blocks|key|2314245|text|您应该创建一个private+static+Player变量，并且在getPlayer()方法中或静态块中创建对象，如果对象为null，则将其赋值给上面的变量。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2314246|public+static+Player+getPlayer(){
++++if(player+==+null){
++++++++player+=+new+Player("name",+p,+i);
++++}
++++return+player;
}|code-block|syntax|javascript|2314247|这样，您只创建一个实例。|2314248|简单的规则，|2314249|类的构造函数应该是private。|ordered-list-item|2314250|将对象保存在private+static变量中。|2314251|为单例对象(没有设置器)创建一个getter。|2314252|您还可以向getter添加synchronized，使其线程安全(可选)。|2314253|entityMap^0|7|L|Y|B|0|0|0|0|9|7|0|6|E|0|0|D|C|0^^$0|@$1|2|3|4|5|6|7|Z|8|@$9|10|A|11|B|C]|$9|12|A|13|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|14|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|15|8|@]|D|@]|E|$]]|$1|M|3|N|5|6|7|16|8|@]|D|@]|E|$]]|$1|O|3|P|5|Q|7|17|8|@$9|18|A|19|B|C]]|D|@]|E|$]]|$1|R|3|S|5|Q|7|1A|8|@$9|1B|A|1C|B|C]]|D|@]|E|$]]|$1|T|3|U|5|Q|7|1D|8|@]|D|@]|E|$]]|$1|V|3|W|5|Q|7|1E|8|@$9|1F|A|1G|B|C]]|D|@]|E|$]]|$1|X|3|-4|5|6|7|1H|8|@]|D|@]|E|$]]]|Y|$]]

You should create a <code>private static Player</code> variable, and in your <code>getPlayer()</code> method or in the static block create the object and assign to the above variable if it's null.

<pre><code>public static Player getPlayer(){
 if(player == null){
 player = new Player("name", p, i);
 }
 return player;
}
</code></pre>

this way you create only a single instance.

<hr>

Simple rules,

<ol>
<li>The constructor of the class should be <code>private</code>.</li>
<li>Keep the object in a <code>private static</code> variable.</li>
<li>Create a getter for the singleton object (no setters).</li>
<li>You can also add <code>synchronized</code> to the getter to make it thread safe (optional).</li>
</ol>

blocks|key|2550829|text|在您调用的另一个类中：Player.getPlayer()|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2550830|它总是返回类的唯一一个静态实例。构造函数是私有的，因此其他类不能通过构造函数初始化类。|2550831|获得Player实例的唯一方法是通过静态方法Player.getPlayer()，因此它是单例的。|2550832|public+class+Player+{

++++String+name;
++++Position+p;
++++Inventory+i;


++++private+static+final+Player+instance+=+new+Player(.....your+argument....);

++++private+Player(String+name,+Position+p,+Inventory+i){

++++}+

++++public+static+Player+getPlayer(){
++++++++return+instance;
++++}

}|code-block|syntax|javascript|2550833|entityMap^0|B|I|0|0|2|6|M|I|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@$9|R|A|S|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|T|8|@]|D|@]|E|$]]|$1|H|3|I|5|6|7|U|8|@$9|V|A|W|B|C]|$9|X|A|Y|B|C]]|D|@]|E|$]]|$1|J|3|K|5|L|7|Z|8|@]|D|@]|E|$M|N]]|$1|O|3|-4|5|6|7|10|8|@]|D|@]|E|$]]]|P|$]]

In another class you call: <code>Player.getPlayer()</code>

It always return the only one static instance of your class. The constructor is private so other class cannot initialize your class via constructor.

The only way to obtain your <code>Player</code> instance is via the static method <code>Player.getPlayer()</code> hence it's singleton.

