If you inherit from an activity where certain member variables were declared, how do you access these member variables in the subclass executing the inheritance?
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Also check that you don't have a naming conflict: java.sys-con.com/node/46344 if you're running into unexpected behaviorjefflunt– jefflunt2012-01-06 19:26:49 +00:00Commented Jan 6, 2012 at 19:26
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4 Answers
public or protected member names can be accessed via this.memberName from any constructor or non-static method or initializer.
private or package level members (accessed from a subclass in a different package) cannot be accessed directly and will need to be accessed via an unprivileged interface such as a public getter.
Comments
class A {
protected int a = 3;
}
class B extends A {
protected int b = 2;
void doIt() {
System.out.println("super.a:" + super.a);
System.out.println("this.b: " + this.b);
}
}
4 Comments
mre
You don't need the
super keyword.
ollins
That's right. But this is a beginner question. So, I want to make it absolutely clear.
Ted Hopp
You would only need the
super keyword if the field was hidden by a field in the subclass.ollins
Also right :) . But I don't want explain the abbreviations. If user1058210 goes this way, everything will be fine... and at some day he will find the shorter solution.
If the members were declared private, or if they were declared with default (package) access and your subclass is in a different class, you cannot access the variables. If accessors were provided, you can use those. Otherwise, they are not accessible.
If the members were declared protected or public, then you access them as if they were declared in your own class (this.var, or just var if there's no ambiguity). If you have a member in the subclass with the same name as the superclass, you can use super.var to access the superclass variable.
Comments
As stated by others, public and protected fields can be accessed via this.field from the subclass. Package-private fields can also be accessed in the same way, but only if the subclass is in the same package as the parent.
Private fields cannot be accessed in this way, but they can be accessed using Java reflection, if the security settings permit it. It's generally not recommended practice (private members are usually private for a reason), but it can be useful in some situations, for example accessing private class members for code testing purposes. See the answers to this question for how to use reflection in this way.
