JAVA
public class A {
string amountA;
B b;
}
public class B {
string amountB;
public void setValue(String value) {
amountB = value;
Also, I need to set amountA = value;. Is it possible? See main method
}
}
... main(String... args) {
A a = new A();
B b = a.getB(); // b is a member of A
b.setValue("25") // this should also change 'amountA' in object 'a' to '25'
}
If you need to set both valueA and ValueB to the same value, it makes more sense to have a setter in class A that would set both of them :
public void setValue(String value) {
amountA = value;
b.setValue(value);
}
You can't access an instance of A from within an instance of B, since B is not an inner class of A. You can create an instance of B that is not related at all to any instance of A.
public class A {
public class B {
string amountB;
public void setValue(String value) {
amountB = value;
amountA = value; // Using A.this.amountA
}
}
string amountA;
public B createB() {
return new B(); // Provides A.this to the B instance.
}
}
... main(String... args) {
A a = new A();
B b = a.createB(); // b is created inside A
b.setValue("25") // this should also change 'amountA' in object 'a' to '25'
}
You can use an inner class.
The class itself should better create the instance, so that A.this is set into the b.
Alternatively
B b = a.new B();
But I never ever used that.
Inner classes are practical for a container element having access to its container class.
Another solution is to make a method in A with the B object as parameter or so.
It sounds like you want to have A derive from B rather than contain an instance of B. That way the valueA in an instance of A and the valueA in the instance of B associated with that instance of A are really the same variable. You can also have data in A that isn't shared with B by declaring it in A. For example,
public class A extends B {
public String amountAonly; // a string in A that's not in B
public B getB() { return (B)this; } // typecast to treat A like B
}
public class B {
public String amountA; // a string that's in both A and B
public void setValue(String value) {
amountA = value;
}
}
...
main(String[] args) {
A a = new A();
B b = a.getB(); // b is the B associated with a
b.setValue("25"); // will also change 'amountA' in object 'a' to '25'
}
