Is there any way to loop though variable names?

Question

So for example I have the following variables: Var1, Var2, Var3, Var4, Var5 - a total of 5 variables. All with unique data and I want to loop though them using a for loop.

//String Var1 = something, Var2 = something etc..
for (int i = 1; i <= 5; i++)
{
Var(i) = "something else";
}
//i.e I change Var(1), Var(2) etc.. to something else respectively.

To clarify further, ultimately I want to apply this method to iterate through multiple components in my program. I have a large number of components with styled names(e.g. label1, label2, label3 etc..) and want to change the value of these components without having to individually set their value.

Why does no one in [java] maintain canonical duplicates? Surely this is asked hundred times before. — BalusC, Oct 17 '15 at 11:32
Sounds like you are looking for a [Map](https://docs.oracle.com/javase/8/docs/api/java/util/Map.html) datastructure. — Gowtham, Oct 17 '15 at 11:37

score 10 · Accepted Answer · answered Oct 17 '15 at 11:11

10

You can do it with reflection, if the variables are defined as members of a class. For method parameters or local variables it is not possible. Something similar to this:

Class currentClass = getClass();
Field[] fields = currentClass.getFields();
for (Field f : fields) {
  System.out.println(f.getName());
}

If you intend to change the value it becomes a bit more complicated as you also have to consider the type of the variable. E.g. you can assign a String to a variable of type Object but not the other way around.

answered Oct 17 '15 at 11:11

hotzst

6,413
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I wonder why this is downvoted, since it's the only way to truly iterate through variables in Java. – MartinTeeVarga Oct 17 '15 at 11:31
Gotta laugh at the -1's for the only proper solution. – rustyx Oct 17 '15 at 11:34
Can I set variables to those class fields? IE, class has String point1, point2, point3; can I iterate through fields and set string? – Jeredriq Demas Jun 29 '20 at 11:36

score 5 · Answer 2 · answered Oct 17 '15 at 11:13

I would suggest to go for an array if data type of variables are same. You can try something like that

        String[] Var = {"something","something2","something else"};
        for (String var : Var)
        {
        System.out.println(var);
        }

Jiri Tousek · Answer 3 · 2015-10-17T12:13:50.507

1

You can't loop through (local) variables. You can use an array or a List and then loop through its elements:

for (Object item : myListOfObjects) {
    // do the processing
}

edited Oct 17 '15 at 12:13

answered Oct 17 '15 at 11:10

Jiri Tousek

11,783
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score 1 · Answer 4 · answered Oct 17 '15 at 11:29

As long as all the variables use the same type, you can use an Array to store all of them. Then you can use a for loop to iterate through the array. Something like this:

     String[] V = {"var1","var2","var3","var4","var5"};
    int arraylength = V.length;

    for(int i = 0; i<arraylength; i++){
        System.out.println(V[i]);
    }

score 0 · Answer 5 · answered Oct 17 '15 at 11:24

Using Java 8 Arrays it is as simple as:

Arrays.stream(varArray).forEach(System.out::println);

Usage:

public class LoopVariables {
    public static void main(String[] args) {
        String[] varArray = new String[]{"Var1", "Var2", "Var3", "Var4", "Var5"};
        Arrays.stream(varArray).forEach(System.out::println);
    }
}

score -2 · Answer 6 · edited Nov 26 '17 at 09:47

Try This piece of Code.

public class Main {

    public static void main(String[] args) {
        Insan i1[]=new Insan[5];
        i1[0].name="Ali";
        i1[0].age=19;
        i1[1].name="Pakize";
        i1[1].age=29;
        i1[2].name="Kojiro Hyuga";
        i1[2].age=30;
        i1[3].name="Optimus Prime";
        i1[3].age=40;
        for (int ib=0; ib < 4; ib++) {
            System.out.println("Name: " + i1[ib].name + " Age: "+i1[ib].age);
        }

    }
}

Is there any way to loop though variable names?

6 Answers6

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