Question

In the following code, which line has an error?

1. public interface Interface {
2. int FIELDA = 55;
3. public int methodA(double) {
4. }
5. }

A) Line 3

B) Line 1

C) Line 2

D) Line 4

Answer 1

Line 3 contains an error due to the absence of a parameter name in the method signature of an interface, which is required for the code to compile in Java. (option A is the correct answer)

Step-by-step explanation:

In the given code snippet, the error is in line 3. Method signatures in interfaces in Java must provide a name for each parameter type in the method signature. The correct method signature should include a parameter name, such as methodA(double value). Without the parameter name, the code will not compile.

As per the Java Language Specification, all method declarations in an interface, including default methods, must be fully abstract, except static methods. This means they should not provide an implementation, and the method signature in an interface should end with a semicolon.

returnType methodName(parameterType parameterName);

In Line 3, the methodA declaration lacks the method name, and there is an issue with the parameter declaration. It should be something like:

public returnType methodA(double parameterName);

Additionally, interface fields are implicitly public, static, and final, so there's no need for the "public" keyword in front of the method declaration. The corrected Line 3 would be:

int methodA(double parameterName);

The error is in Line 3, where the methodA declaration in the interface lacks a proper method signature. It should be corrected to have a valid return type, method name, and parameter type.