Practice with Functions and Strings
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Algorithmic Thinking and Problem Solving
But First: More About Functions
Java Method Overloading
I told you that functions couldn’t have the same name.
I lied.
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Java Method Overloading
Java uses both the function name and the the list of arguments and types to determine which function to call.
Together they are called the function signature.
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Does the function have the right name?
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Does the function take the right arguments in the right order?
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Java will also try to convert types to find a match as long as no loss of precision occurs
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Function Input Validation
A common function design pattern is to check your inputs at the top.
Think about all the bad inputs you could possibly get from the caller.
int sum(int[] numbers) {
// check numbers to make sure it's sane
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null Arrays
What is the value of array declared below?
int[] output = null;
System.out.println(output);-
Java has a special value that can be used to indicate that an object has not been initialized:
null. -
nullis not a valid object: it has no properties or methods that you can use. -
Attempts to use
nullwill result in an error
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Defensive Programming 101
Always check objects for null.
Let’s Solve Some Problems!
Consecutive Identical Values
Given a string, write a function to find all cases where consecutive characters are the same.
First, what is our algorithm?
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Examine each character in the array
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Compare it with the next character—but how do we get at that?
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Print it out if they are the same
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Testing
Test cases are an indispensable part of modern software development.
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To perform a simple test, pick a input that you know the answer to and check that your function returns the expected value.
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Try to pick cases that are hard and where you might not get the right answer—we call these corner cases.
Announcements
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Quiz 2 starts today in the CBTF. It covers arrays, functions, and strings.
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The fifth set of Turing’s Craft exercises (TC 5) will be out shortly and due Sunday by midnight.
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MP1 is due today! Office hours until 5PM today.
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MP2 will be out today and due next week—it’s another new challenge.