CODEWITHSUNDEEP
javavariables
Paul T.
Paul T.

Reputation: 31

Setting variable values to be based on other variables

Say we have variables int a = 0; and int c;. Is it possible to make it so that c is always equal to something like a + 1 without having to redundantly retype c = a + 1 over and over again

Thanks!

Upvotes: 0

Views: 162

Answers (3)

chengpohi
chengpohi

Reputation: 14217

Firstly, The answer is no, you can't do it directly in Java, but you can redesign your int class, There is an example:

public class Test {
    public static void main(String[] args) throws IOException {
        MyInt myInt1 = new MyInt(1);
        KeepIncrementOneInt myInt2 = new KeepIncrementOneInt(myInt1);
        System.out.println(myInt2.getI());
        myInt1.setI(2);
        System.out.println(myInt1.getI());
        System.out.println(myInt2.getI());
    }
}
class MyInt { //your own int class for keep track of the newest value
    private int i = 0;
    MyInt(int i) {
        this.i = i;
    }
    public int getI() {
        return this.i;
    }
    public void setI(int i) {
        this.i = i;
    }
}
class KeepIncrementOneInt { //with MyInt Class to get the newest value
    private final MyInt myInt;
    KeepIncrementOneInt(MyInt myInt) {
        this.myInt = myInt;
    }
    public int getI() {
        return this.myInt.getI() + 1; //get the newest value and increment one.
    }
}
  • Create your own Int class, because we need a reference type to keep track of the newest the value a. like the MutableInt in apache commons.
  • Create a always increment 1 class with your own Int class as a member.
  • In getI method, it's always from the reference Int class get the newest value a.

Upvotes: 1

Vladimir Vagaytsev
Vladimir Vagaytsev

Reputation: 2891

Since you have 2 variables tied in a specific way, consider using custom object to wrap a and c values. Then you can control the object state inside the class logic. You can do something like this:

public class ValuePair {

    private final int a;
    private final int c;

    public ValuePair(int a) {
        this.a = a;
        this.c = a + 1;
    }

    public int getA() {
        return a;
    }

    public int getC() {
        return c;
    }
}

Upvotes: 1

Sergey Kalinichenko
Sergey Kalinichenko

Reputation: 726479

No, it is not possible to make one variable track another variable. Usually, this is not desirable either: when a value of one variable is tied to the value of another variable, you should store only one of them, and make the other one a computed property:

int getC() { return a+1; }

A less abstract example is a connected pair of age and date of birth. Rather than storing both of them, one should store date of birth alone, and make a getter method for computing the current age dynamically.

Upvotes: 3

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