从不同的 JAVA 包调用方法
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calling methods from different package JAVA
提问by reddit_10
I have two packages; pack1 and pack2. in pack1 I have two classes the main called Prog and another one called ClassA. In pack2 I have one class called ClassB.
我有两个包裹；包1和包2。在 pack1 中，我有两个类，主要称为 Prog，另一个类称为 ClassA。在 pack2 中，我有一个名为 ClassB 的类。
I am trying to understand why I can't call a method from ClassB using the object. I can do that using the main class but not with another class.
我试图理解为什么我不能使用对象从 ClassB 调用方法。我可以使用主类来做到这一点，但不能使用另一个类。
Here's the code:
这是代码：
package pack1;
import pack2.ClassB;
public class Prog {
public static void main(String[] args){
}
}
Code for ClassA
A 类代码
package pack1;
import pack2.ClassB;
public class ClassA {
ClassB o3 = new ClassB();
// Error won't compile
System.out.println(o3.getText());
}
Code for ClassB:
B类代码：
package pack2;
public class ClassB {
final String TEXT = "This is a text";
public String getText(){
return TEXT;
}
}
回答by Paul
The problem here isn't that you can't access the method. The problem is that statements must be enclosed either in a constructor, amethod-declaration or an initializer-block. So this would be valid code for example:
这里的问题不在于您无法访问该方法。问题是语句必须包含在构造函数、方法声明或初始化程序块中。所以这将是有效的代码，例如：
enter codepackage pack1;
import pack2.ClassB;
public class ClassA {
ClassB o3 = new ClassB();
public void someMethod(){
System.out.println(o3.getText());
}
}
