英文:
',' expected instead of ';' on Reference Declaration in JAVA
问题
这是类，错误出现在 `flyBehavir` 声明上，就在分号上面：
```java
package simUduck;
public class duck {
void display(){
}
Fly flyBehaviour; // 这里
flyBehaviour = new Fly(); // 这里
}
这是 Fly 类：
package simUduck;
public class Fly {
void fly(){
}
}
我实际上不想在 duck 类中初始化它，我只想在那里引用它，子类会初始化它。任何帮助将不胜感激。
以下语句不会产生错误：
Fly flybehavior = new Fly();
<details>
<summary>英文:</summary>
*Here is the class and the error is on `flyBehavir` declaration, right on the semicolon*
```java
package simUduck;
public class duck {
void display(){
}
Fly flyBehaviour;
flyBehaviour = new Fly();
}
Here is the Fly class
package simUduck;
public class Fly {
void fly(){
}
}
I don't actually want a initialization in duck class, I just want a reference there and the child classes will initialize it. Any help would be appreciated.
The following statement doesn't give any error
Fly flybehavior = new Fly();
答案1
得分: 3
flyBehaviour = new Fly(); 是一个位于方法外部的语句。这是不允许的。每个语句必须位于方法、构造函数或初始化块内部。
因此，要么将其重写为初始化块（正如您在最后一行中所示），要么将其放入构造函数中：
public Duck() {
flyBehaviour = new Fly();
}
（还要注意，我将 Duck 的首字母大写，因为按照惯例在 Java 中所有类名都应该大写）。
英文:
flyBehaviour = new Fly(); is a statement outside of a method. That is not allowed. Each statement must be inside a method, constructor or initializer block.
So either rewrite it as an initializer (as you showed in your last line) or put it into a constructor:
public Duck() {
flyBehaviour = new Fly();
}
(Also note, that I capitalized Duck, because by convention all classes should be upper-case in Java).
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