator:

<pre><code>this.x = 42; //correct
this-&gt;x = 42; //will not compile as its not valid Java
</code></pre>

So essentially what you're after is something like the following:

<pre><code>public class Foo {

 private int x;

 public void setX(int x) {
 this.x = x;
 }

 public int getX() {
 return this.x;
 }
}

public class HelloWorld {

 public static void main(String[] args)
 {
 Foo foo = new Foo();
 foo.setX(45);

 System.out.println(foo.getX());
 }

}
</code></pre>

blocks|key|2300619|text|Java有this作为前缀，但它是对当前实例的引用。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2300620|静态方法和属性与类相关联，而不是实例，因此不能在静态方法中使用this。|2300621|public+class+HelloWorld+{

++++public+int+x+=+0;+//+note:+now+it's+an+instance+attribute

++++public+static+void+main(String[]+args)+{

++++++++HelloWorld+hw+=+new+HelloWorld();


++++++++System.out.println(hw.x);
++++}

++++public+int+getX()+{+return+this.x;+}
++++public+void+setX(int+x)+{+this.x+=+x;+}
}|code-block|syntax|javascript|2300622|entityMap^0|5|4|0|V|4|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|R|8|@$9|S|A|T|B|C]]|D|@]|E|$]]|$1|H|3|I|5|J|7|U|8|@]|D|@]|E|$K|L]]|$1|M|3|-4|5|6|7|V|8|@]|D|@]|E|$]]]|N|$]]

Java has <code>this</code> as a prefix, but it's a reference to the current instance.

Static methods and attributes are associated with a class, not an instance, so you can't use <code>this</code> inside a static method.

<pre><code>public class HelloWorld {

 public int x = 0; // note: now it's an instance attribute

 public static void main(String[] args) {

 HelloWorld hw = new HelloWorld();


 System.out.println(hw.x);
 }

 public int getX() { return this.x; }
 public void setX(int x) { this.x = x; }
}
</code></pre>

blocks|key|635259|text|您只能在对象实例中使用“此”。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|635260|“静态”，顾名思义，是在任何物体之外。|635261|在Java文档中有一个很好的链接：|635262|http://download.oracle.com/javase/tutorial/java/javaOO/classvars.html|offset|length|635263|“希望能帮上忙！|635264|entityMap|0|LINK|mutability|MUTABLE|url^0|0|0|0|0|1X|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|T|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|U|8|@]|9|@]|A|$]]|$1|F|3|G|5|6|7|V|8|@]|9|@$H|W|I|X|1|Y]]|A|$]]|$1|J|3|K|5|6|7|Z|8|@]|9|@]|A|$]]|$1|L|3|-4|5|6|7|10|8|@]|9|@]|A|$]]]|M|$N|$5|O|P|Q|A|$R|G]]]]

You can only use "this" from within an object instance.

"static", by definition, is OUTSIDE of ANY object.

Here's an excellent link in the Java documentation:

<a href="http://download.oracle.com/javase/tutorial/java/javaOO/classvars.html" rel="nofollow">http://download.oracle.com/javase/tutorial/java/javaOO/classvars.html</a>

'Hope that helps!

blocks|key|2280986|text|对于静态变量，请使用ClassName+(就像您所做的那样)。例如(非静态)变量，请使用this.variableName。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2280987|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

for static variables, use ClassName (like you did). For instance (non-static) variables, use this.variableName

blocks|key|633570|text|您可以使用它来访问实例变量和方法，因为您正在使用this访问静态变量，因此会得到此错误。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|633571|还有..。java没有=>，在java中使用.|633572|++objectName.variableName+=+newValue|code-block|syntax|javascript|633573|entityMap^0|O|4|0|B|2|M|1|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|R|8|@$9|S|A|T|B|C]|$9|U|A|V|B|C]]|D|@]|E|$]]|$1|H|3|I|5|J|7|W|8|@]|D|@]|E|$K|L]]|$1|M|3|-4|5|6|7|X|8|@]|D|@]|E|$]]]|N|$]]

you can use it to access instance variables and methods, you are getting this error because you are using <code>this</code> to access static variables.

and also ... java doesn't have <code>=&gt;</code>, in java you use the <code>.</code> 

