Exercise – Shadowing

Write the code that demonstrates variable shadowing. We have not talked about it, so you will need to do some research.

Answer

Here is one possible solution:

public class ShadowingDemo {
  private String x = "x";
  public void printX(){
    System.out.println(x);   
String x = "y";
System.out.println(x);   
  }
}

If you run new ShadowingDemo().printX();, it will print x first, then y because the local variable x in the following line shadows the x instance variable:

String x = "y";

Please note that shadowing can be a source of a defect or can be used for the benefit of the program. Without it, you would be not able to use a local variable identifier that is already used by an instance variable. And here is another example of a case where variable shadowing helps:

private String x = "x";
public void setX(String x) {
  this.x = x;
}

The x local variable (parameter) shadows the x instance variable. It allows using the same identificator for a local variable name that has been...