How to Design the Following Data Structure in Java
I have a list, L1<A>, of about 60 to 120 objects, A, that themselves contain a list L2<D> of objects, D.
The L2<D>s are identical for all A.
The user can upload new Ds, and every time the program has to go through all of L1 and add add the new D to each L2. Obviously, I would rather have a master L2 that can just be updated once and have every A refer to that list, but I don't want to make some kind of global variable L2.
If I make a single instance of L2, do I just have to pass L2 to every A in L1, or can I get each A to refer to the single L2 without using a global variable?
java data-structures global-variables
asked Nov 15 '18 at 0:45
user2303321user2303321
9219
add a comment |
I have a list, L1<A>, of about 60 to 120 objects, A, that themselves contain a list L2<D> of objects, D.
The L2<D>s are identical for all A.
The user can upload new Ds, and every time the program has to go through all of L1 and add add the new D to each L2. Obviously, I would rather have a master L2 that can just be updated once and have every A refer to that list, but I don't want to make some kind of global variable L2.
If I make a single instance of L2, do I just have to pass L2 to every A in L1, or can I get each A to refer to the single L2 without using a global variable?
java data-structures global-variables
asked Nov 15 '18 at 0:45
user2303321user2303321
9219
Passing around a shared instance is not the same as a global variable, and seems like a perfectly appropriate solution.
– shmosel
Nov 15 '18 at 0:48
Sounds like you should pass the one L2 to every A as a constructor argument, but I can't be sure since you've omitted any information about what these things actually mean. The next time you ask a question like this, don't try to turn it into something so generic -- not all similar questions have the same answer.
– Matt Timmermans
Nov 15 '18 at 4:45
add a comment |
I have a list, L1<A>, of about 60 to 120 objects, A, that themselves contain a list L2<D> of objects, D.
The L2<D>s are identical for all A.
The user can upload new Ds, and every time the program has to go through all of L1 and add add the new D to each L2. Obviously, I would rather have a master L2 that can just be updated once and have every A refer to that list, but I don't want to make some kind of global variable L2.
If I make a single instance of L2, do I just have to pass L2 to every A in L1, or can I get each A to refer to the single L2 without using a global variable?
java data-structures global-variables
asked Nov 15 '18 at 0:45
user2303321user2303321
9219
I have a list, L1<A>, of about 60 to 120 objects, A, that themselves contain a list L2<D> of objects, D.
The L2<D>s are identical for all A.
The user can upload new Ds, and every time the program has to go through all of L1 and add add the new D to each L2. Obviously, I would rather have a master L2 that can just be updated once and have every A refer to that list, but I don't want to make some kind of global variable L2.
If I make a single instance of L2, do I just have to pass L2 to every A in L1, or can I get each A to refer to the single L2 without using a global variable?
java data-structures global-variables
java data-structures global-variables
asked Nov 15 '18 at 0:45
user2303321user2303321
9219
asked Nov 15 '18 at 0:45
user2303321user2303321
9219
asked Nov 15 '18 at 0:45
user2303321user2303321
9219
asked Nov 15 '18 at 0:45
user2303321user2303321
9219
asked Nov 15 '18 at 0:45
user2303321user2303321
9219
9219
Passing around a shared instance is not the same as a global variable, and seems like a perfectly appropriate solution.
– shmosel
Nov 15 '18 at 0:48
Sounds like you should pass the one L2 to every A as a constructor argument, but I can't be sure since you've omitted any information about what these things actually mean. The next time you ask a question like this, don't try to turn it into something so generic -- not all similar questions have the same answer.
– Matt Timmermans
Nov 15 '18 at 4:45
add a comment |
Passing around a shared instance is not the same as a global variable, and seems like a perfectly appropriate solution.
– shmosel
Nov 15 '18 at 0:48
Sounds like you should pass the one L2 to every A as a constructor argument, but I can't be sure since you've omitted any information about what these things actually mean. The next time you ask a question like this, don't try to turn it into something so generic -- not all similar questions have the same answer.