<pre><code> objectName.variableName = newValue
</code></pre>

blocks|key|2281045|text|从变量中删除static修饰符，然后使用this尝试它。以下是不同之处：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2281046|静态变量在整个程序中只存在一次。无论您身在何处，您都可以参考HelloWorld.x，而且它总是一样的。这意味着，正如您声明的那样，任何人也可以修改它，这可能是一件好事，也可能不是好事。|2281047|成员变量(不是静态声明)是类实例的本地变量，这意味着您必须使用new创建实例才能使用它。但是，每次使用new创建该类的新实例时，其非静态字段都会有所不同。这就是为什么您必须使用this，或者，如果是在不同的类中，则使用对特定实例的引用来访问它们。|2281048|entityMap^0|6|6|K|4|0|U|C|0|V|3|1F|3|2G|4|0^^$0|@$1|2|3|4|5|6|7|L|8|@$9|M|A|N|B|C]|$9|O|A|P|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|Q|8|@$9|R|A|S|B|C]]|D|@]|E|$]]|$1|H|3|I|5|6|7|T|8|@$9|U|A|V|B|C]|$9|W|A|X|B|C]|$9|Y|A|Z|B|C]]|D|@]|E|$]]|$1|J|3|-4|5|6|7|10|8|@]|D|@]|E|$]]]|K|$]]

Remove the <code>static</code> modifier from your variable and then try it with <code>this</code>. Here is the difference:

Static variables exist only once in the whole program. No matter where you are, you could refer to <code>HelloWorld.x</code> and it would always be the same thing. That means, as you've declared it, anyone can modify it too, which may or may not be a good thing.

Member variables (not declared with static) are local to an instance of a class, which means you have to have created an instance with <code>new</code> before you can use it. However, every time you use <code>new</code> to create a new instance of that class, its non-static fields will be different. That is why you have to use <code>this</code> or, if in a different class, a reference to a specific instance in order to access them.

blocks|key|2281068|text|用于getter/setters/constructors。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2281069|例如。|2281070|class+Test+{

int+x;
int+y;

public+void+Test(int+x,+int+y)+{
++this.x=x;
++this.y=y;
}

public+void+setX(int+x)+{
++this.x=x;
}
}|code-block|syntax|javascript|2281071|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|L|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|M|8|@]|9|@]|A|$G|H]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

Use this for getters/setters/constructors.

For example.

<pre><code>class Test {

int x;
int y;

public void Test(int x, int y) {
 this.x=x;
 this.y=y;
}

public void setX(int x) {
 this.x=x;
}
}
</code></pre>

blocks|key|635342|text|澄清：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|635343|在getter方法中，没有必要使用关键字this+(如其他答案所示)。如果您是Java新手，这将向您介绍变量作用域(局部变量与实例变量)。换句话说，以下内容工作得很好：|offset|length|style|CODE|635344|public+class+Foo+{
++++private+int+x;

++++public+void+setX(int+x)+{
++++++++this.x+=+x;+//Here+the+keywork+this+is+necessary!
++++}

++++public+int+getX()+{
+++++++++return+x;+//in+this+case+the+'x'+can+only+be+instance+variable+
++++}
}|code-block|syntax|javascript|635345|在调用同一个类中定义的构造函数时，this还有另一个重要用途(您可能也希望检查关键字'super‘)。检查以下内容：|635346|public+class+HelloWorld+{
++++public+static+void+main(String[]+args)+{

++++++++Foo+foo1+=+new+Foo();
++++++++Foo+foo2+=+new+Foo(3,+4,+5);

++++++++System.out.println("Foo1:\n"+%2B+foo1);
++++++++System.out.println("Foo2:\n"+%2B+foo2);
++++}
}

class+Foo+{
++++private+int+x,+y,+z;

++++public+Foo()+{
++++++++this(-1,+-1);
++++}

++++public+Foo(int+x,+int+y)+{
++++++++this.x+=+x;
++++++++this.y+=+y;
++++}

++++public+Foo(int+x,+int+y,+int+z)+{
++++++++this(x,+y);
++++++++this.z+=+z;
++++}

