Question

I’ve a concrete class A that implements an interface B.

B ref = new A();

Code :

public interface B{
  public abstract String[] getWords();
}

public class A implements B {
  private String[] words = new String[] {};
  public void setWords(String[] words){
    this.words = words;
  }
  public String[] getWords(){
    return this.words;
  }
 }

In the interface B, I’ve only getter method but no setter method though the class A has it.

So when I do this : B ref = new A();, will this code work and how will I set words?

Answer 1

You have to cast back to the original type if the interface does expose it

if (ref instanceof A)
   ((A) ref).setWords(words);
else
   // something else.

A better solution is to add the method to the interface.