Method Return Type Changed

The return type of a method has been changed.

Example

The power() and factorial() methods have been defined in the Math class. The type of the power() method is changed from int to long, and the type of the factorial() method from long to int.

public interface Math {
-int power(int base, int power);
-long factorial(int n);
+long power(int base, int power);
+int factorial(int n);

}

Broken Uses

Hereafter, we list the broken uses that are currently detected by Maracas.

• 1. Invocations to the modified method
• 2. Methods overriding the modified method

1. Invocations to the modified method

Invocations to the method in a statement where the expected type is not compatible with the new type.

Example

Method displayPower()—defined in the Calculator class in a client project—invokes an implementation of the power() method. The long value is assigned to an int variable. Then, a broken use is reported pointing to the method invocation expression.

public class Calculator {
  public void displayPower(int base, int power) {
    Math math = new MathImpl();
    // Broken use reported here
    int result = math.power(base, power);
    System.out.println(result);
  }

}

2. Methods overriding the modified method

Methods overriding the modified method where the new type is not compatible with the client method type.

Example

The MathImpl class in a client project overrides the factorial() method. However, there is a mismatch between the return types of both methods. Then, a broken use is reported pointing to the client method declaration.

public class MathImpl implements Math {
  // Broken use reported here
  @Override
  public long factorial(int n) {
    if (n == 0)
      return Long.valueOf(1);

    return Long.valueOf(n * factorial(n - 1));
  }

}