++++@Override
++++public+String+toString()+{
++++++++return+"x=+"+%2B+x+%2B+"\ny=+"+%2B+y+%2B+"\nz=+"+%2B+z+%2B+"\n";
++++}
}|635347|享受吧！|635348|entityMap^0|0|K|4|0|0|H|4|0|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|V|8|@$D|W|E|X|F|G]]|9|@]|A|$]]|$1|H|3|I|5|J|7|Y|8|@]|9|@]|A|$K|L]]|$1|M|3|N|5|6|7|Z|8|@$D|10|E|11|F|G]]|9|@]|A|$]]|$1|O|3|P|5|J|7|12|8|@]|9|@]|A|$K|L]]|$1|Q|3|R|5|6|7|13|8|@]|9|@]|A|$]]|$1|S|3|-4|5|6|7|14|8|@]|9|@]|A|$]]]|T|$]]

A clarification:

in getter methods it's not necessary to use the keyword <code>this</code> (as it's been shown in other answers). If you're new to Java this will introduce you to variable scopes (local variables vs instance variables). In other words the following works perfectly:

<pre><code>public class Foo {
 private int x;

 public void setX(int x) {
 this.x = x; //Here the keywork this is necessary!
 }

 public int getX() {
 return x; //in this case the 'x' can only be instance variable 
 }
}
</code></pre>

There is also another important use of <code>this</code> for invoking constructors defined in the same class (You might want to check the keyword 'super' as well). Check the following:

<pre><code>public class HelloWorld {
 public static void main(String[] args) {

 Foo foo1 = new Foo();
 Foo foo2 = new Foo(3, 4, 5);

 System.out.println("Foo1:\n" + foo1);
 System.out.println("Foo2:\n" + foo2);
 }
}

class Foo {
 private int x, y, z;

 public Foo() {
 this(-1, -1);
 }

 public Foo(int x, int y) {
 this.x = x;
 this.y = y;
 }

 public Foo(int x, int y, int z) {
 this(x, y);
 this.z = z;
 }

 @Override
 public String toString() {
 return "x= " + x + "\ny= " + y + "\nz= " + z + "\n";
 }
}
</code></pre>

Enjoy!

Does the <code>this</code> prefix for accessing member variables exist in Java? 

Here is my HelloWorld code:

<pre><code>public class HelloWorld {

 public static int x = 0;

 public static void main(String[] args) {

 HelloWorld.x = 45;

 System.out.println(HelloWorld.x);
 }
}
</code></pre>

The above code works with/without the class name prefixing the variable <code>x</code>. However, if i try: <code>this.x = 45;</code> or <code>this-&gt;x = 45;</code> I receive an error:

<blockquote>
 non-static variable this cannot be referenced from a static context
</blockquote>

I understand member variables can be accessed without the <code>HelloWorld</code> (class name) prefix, like I have done. But, I want to know if the this prefix exists in Java, how do I use it?

EDIT:

Also, could you provide an example where <code>this</code> is appropriate? 

duffymo &amp; byte - I greatly appreciate your help. Thanks.

'this' prefix in Java?

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

文章

问答

视频

学习中心

腾讯云实验室

直播

竞赛

腾讯云代码分析专区

腾讯iOA零信任安全管理系统专区

腾讯云架构师技术同盟交流圈

腾讯云数据库专区

腾讯云顾问专区

腾讯云原生专区

腾讯混元专区

腾讯云TCE专区

腾讯云Lighthouse专区

腾讯云HAI专区

腾讯云Edgeone专区

腾讯云存储专区

腾讯云智能专区

腾讯轻联专区 

腾讯云开发专区

TAPD专区

腾讯轻量云游戏服专区

腾讯云最具价值专家

腾讯云架构师技术同盟

腾讯云创作之星

腾讯云开发者先锋

腾讯云代码助手

云原生构建

TAPD 敏捷项目管理

Cloud Studio

SDK中心

API中心

命令行工具

涵盖代码开发、场景应用、自动测试全流程，助你从零构建专属AI助手

一站式MCP教程库，解锁AI应用新玩法

在Java中是否存在访问成员变量的this前缀？以下是我的HelloWorld代码：public class HelloWorld {    public static int x = 0;    public static void main(String[] args) {        HelloWorld.x ...

问这是Java的前缀吗？
EN

Stack Overflow用户

社区

活动

圈层

关于

腾讯云开发者

热门产品

热门推荐

更多推荐

问这是Java的前缀吗？EN