All Flashcards
What does the following code output? Student s = new Student(9, "Jane Doe", 14); s.setGradeLevel(10); System.out.println(s.getGradeLevel());
10
Identify the error in the following code: public class Example { private int value; public void setValue() { value = 10; } }
The setValue method requires a parameter to set the value. It should be public void setValue(int newValue).
What does the following code output? Student s = new Student(9, "Jane Doe", 14); s.setName("Jane Smith"); System.out.println(s.getName());
Jane Smith
Complete the following code snippet to create a mutator method for the 'age' instance variable in the Student class: public class Student { private int age; // Complete the mutator method here }
public void setAge(int newAge) { age = newAge; }
What does the following code output? Student s = new Student(10, "Alice", 15); s.setGradeLevel(11); Student t = s; t.setGradeLevel(12); System.out.println(s.getGradeLevel());
12
Identify the error in the following code: public class Student { private String name; public String setName(String newName) { name = newName; } }
The return type of the setName method should be void, not String.
What does the following code output? Student s = new Student(9, "Jane Doe", 14); s.setName(null); System.out.println(s.getName());
null
Complete the following code snippet to add a validation check in the setGradeLevel mutator method: public class Student { private int gradeLevel; public void setGradeLevel(int newGradeLevel) { // Add validation check here } }
if (newGradeLevel >= 9 && newGradeLevel <= 12) { gradeLevel = newGradeLevel; }
What does the following code output? Student s = new Student(10, "Alice", 15); s.setGradeLevel(11); System.out.println(s.toString());
The output will vary depending on the implementation of the toString method in the Student class, but it will include the updated gradeLevel (11) and the student's other attributes.
Identify the potential issue in the following code: public class Student { private String name; public void setName(String newName) { name = newName.trim(); } }
If newName is null, newName.trim() will throw a NullPointerException. A null check should be added before calling trim().
What are the general steps to write a mutator method?
- Determine the instance variable to modify. 2. Define the method signature (public void setVariableName(DataType parameterName)). 3. Implement the method body to assign the parameter value to the instance variable. 4. Add any necessary validation or error checking.
What is the process of using a mutator method to update an object's state?
- Create an instance of the class. 2. Call the mutator method on the object, passing the new value as a parameter. 3. The object's state is updated internally.
What are the steps to determine if a class should have a mutator method for a specific instance variable?
- Analyze the requirements of the class and its intended use. 2. Determine if external clients should be allowed to modify the value of the instance variable. 3. Consider the potential impact of modifications on the object's state and data integrity. 4. If modifications are necessary and safe, create a mutator method; otherwise, leave the instance variable immutable.
What are the steps involved in validating input within a mutator method?
- Receive the input parameter. 2. Check if the input meets the required criteria (e.g., data type, range, format). 3. If the input is invalid, either reject the input (throw an exception or return an error code) or sanitize the input (e.g., trim whitespace, convert to a valid format). 4. If the input is valid, assign it to the instance variable.
What is the process of deciding whether a mutator method should return a value or be void?
- Determine if the client needs to know the previous value of the instance variable. 2. If the client needs the previous value (e.g., for undo functionality), return the previous value. 3. If the client does not need the previous value, make the method void.
What are the steps to ensure thread safety when using mutator methods in a multithreaded environment?
- Identify the instance variables that are accessed and modified by multiple threads. 2. Use synchronization mechanisms (e.g., locks, mutexes) to protect access to these variables. 3. Ensure that mutator methods are atomic (i.e., they perform a single, indivisible operation). 4. Avoid race conditions and data corruption by properly synchronizing access to shared resources.
What are the steps to document a mutator method effectively?
- Write a clear and concise description of the method's purpose. 2. Specify the input parameters and their expected values. 3. Describe the effect of the method on the object's state. 4. Document any exceptions that may be thrown. 5. Provide examples of how to use the method.
What are the steps to test a mutator method thoroughly?
- Create test cases that cover different input values, including valid, invalid, and boundary values. 2. Verify that the object's state is updated correctly after calling the mutator method. 3. Check that any validation logic is working as expected. 4. Test the method in different scenarios, such as with null or empty inputs.
What are the steps to refactor a class to add or modify mutator methods?
- Analyze the existing code and identify the instance variables that need to be modified. 2. Create or modify the mutator methods to provide the necessary functionality. 3. Update any code that uses the class to use the new or modified mutator methods. 4. Test the changes thoroughly to ensure that they do not introduce any regressions.
What are the steps to handle exceptions within a mutator method?
- Identify the potential exceptions that may be thrown (e.g., IllegalArgumentException, NullPointerException). 2. Use try-catch blocks to handle the exceptions. 3. In the catch block, either log the exception, re-throw the exception, or take corrective action (e.g., set the instance variable to a default value). 4. Ensure that the exception handling logic does not introduce any new issues.
What is a mutator method?
A method that changes the values of instance variables of an object.
What is another name for mutator methods?
Setter methods.
What does 'void' mean in the context of a method?
The method does not return any value.
What is an immutable class?
A class with no mutator methods, meaning its state cannot be changed after creation.
What is the typical return type of a mutator method?
void
What is the purpose of a parameter in a mutator method?
To provide the new value to which the instance variable will be set.
What is an instance variable?
A variable defined in a class for which every object of the class has its own copy.
What is the difference between accessor and mutator methods?
Accessor methods retrieve the values of instance variables, while mutator methods modify them.
Why might a class not have a mutator method for a specific instance variable?
To prevent clients from changing the data of that instance variable, ensuring data integrity.
What is the signature of a mutator method?
Typically 'public void methodName(DataType parameterName)'