– Matt Timmermans
Nov 15 '18 at 4:45
Passing around a shared instance is not the same as a global variable, and seems like a perfectly appropriate solution.
– shmosel
Nov 15 '18 at 0:48
Passing around a shared instance is not the same as a global variable, and seems like a perfectly appropriate solution.
– shmosel
Nov 15 '18 at 0:48
Sounds like you should pass the one L2 to every A as a constructor argument, but I can't be sure since you've omitted any information about what these things actually mean. The next time you ask a question like this, don't try to turn it into something so generic -- not all similar questions have the same answer.
– Matt Timmermans
Nov 15 '18 at 4:45
Sounds like you should pass the one L2 to every A as a constructor argument, but I can't be sure since you've omitted any information about what these things actually mean. The next time you ask a question like this, don't try to turn it into something so generic -- not all similar questions have the same answer.
– Matt Timmermans
Nov 15 '18 at 4:45
add a comment |
1 Answer
1
active
oldest
votes
static variable is what you are looking for.
public class A {
private static final List<D> l2 = new ArrayList<>();
public void addD(D d) {
l2.add(d);
}
}
answered Nov 15 '18 at 0:52
KartikKartik
3,75731435
Ifl2is static,addD()should also be. But it's usually better to avoid global state.
– shmosel
Nov 15 '18 at 3:07
add a comment |
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1 Answer
1
active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
static variable is what you are looking for.
public class A {
private static final List<D> l2 = new ArrayList<>();
public void addD(D d) {
l2.add(d);
}
}
answered Nov 15 '18 at 0:52
KartikKartik
3,75731435
Ifl2is static,addD()should also be. But it's usually better to avoid global state.
– shmosel
Nov 15 '18 at 3:07
add a comment |
static variable is what you are looking for.
public class A {
private static final List<D> l2 = new ArrayList<>();
public void addD(D d) {
l2.add(d);
}
}
answered Nov 15 '18 at 0:52
KartikKartik
3,75731435
Ifl2is static,addD()should also be. But it's usually better to avoid global state.
– shmosel
Nov 15 '18 at 3:07
add a comment |
static variable is what you are looking for.
public class A {
private static final List<D> l2 = new ArrayList<>();
public void addD(D d) {
l2.add(d);
}
}
answered Nov 15 '18 at 0:52
KartikKartik
3,75731435
static variable is what you are looking for.
public class A {
private static final List<D> l2 = new ArrayList<>();
public void addD(D d) {
l2.add(d);
}
}
answered Nov 15 '18 at 0:52
KartikKartik
3,75731435
answered Nov 15 '18 at 0:52
KartikKartik
3,75731435
answered Nov 15 '18 at 0:52
KartikKartik
3,75731435
answered Nov 15 '18 at 0:52
KartikKartik
3,75731435
3,75731435
Ifl2is static,addD()should also be. But it's usually better to avoid global state.
– shmosel
Nov 15 '18 at 3:07
add a comment |
Ifl2is static,addD()should also be. But it's usually better to avoid global state.
– shmosel
Nov 15 '18 at 3:07
If
l2 is static, addD() should also be. But it's usually better to avoid global state.– shmosel
Nov 15 '18 at 3:07
If
l2 is static, addD() should also be. But it's usually better to avoid global state.– shmosel
Nov 15 '18 at 3:07
add a comment |
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Passing around a shared instance is not the same as a global variable, and seems like a perfectly appropriate solution.
– shmosel
Nov 15 '18 at 0:48
Sounds like you should pass the one L2 to every A as a constructor argument, but I can't be sure since you've omitted any information about what these things actually mean. The next time you ask a question like this, don't try to turn it into something so generic -- not all similar questions have the same answer.
– Matt Timmermans
Nov 15 '18 at 4:45