我以为内部类可以访问外部类变量/方法? [英] I thought inner classes could access the outer class variables/methods?
问题描述
我确实阅读了许多讨论内部类的主题,我的印象是内部类可以访问封闭类的变量和方法。在下面我有一个外部类和一个内部类,在测试类中我创建了一个外部类的实例,然后从中创建了一个内部类的实例。但是我无法通过内部类引用访问String变量a。救命?
I did read a number of topics discussing inner classes, and i was under the impression that an inner class has access to the variables and methods of the enclosing class. In the following i have an outer class and an inner class, in the test class i create an instance of the outer class and then from that i create an instance of the inner class. However i am not able to access the String variable a through the inner class reference. Help?
public class OuterClass {
String a = "A";
String b = "B";
String c = "C";
class InnerClass {
int x;
}
public static class StaticInnerClass {
int x;
}
public String stringConCat() {
return a + b + c;
}
}
public class TestStatic {
public static void main(String args[]) {
OuterClass.StaticInnerClass staticClass = new OuterClass.StaticInnerClass();
OuterClass outer = new OuterClass();
OuterClass.InnerClass inner = outer.new InnerClass();
System.out.println(inner.a);// error here, why can't i access the string
// variable a here?
}
}
推荐答案
内部类可以通过自己的方法访问外部类方法和属性。请查看以下代码:
The inner class can access the outer class methods and properties through its own methods. Look at the following code:
class OuterClass {
String a = "A";
String b = "B";
String c = "C";
class InnerClass{
int x;
public String getA(){
return a; // access the variable a from outer class
}
}
public static class StaticInnerClass{
int x;
}
public String stringConCat(){
return a + b + c;
}
}
public class Test{
public static void main(String args[]) {
OuterClass.StaticInnerClass staticClass = new OuterClass.StaticInnerClass();
OuterClass outer = new OuterClass();
OuterClass.InnerClass inner = outer.new InnerClass();
System.out.println(inner.getA()); // This will print "A"
}
}
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