Lecture 8 | Programming Methodology (Stanford) | Summary and Q&A

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July 2, 2008
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Stanford
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Lecture 8 | Programming Methodology (Stanford)

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Summary

In this video, they discuss the concept of information hiding in software engineering, using the analogy of a toaster to explain the principle. They also talk about the difference between local variables and instance variables and how to use the random generator class as an instance variable in a program.

Questions & Answers

Q: What is the principle of information hiding in software engineering?

The principle of information hiding is about encapsulating complexity and hiding it from the user by providing a simple interface. This allows the user to use the method or class without needing to know the internal details.

Q: How does the analogy of a toaster explain information hiding?

The analogy of a toaster shows how the user doesn't need to know the internal workings of the toaster to use it. They just need to know how to operate it (putting in bread and pressing a button) and they receive the desired output (toast). The complexity of how the toaster works is hidden from the user.

Q: Why is information hiding important in software engineering?

Information hiding is important because it allows for modularity and abstraction in software design. It allows developers to create modules that solve specific problems and can be reused without the user needing to understand the internal details. It also provides flexibility to change the implementation without affecting the user.

Q: Can you provide another example of information hiding?

One example of information hiding is the readInt method in Java. The user can simply call this method to read an integer input from the user, without needing to know how the method performs error checking or retrieves the input. The implementation details are hidden, and the user can focus on using the method to get the desired input.

Q: How are local variables different from instance variables?

Local variables are declared inside a method and are only visible and accessible within that method. They have a limited lifetime and are destroyed after the method finishes execution. Instance variables, on the other hand, are declared in a class but not inside a method. They are visible to all methods in the class and are shared among them. They have a longer lifetime and exist as long as the object exists.

Q: When should you use local variables?

Local variables should be used when you need a variable to perform a specific computation within a method and you don't need the value outside of that method. They are suitable for storing temporary values or computations that are only relevant within the method.

Q: When should you use instance variables?

Instance variables should be used when you need to store values that are relevant to the state of the object. They are suitable for storing data or information that needs to be accessed or modified by multiple methods within the class.

Q: How do you declare an instance variable of type random generator?

To declare an instance variable of type random generator, you would include the following line in your class: private random generator ourGen = random generator.get instance();. This line initializes the instance variable ourGen with an instance of the random generator class using the get instance() method.

Q: What are some methods available in the random generator class?

Some methods available in the random generator class include nextInt(range), nextDouble(range), nextDouble(), nextBoolean(), and nextColor(). These methods allow you to generate random integers, doubles, booleans, and colors based on different ranges or probabilities.

Q: How can you use the random generator as an instance variable in a program?

To use the random generator as an instance variable in a program, you would declare it at the class level (outside of any methods) and initialize it with an instance using the get instance() method. Once initialized, you can use the instance variable in any method within the class to generate random numbers or perform other random operations.

Takeaways

The principle of information hiding in software engineering is about encapsulating complexity and providing a simple interface to the user, hiding all the internal details. This allows for modularity, abstraction, and reusability of code. Local variables are declared inside a method and are only accessible within that method, while instance variables are declared in a class and are visible to all methods in the class. Instance variables are used to store data that is relevant to the state of the object. The random generator class can be used as an instance variable to generate random numbers or perform other random operations in a program.

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