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generic implementation for future flexibility

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Last Modified: 2019-01-10
public class CollectionsRef {
 
    private HashSet<Integer> numbers;
 
    public ArrayList<String> getList() {
 
        return new ArrayList<String>();
    }
 
    public void setNumbers(HashSet<Integer> numbers) {
        this.numbers = numbers;
    }
}
Look at the reference types which are collection implementation classes - this locks the code to work with only these classes HashSet and ArrayList. What if we want the method getList() can return a LinkedList and the method setNumbers() can accept a TreeSet?
The above class can be improved by replace the class references to interface references like this:
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public class CollectionsRef {
 
    private Set<Integer> numbers;
 
    public List<String> getList() {
        // can return any kind of List
     [b]   return new ArrayList<String>();[/b]
    }
 
    public void setNumbers(Set<Integer> numbers) {
        // can accept any kind of Set
        this.numbers = numbers;
    }
}

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can we have generic List as return type to provide more flexibility to future changes to collection implementation?
https://www.codejava.net/coding/10-java-core-best-practices-every-java-programmer-should-know
Please advise
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