<pre><code>public class Player {

 String name;
 Position p;
 Inventory i;


 private static final Player instance = new Player(.....your argument....);

 private Player(String name, Position p, Inventory i){

 } 

 public static Player getPlayer(){
 return instance;
 }

}
</code></pre>

blocks|key|2550835|text|只需将私有静态最终INSTANCE字段声明为|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2550836|private+static+final+INSTANCE+=+new+Person(name,+p,+i);|code-block|syntax|javascript|2550837|entityMap^0|9|8|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|P|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|Q|8|@]|D|@]|E|$]]]|L|$]]

Just declare a private static final <code>INSTANCE</code> field as

<pre><code>private static final INSTANCE = new Person(name, p, i);
</code></pre>

blocks|key|1255734|text|基本上，使用这种方法可以隐藏构造函数(private)，并公开获取instance的静态方法。在方法中，检查instance+if+null，如果是，则使用提供的参数对其进行初始化。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1255735|最后，返回instance。|1255736|注意到在这里，如果您不止一次调用getPlayer方法，那么实例将被创建(在进一步调用方法getPlayer时将是相同的)，在第一次调用静态方法时提供的参数将是相同的。|BOLD|1255737|public+class+Player+{

++++String+name;
++++Position+p;
++++Inventory+i;

++++private+static+Player+instance;

++++private+Player(String+name,+Position+p,+Inventory+i){
++++++++//+...
++++}

++++public+static+Player+getPlayer(String+name,+Position+p,+Inventory+i){
++++++++if+(instance+==+null)+{
++++++++++++instance+=+new+Player(name,+p,+i);
++++++++}
++++++++return+instance;
++++}

}|code-block|syntax|javascript|1255738|此外，如果您想正确地使用单例模式，那么在创建实例之后，不应该设置属性(没有setters方法)。|1255739|entityMap^0|J|7|X|8|1I|8|1U|4|0|5|8|0|0|3|G|9|19|9|0|0|0^^$0|@$1|2|3|4|5|6|7|T|8|@$9|U|A|V|B|C]|$9|W|A|X|B|C]|$9|Y|A|Z|B|C]|$9|10|A|11|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|12|8|@$9|13|A|14|B|C]]|D|@]|E|$]]|$1|H|3|I|5|6|7|15|8|@$9|16|A|17|B|J]|$9|18|A|19|B|C]|$9|1A|A|1B|B|C]]|D|@]|E|$]]|$1|K|3|L|5|M|7|1C|8|@]|D|@]|E|$N|O]]|$1|P|3|Q|5|6|7|1D|8|@]|D|@]|E|$]]|$1|R|3|-4|5|6|7|1E|8|@]|D|@]|E|$]]]|S|$]]

Basically, with this approach you hide the constructor (<code>private</code>) and exposes a static method for getting the <code>instance</code>. In the method you check if the <code>instance</code> if <code>null</code>, if so, you initialise it with the provided arguments.

Finally you return the <code>instance</code>.

Notice here if you call the <code>getPlayer</code> method more than once, the instance will be created (and will be the same in further calls of method <code>getPlayer</code>) with the arguments provided the first time the static method was called.

<pre><code>public class Player {

 String name;
 Position p;
 Inventory i;

 private static Player instance;

 private Player(String name, Position p, Inventory i){
 // ...
 }

 public static Player getPlayer(String name, Position p, Inventory i){
 if (instance == null) {
 instance = new Player(name, p, i);
 }
 return instance;
 }

}
</code></pre>

Additionally, if you want to use the singleton pattern properly, you should not set the attributes (no setters methods) once the instance is created.

I recently read about the singleton principle but I dont quite get how I can initialize this single instance of a class form another class if the constructor is <code>private</code>. And how do I set parameters from another class if the constructor is supposed to be <code>private</code>?

<pre><code>public class Player {

 String name;
 Position p;
 Inventory i;

 private Player(String name, Position p, Inventory i){

 }

 static {
 instance = 
 }

 public static Player getPlayer(){
 return instance;
 }

}
</code></pre>

How do I make sure to initialize only one Instance but from another class?

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。

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我最近读到了关于单例原则的文章，但是如果构造函数是private的话，我不太清楚如何初始化一个类的单个实例，形成另一个类。如果构造函数应该是private，那么如何从另一个类中设置参数？public class Player {    String name;    Position p;    Inventory i...

问如何确保只初始化一个实例，而不是从另一个类初始化？
EN

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问如何确保只初始化一个实例，而不是从另一个类初始化？EN