Can I use value of a local variable defined in a method, in other method in Java?

Issue

The method is not returning the value of the local variable.

Can I use the value of local variable index from the following method

public boolean contains(Object input) {
    int index = 0;

    while(myAsetIterator.hasNext()) {
        index++;
        if(input.equals(myAsetIterator.next())) {
            return true;
        }
    }
    return false;
}

in this method as the index of the array of the object that I want to remove.

public boolean remove(Object o) {
    int count = 0;
    if(o == null) {
        return false;
    }
    if(contains(o)) {
        genArray[index] == null;
    }
    if (count > 0) {
        System.out.println(count+" same elements were present in Aset. "
                + "Removed all those "+count+" elements from Aset.");
        return true;
    }
    return false;
}

I know the scope of a local variable is limited to the method it's declared in. But there might be a way that I might not now yet to make this happen without using a field/instance variable.

Solution

No. The whole point of it being local to a method is that it only exists within that method. The options are:

• Use an instance field, i.e. make it part of the state of the object. That's unlikely to be appropriate.
• Use a static field, i.e. make it part of the static of the type. That's almost certainly inappropriate.
• Change the existing method to return the information you want.
• Create a new method to return the information you want.
• Duplicate the existing code within remove so that you can get the index. That would be sad :(

As an example of the last two, you could write:

public int indexOf(Object input) {       
    int index = 0;    
    while(myAsetIterator.hasNext()) {
        index++;
        if (input.equals(myAsetIterator.next())) {
            return index;
        }
    }
    return -1;
}

public boolean contains(Object input) {
    return indexOf(input) == -1;
}

... then in your remove method, you'd use indexOf instead of contains.

Answered By - Jon Skeet